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3D SURFACE MICRO TOPOGRAPHY RECOVERY FROM MULTI-FOCUS IMAGE SEQUENCE USING OMNIDIRECTIONALMODIFIED LAPLACIAN OPERATOR WITH ADAPTIVE WINDOW SIZE

Ying Zhong Tian, Huijuan HU, Haoyang CUI, Shouchen YANG, Ji QI, Zhiming XU, and Long Li

Doc ID: 290341 Received 24 Mar 2017; Accepted 22 Jun 2017; Posted 22 Jun 2017  View: PDF

Abstract: Optical microscopy enables the observation of highly magnified objects and material structures on micro surfaces, however with the weakness that it can only acquire 2D images. In order to observe areal features more accurately and intuitively, 3D surface micro topography recovery is applied to form a 3D surface model of an object from its 2D image sequence. In the 3D reconstruction of the focus evaluation operator, there are gray variance operator, grayscale differenceabsolute sum operator, Roberts gradient operator, Tenengrad gradient operator, improved Laplace operator and so on.There are two problems with these operators: one is that there is no difference between (x, y) and the gray scale of the pixel in the diagonal direction in the field.The second is that the window size of the focus evaluation operator is fixed, such as 3×3, 5×5, etc.,the size of the window for each pixel in the image is the same, and the small window may not cover enough field information, but also vulnerable to noise, large windows cover more information, but may cause a smooth phenomenon, affecting the accuracy of the model, and different pixels around the field of pixel color difference is different, the size of the window is not the same.Therefore, this paper proposes a modified omnidirectional Laplacian operator with adaptive window, which can automatically adjust the size of the window according to the color difference within the window, and also takes into account the pixels on the diagonal. In addition, very comprehensive verification experiments are conducted to prove the conclusions.

Optical properties of a dichroic dye-doped liquid-crystal grating and its application to optical rotation measurement

Michinori Honma, Natsuki Takahashi, and Toshiaki Nose

Doc ID: 291933 Received 31 Mar 2017; Accepted 22 Jun 2017; Posted 22 Jun 2017  View: PDF

Abstract: The diffraction properties of a twisted nematic liquid-crystal (TN-LC) grating, in which a dichroic dye was doped, were investigated experimentally in terms of the applicability to an optical system for determining the polarization angle of incident linearly polarized light. The main reason to dope a nematic LC material with a dichroic dye was to enhance the polarization dependence of the diffracted light intensities for the positive and negative first orders. We found the best values of the applied voltage and dye concentration for application in polarization angle measurement. The TN-LC grating with a high polarization sensibility was applied to the optical system for measuring the concentration of an optically active component in a liquid specimen. As a result, the applicability of the proposed optical system was revealed experimentally. Furthermore, the cause of the random measurement error was discussed briefly.

Multiple-3D-object decryption based on one interference using two phase-only functions

Wei-Na Li, Sang-Min Lee, Sangkeun Gil, and Nam Kim

Doc ID: 292753 Received 12 Apr 2017; Accepted 22 Jun 2017; Posted 22 Jun 2017  View: PDF

Abstract: We propose a multiple-3D-object decryption scheme based on one interference using two phase-only functions. It takes advantage of off-axis digital holography to encrypt multiple 3D objects into one mutual ciphertext, and utilizes different decryption keys to decrypt each 3D object, respectively. The advantages of the proposed scheme include the following: each 3D object can be decrypted discretionarily without decrypting a series of other objects earlier; no iterative algorithm is involved; the decrypted image of each object can be successfully clearly distinguished. The feasibility of the proposed scheme is verified by the optical holograms of real 3D objects.

Beam steering limitation of Risley prism system due tototal internal reflection

Zhou Yuan, Shixun Fan, Ying chen, Xiaoxia Zhou, and Guangcan Liu

Doc ID: 293456 Received 24 Apr 2017; Accepted 22 Jun 2017; Posted 22 Jun 2017  View: PDF

Abstract: Limitations of beam steering in Risley prisms, induced by total internal reflection, are investigated for the fourtypical configurations. The incident angles at the exit surfaces of double prisms are calculated by nonparaxial raytracing and compared with the critical angle. On this basis, the limitations of opening angle, relative orientation ofthe prisms and ray deviation power of the system are derived. It is shown that the ray deviation power reaches itsextreme value when the opening angles increase to a certain limit value for a given prism material. As the openingangles exceed the limit value, the prisms’ relative orientation is limited. With the increase in refractive index, thelimit value of opening angles decreases while the extreme value of deviation power increases. In comparison to 21-12, 12-12 configuration, 21-21, 12-21 configuration has a larger limit value of opening angles and also a largerextreme value (90º) of deviation power, so that they leave a wider margin for the design of wide-angle beamsteering system. The research can afford guidance for prism material and geometry choices in the design of wideangleRisley-prisms-based beam steering system.

Correcting groove error in gratings ruled on a 500-mmruling engine using interferometric control

xiaotao mi, haili yu, hongzhu Yu, Shanwen Zhang, xiaotian li, Xuefeng Yao, Xiangdong Qi, heshig bayan, and WAN Hua

Doc ID: 294616 Received 27 Apr 2017; Accepted 22 Jun 2017; Posted 22 Jun 2017  View: PDF

Abstract: Groove error is one of the most important factors affecting grating quality and spectral performance. To reducegroove error, we propose a new ruling-tool carriage system based on aerostatic guideways. We design a new blankcarriage system with double piezoelectric actuators. We also propose a completely closed-loop servo-controlsystem with a new optical measurement system that can control the position of the diamond relative to the blank.To evaluate our proposed methods, we produced several gratings, including an echelle grating with 79grooves/mm, a grating with 768 grooves/mm, and a high-density grating with 6000 grooves/mm. The results showthat our methods effectively reduce groove error in ruled gratings.

Multilayer-coated photodiode-based beam intensitymonitor for polarization analysis of plasma soft X-raylaser

Takashi IMAZONO

Doc ID: 288011 Received 23 Mar 2017; Accepted 22 Jun 2017; Posted 23 Jun 2017  View: PDF

Abstract: A Mo/Si multilayer-coated photodiode detector (MP) for beam-intensity monitoring was prototyped andcharacterized using synchrotron radiation and X-ray laser (XRL) sources, in order to perform polarization analysisof a laser-driven plasma soft XRL generated from nickel-like silver plasma. At a wavelength of 13.9 nm and an angleof incidence of 45°, the s-polarization reflectance is 0.525 and shows a strong positive correlation with thetransmittance corresponding to the photodiode current generated by the MP. We succeeded in performingpolarization analysis of XRL beams with a large shot-to-shot intensity variation using the MP. Thus, this MP enablesshot-to-shot monitoring and delivery of high intensity beams for downstream XRL experiments.

All-Fiber Multimode Interferometer for the Generation of a Switchable Multi-Wavelength Thulium-doped Fiber Laser

Harith Ahmad, Anir Syazwan Sharbirin, Muhamad Zharif Samion, and MOHAMMAD FAIZAL ISMAIL

Doc ID: 296400 Received 22 May 2017; Accepted 22 Jun 2017; Posted 23 Jun 2017  View: PDF

Abstract: A compact all-fiber MMI design to produce a switchable multi-wavelength TDFL is proposed and demonstrated. The TDFL fiber ring cavity employs a 60 cm length of multimode fiber into the cavity to induce multimode interference and provide intensity-dependent loss in order to generate a multi-wavelength output. The suppression of mode-competition and the overall stability of the TDFL is further improved by exploiting the filtering capability of a Sagnac loop. By increasing the pump power, a switchable wavelength output is allowed with a wavelength spacing of ~1.8 nm. At 361 mW input pump power, nine laser lines are generated, with a maximum SMSR value of ~36 dB and an output power of 3.3 mW. The multi-wavelength TDFL also exhibit great stability in one-hour operation with a minimal wavelength drift of 0.2 nm. The proposed multi-wavelength TDFL has a potential to be employed in future Thulium-doped Fiber Amplifier (TDFA) based telecommunication infrastructure and also has the possibility to be applied in areas such as sensing and spectroscopy largely associated with its two-micron wavelength output.

An Improved Laser-Based Triangulation Sensor withEnhanced Range and Resolution through AdaptiveOptics-Based Active Beam Control

Syed Reza, Tariq Khwaja, Mohsin Ali Mazhar, Haris Niazi, and Rahma Nawab

Doc ID: 293446 Received 25 Apr 2017; Accepted 21 Jun 2017; Posted 22 Jun 2017  View: PDF

Abstract: Various existing target ranging techniques are limited in terms of the dynamic range of operation andmeasurement resolution. These limitations arise as a result of a particular measurement methodology, the finiteprocessing capability of the hardware components deployed within the sensor module and the medium throughwhich the target is viewed. Generally, improving the sensor range adversely affects its resolution and vice versa.Often, a distance sensor is designed for an optimal range/resolution setting depending on its intended application.Optical triangulation is broadly classified as a spatial signal processing-based ranging technique and measurestarget distance from the location of the reflected spot on a Position Sensitive Detector (PSD). In most triangulationsensors that use lasers as light source, beam divergence – which severely affects sensor measurement range – isoften ignored in calculations. In this paper, we first discuss in detail the limitations to ranging imposed by beamdivergence which, in effect, set the sensor dynamic range. Next, we show how the resolution of laser-basedtriangulation sensors is limited by the inter-pixel pitch of a finite-sized PSD. In this paper, through the use ofTunable Focus Lenses (TFLs), we propose a novel design of a triangulation-based optical rangefinder whichimproves both the sensor resolution and its dynamic range through adaptive electronic control of beampropagation parameters. We present the theory and working of the proposed sensor and clearly demonstrate arange and resolution improvement with the use of TFLs. Experimental results in support of our claims are shown tobe in strong agreement with theory.

Magnetically tunable enhanced absorption of circularly polarized light in graphene-based 1D photonic crystals

Arezou Rashidi, Abdolrahman Namdar, and Reza Abdi-Ghaleh

Doc ID: 293213 Received 19 Apr 2017; Accepted 20 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: We theoretically investigate the magnetic field induced terahertz absorption enhancement of a graphene-based one-dimensional photonic crystal using 4×4 transfer matrix method for circular polarization of light. The results show that the magnetically tunable absorption of the structure depends on the circular polarization state, magnetic circular dichroism, and interestingly absorption behaviors of right-handed and left-handed circularly polarized light interchange by changing the direction of the magnetic field. Theses properties can be used to design the circular polarization based sensors.

Image quality and spectral performance evaluations inthe polarization imaging spectrometer based onSavart polariscope

Peng Gao, Jingjing Ai, Qingying Chen, and Shuaiyi Zhang

Doc ID: 290979 Received 20 Mar 2017; Accepted 20 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: The modulation transfer function (MTF) and signal-to-noise ratio (SNR) are the key parameters to evaluatequantitatively the image quality and spectral performance in the polarization imaging spectrometer basedon Savart polariscope. In order to evaluate the image quality and reflect the detecting ability of the imagingspectrometer, the calibration experiments on the MTF, SNR and spectral resolution were carried out andsome important conclusions were obtained. If the incident radiance were 4.464 w m2 ⋅ sr , 3.119 w m2 ⋅ sr and0.5 w m2 ⋅ sr , the average SNR of the interferogram were 500 dB, 400 dB and 200 dB, respectively, and theMTF is 0.24. During the spectral resolution calibration, the maximum optical path difference (OPD) was set as57.08 um, and the measured value is greater than the theoretical value, which is mainly caused by thestructural design of the polarization imaging spectrometer. For the wavelength range of [500nm,600nm] , theSNR of the spectrum is lower and about 50 dB, while the SNR is obviously higher in a range ofλ ∈[600nm,960nm] . This study provides a theoretical and practical guidance for improving the image qualityand judging the spectral performance of the polarization imaging spectrometer.

Optical Limiting Performance of a GaAs/AlAs Heterostructure Microcavity in the Near-Infrared

Anton Ryzhov

Doc ID: 292046 Received 07 Apr 2017; Accepted 20 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: A multilayer GaAs/AlAs heterostructure forming a Fabry--Perot microcavity with a narrow resonance at 1.1 μm was produced by molecular-beam epitaxy. Under nanosecond pulsed laser radiation, a blue shift of the resonant line, associated with a photo-induced negative change in refractive index in GaAs, was experimentally registered by using an optical parametric oscillator. The spectral shift was accompanied by a reduction in peak transmittance, associated with nonlinear intracavity absorption. Such a cavity can be used as an optical limiter at the resonant wavelength when both the spectral shift and the transmittance reduction contribute to the limiting effect. An exceptionally low limiting threshold of about 1 mJ/cm² was observed in the experiment.

Asymmetric Transmission of Obliquely Intersecting Nanoslit Arrays in a Gold Film

YuYan Chen, Yongkai Wang, Tiankun Wang, Yongyuan Zhang, Li Wang, and Zhongyue Zhang

Doc ID: 292800 Received 13 Apr 2017; Accepted 20 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: Asymmetric transmission (AT) has significant applications in optical polarization control. In this paper, we propose a kind of periodic nanoslits rather than the protruding planar structures, such as G-shaped structure and coupled split-ring resonators, to realize the AT effect. The planar periodic obliquely intersecting nanoslits (OINs) in the gold film, composed of gratings with an infinite length and tilted nanoslits with a finite length, are proposed to realize AT effect by performing the finite element method. Obvious dips in the AT spectra result from the circular localized surface plasmon resonance around the two terminals of the tilted nanoslits and from the surface plasmon polariton resonances on the film and in the gratings or tilted nanoslits. In addition, the AT effect strongly depends on the geometric parameters of the OINs. The film can be straightly powered on as an in-plane electrical conductor, which broadens its applications in optoelectronic devices. Overall, these results are beneficial in designing devices to achieve AT for polarization transformation.

Experimental validation of nonlinearity suppression for an inverse-layer-type silicon photodiode and its prediction based on theoretical modeling

Minoru Tanabe, Tatsuya Zama, and Hiroshi Shitomi

Doc ID: 292822 Received 13 Apr 2017; Accepted 20 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: The spectral nonlinearity of an inverse-layer-type silicon (Si) photodiode (PD) in the visible region was investigated. As expected by theoretical calculation, supralinearity and saturation of the Si PD, which are key factors of nonlinearity, were suppressed by applying a reverse voltage above 30 V. Experimentally observed nonlinear behavior depending on the reverse bias was compared with a theoretical model describing supralinearity, including the inner parameters of the Si PD, and these comparison results were in agreement. This theoretical model enables us to quantitatively predict the behavior of the supralinearity of the inverse-layer-type Si PD in various reverse bias conditions. Accurate experimental nonlinearity supported by theoretical predictions will contribute to high-accuracy optical measurement with the Si PD over a wide range of optical power levels and various reverse-bias voltages.

Simple and flexible phase compensation for digital holographic microscopy with electrically tunable lens

DingNan Deng, Junzheng Peng, Weijuan Qu, Yu Wu, Xiaoli Liu, Wenqi He, and Xiang Peng

Doc ID: 293011 Received 27 Apr 2017; Accepted 19 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: In digital holographic microscopy (DHM) system, different microscope objectives (MOs) will introduce different phase distortions and thus lead to measurement errors. To address this problem, we present a simple and flexible method to compensate all phase distortions by introducing an electrically tunable lens (ETL) in the reference arm for a DHM system with multiple MOs. By exactly control the external currents of the ETL, we can change the reference wave front to match the wave front introduced by different MOs without complex alignment or additional numerical post-processing manipulations. This method is suitable for quantitative real-time phase imaging especially when it refers to multiple MOs. To demonstrate the validity and effectiveness of our scheme, we did a series of simulations and carried out some real experiments with two different MOs (4× and 10×).

Enhanced luminescence at 2.7 μm of Na5Lu9F32 singlecrystals co-doped Er3+/Pr3+ grown by Bridgmanmethod

Qingyang Tang, Haiping Xia, Jianli Zhang, and Baojiu Chen

Doc ID: 292749 Received 12 Apr 2017; Accepted 19 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: Na5Lu9F32 single crystals co-doped with 1 mol% Er3+ and various concentrations (0.1 mol%, 0.3 mol%, 0.5 mol%,0.7 mol% and 1 mol%) of Pr3+ were successfully grown by Bridgman method. The optical spectroscopicinvestigations of the obtained single crystal were reported for the absorption, emission and luminous decay. Theobtained single crystal appears almost no absorption at 2.7 μm band ascribing to OH- bond. According to the Judd-Ofelt (J-O) theory, the J-O intense parameters of Er3+ ions were calculated. Under the 980 nm LD pumping, anobviously enhanced emission at 2.7 μm was obtained in the Er3+/Pr3+ co-doped crystal compared with Er3+ singlydoped one due to the energy transfer from Er3+ to Pr3+. The intensest emission at 2.7 μm was obtained when thedoping concentrations of Er3+ and Pr3+ were 1 mol% and 0.5 mol% in present research. The maximum emissioncross-section and gain cross-section at 2.7 μm were also estimated. Moreover, using the Dexter theory, the energytransfer microscopic parameters have been calculated and the decay curve fitting using Inokuti-Hirayamaexpression indicated the dipole-dipole energy transfer from Er3+ to Pr3+ ions.

Uncertainty analysis for the determination of B4Coptical constants by angle-dependent reflectancemeasurement for 40 nm to 80 nm wavelength

Alexander Gottwald, Karl Wiese, Udo Kroth, and Mathias Richter

Doc ID: 290264 Received 08 Mar 2017; Accepted 19 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: The index of refraction and the extinction coefficient for thin films of boron carbide was determined by angledependentreflectance measurements in the vacuum-ultraviolet spectral range. The numerical approximation wasdone using transfer-matrix formalism in combination with particle swarm optimization for the fitting algorithm.By this, not only for the reflectance measurement but also for the numerical approximation, a profounduncertainty budget was developed. This includes possible effects due to contamination and intermediate layers.Thus it was possible to establish a method for determination of n and k with reliable and highly traceableuncertainties, and to significantly improve the consistency of existing data required for current developments inoptical technology.

Depth-of-field extension in integral imaging using multi-focus elemental images

Miao Zhang, Chuanzhen Wei, Yongri Piao, and Jianqiao Liu

Doc ID: 294654 Received 27 Apr 2017; Accepted 19 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: In integral imaging, one of the main challenges is the limited depth of field (DOF) which is mainly caused by theshort focus length of the microlenses. In this paper, we propose a new method to extend the depth of field of thesynthetic aperture integral imaging system by realizing the image fusion method on the multi-focus elementalimages with different perspectives. In the proposed system, the contour based object extraction method combinedwith size correction is developed to solve size inconsistency of the objects in the misaligned elemental images. Theall-in focus elemental images combining selected features of multi-focus elemental images are then obtained by theblock based image fusion method. At the last step, the reconstructed images with the extended DOF can begenerated based on the all-in focused EIs in the SAII system. Experimental results are presented to demonstrate thefeasibility of the proposed system.

Experimental optical encryption of gray scale information

Alejandro Velez, John Barrera Ramírez, and Roberto Torroba

Doc ID: 294845 Received 28 Apr 2017; Accepted 19 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: In this paper, we present a new protocol for achieving a lower noise and consequently a higher dynamic range in optical encryption. This protocol allows securing and optimal recovery of any arbitrary gray scale images encrypted using an experimental double random phase mask cryptosystem. The protocol takes advantage of recent advances that help reduce the noise due to the correlation of random phase mask in the decryption procedure, and introduces the use of a “reference mask” as a reference object used to eliminate the noise due to the complex nature of the masks used in experimental DRPE setups. This noise reduction increases the dynamic range of the decrypted data, retaining the gray scale values to a higher extent, and opening new possible applications. We detailed the procedure and we present experimental results, including an actual experimental video of a grayscale scene, confirming the validity of our proposal.

Transfer matrix method for four-flux radiative transfer

Brian Slovick, Zachary Flom, Lucas Zipp, and Ravi Krishnamurthy

Doc ID: 296281 Received 18 May 2017; Accepted 19 Jun 2017; Posted 21 Jun 2017  View: PDF

Abstract: We develop a transfer matrix method for four-flux radiative transfer, which is ideally suited for studying transport through multiple scattering layers. The model predicts the specular and diffuse reflection and transmission of multilayer composite films, including interface reflections, for diffuse or collimated incidence. For spherical particles in the diffusion approximation, we derive closed-form expressions for the matrix coefficients and show remarkable agreement with numerical Monte Carlo simulations for a range of absorption values and film thicknesses, and for an example multilayer slab.

Optimized design and fabrication of polymer/silica thermo-optic switch with low power-consumption

Donghai Niu, Shiqi Sun, Qiang Xu, Minghui Jiang, Xibin Wang, Zhi-Yong Li, Changming Chen, Yuanda Wu, and Da-Ming Zhang

Doc ID: 295763 Received 10 May 2017; Accepted 18 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: In this paper, the power-consumption characteristics of the polymeric thermo-optic (TO) switch consisting of a silica under-cladding on silicon substrate, a polymer core surrounded with polymer upper-cladding, and the aluminum (Al) heating electrodes with different widths were investigated. Norland Optical Adhesive 73 (NOA 73) with a larger TO coefficient was selected as the core layer, which could reduce the power-consumption effectively. The silica under-cladding with large thermal conductivity could shorten the response time. The influences of the heating electrode width and the air trench structure on the power-consumption of the device were systemically studied. The device with different widths of electrodes was fabricated by using conventional semiconductor fabrication techniques and measured with the planar optical testing system. Under 1550-nm wavelength, the power-consumption of the device would be reduced from .27 mW to 4.35 mW while the heating electrode width was decreased from 25 μm to 7 μm. Furthermore, it would be reduced to 1.7 mW after the air trench structure being employed. The switching time of the device was also measured, which was about 200 μs.

Bessel function expansion to reduce the calculation time and memory usage for cylindrical computer-generated holograms

Yusuke Sando, Daisuke Barada, Jackin Boaz Jessie, and Toyohiko Yatagai

Doc ID: 295010 Received 02 May 2017; Accepted 18 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: This study proposes a method to reduce the calculation time and memory usage required for calculating cylindrical computer-generated holograms. The wavefront on the cylindrical observation surface is represented as a convolution integral in the three-dimensional (3D) Fourier domain. The Fourier transformation of the kernel function involving this convolution integral is analytically performed using a Bessel function expansion. The analytical solution can reduce both the calculation time and the memory usage drastically without any cost compared with the numerical method using fast Fourier transform (FFT) to Fourier transform the kernel function. In this study, we present the analytical derivation, the efficient calculation of Bessel function series, and a numerical simulation. Furthermore, we demonstrate the effectiveness of the analytical solution through comparisons of calculation time and memory usage.

Beam splitter and router via incoherent pump assisted electromagnetically induced blazed grating

Yu-Yuan Chen, Zhuan-Zhuan Liu, and Ren-Gang Wan

Doc ID: 292226 Received 05 Apr 2017; Accepted 18 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: We propose a scheme for beam splitter and beam router via electromagnetically induced blazed grating in a four-level double-Λ system driven by an intensity-modulated coupling field and an incoherent pump field. The blazed grating relies on the incoherent pump process which helps in inducing large refractivity with suppressed absorption or even gain. Consequently, the weak probe beam can be effectively deflected with high diffraction efficiency, and meanwhile its energy is amplified. When using an intensity mask with two symmetric domains in the coupling field, the presented blazed grating provides the possibility of symmetric beam splitter. The diffraction efficiency and diffraction order of the gratings is sensitive to the intensity of coupling field, thus the gratings can function as tunable asymmetric beam splitter or beam router which distributes the probe field into different spatial directions. Therefore, the proposed scheme may have potential applications in optical communication and networking.

Generation of perfect optical vortices using Bessel-Gaussian beam diffracted by curved fork grating

Mahdi Khodadadi Karahroudi, Bahman Parmoon, Mohammadreza Qasemi, abolhasan mobashery, and hossain saghafifar

Doc ID: 292355 Received 07 Apr 2017; Accepted 16 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: Perfect optical vortices (POVs) are beams whose topological charges are independent of radius unlike conventional optical vortices. POVs are Fourier transformation of Bessel-Gaussian (BG) beam and can be seeing in the far-field diffraction of BG beams. In this paper, we present the generation of POVs of arbitrary charge using curved fork grating (CFG) illuminated by BG beam. For this purpose, firstly, a theoretical study of Fresnel-Kirchhoff integral for diffraction of BG beam by CFG is done. The analytical results show the presence of vortex beams with various topological charges in diffraction orders. Then, diffraction of BG beam with the order (l) by CFG with a topological charge (p) is numerically simulated. Additionally, experimental results prove the generation of POVs in diffraction orders. Also, experimental interference patterns obtained by interfering a POV and Gaussian beam confirm the ability of analytical solution to determine the topological charges of vortex beams. Comparison of the results reveals the validity of the analytical, simulation and experimental results.

Frequency domain staring pump-probe technique for Brillouin gain/loss spectrum measurement

Hongwei Li, Ning Chang, Hongying Zhang, Bo Wang, Wei Gao, and Zhihan Zhu

Doc ID: 290955 Received 20 Mar 2017; Accepted 16 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: We propose and demonstrate a modified frequency sweep-free pump-probe technique, called staring pump-probe technique (SPPT) for Brillouin signal measurement based on stimulated Brillouin scattering. The SPPT retains the advantages of conventional pump-probe technique, and employs a simple device and low-cost measurement system. Moreover, the Brillouin gain/loss spectrum (BGS/BLS) can be reconstructed without frequency-sweep thus greatly improves the measurement speed. In this paper, an approximate flat-top spectrum broadened probe light is introduced through distributed feedback laser by direct modulation. The BGS/BLS is reconstructed with the enhanced signal-noise ratio of approximate 21dB/ dB. This technique has a potential application for some Brillouin scattering involved Brillouin frequency shift measurement.

Multiobjective Optimization for Plasmonic Nanoslit Array Sensor using Kriging Models

Kyoung-Youm Kim and Jaehoon Jung

Doc ID: 291162 Received 22 Mar 2017; Accepted 16 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: We propose an efficient multiobjective optimization approach for a plasmonic nanoslit array sensor using Kriging surrogate models. The universal Kriging models whose regression functions are 0th, 1st and 2nd order polynomial are adopted to estimate objective functions. The multiobjective extension of the genetic algorithm is used for Pareto optimal sensor geometry. The objective functions are the figure of merit defined as a ratio of peak wavelength shift at molecular adsorption and 3dB bandwidth of transmission spectrum and peak transmission power, respectively. The optical properties of plasmonic slit sensor are investigated such as transmission power, bandwidth, and peak shift using the finite element method.

Estimating constituents of optical isomers in mixed solution based on spin Hall effect of light

Hang Zhou, Yingjie Wei, Wenjie Hao, and Zhiyou Zhang

Doc ID: 292056 Received 06 Apr 2017; Accepted 16 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: In this paper, an optical method for precisely estimating constituents of optical isomers(OI) in mixed solution is presented. We convert the composition ratio of OI into polarization-rotation-dependent spin Hall effect of light (SHEL). The theoretical model between the SHEL and OI composition ratio is established in the geometrical-optics picture and the spatial shift can be measured through weak measurement technique. Based on our theory, the concentration of glucose and fructose in a mixed solution are separately obtained. Our accurate measurements of the chiral enantiomer composition can provide an avenue for chiral drug synthesis and analysis.

Calibration of night vision goggles:an SI units-based gain measurement

Vyacheslav Podobedov, George Eppeldauer, and Thomas Larason

Doc ID: 290193 Received 06 Mar 2017; Accepted 16 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: A gain measurement technique for the calibration of night vision goggles (NVG) is proposed and evaluated. This technique is based on the radiance measurements at the input and output of the NVG. In contrast to the old definition which uses a non-International System of Units (SI) traceable luminance, the “equivalent luminance unit”, the suggested technique utilizes the radiance quantities that are traceable to the SI units through NIST standards. Due to the implementation of the scaling coefficients originating from the NVG spectral responsivities, the same NVG gain is expected within both techniques. The suggested method was evaluated at the NIST night vision calibration facility and the experimental data were compared to results obtained with a commercial test set. The comparison of the radiometric quantities indicated differences up to 15 % due to different calibration conditions. However, at proper calibration, an equal NVG gain within both suggested and old gain definitions was measured for the goggles with a filmless image tube. The NVG gain uncertainty analysis including the effect of the no-moon night sky radiation was performed for goggle types A, B, and C.

Effect of oxygen partial pressure in deposition ambient on the properties of RF magnetron sputter deposited Gd2O3 thin films

Sk Haque, Rajnarayan De, S Tripathi, Chandrachur Mukherjee, A K Yadav, DIBYENDU BHATTACHARYYA, S Jha, and N. Sahoo

Doc ID: 290507 Received 21 Apr 2017; Accepted 16 Jun 2017; Posted 23 Jun 2017  View: PDF

Abstract: Gadolinium oxide is an excellent optical material which offers high transmission in wide wavelength range of 200 to 1600 nm and exhibits a high refractive index of ~1.80 @ 550 nm. In the present study, a set of Gd2O3 thin films has been deposited on fused silica substrates by rf sputtering of Gd2O3 target under various O2 to Ar flow ratio. The samples have been characterized by grazing incidence X-ray diffraction (GIXRD) to study the long range structural behavior, by grazing incidence X-ray reflectivity (GIXR) to study density and surface roughness of the films, by Atomic Force Microscopy (AFM) measurements to study morphological properties and by transmission spectrophotometry and spectroscopic ellipsometry techniques to study their optical properties. It has been observed that the films deposited with 10% oxygen partial pressure has low density, high surface roughness, high void content which results in a low value of refractive index of this film and film quality improves as oxygen partial pressure is further increased. Extended X-ray Absorption Fine Structure (EXAFS) measurement with synchrotron radiation has also been employed to extract local structural information around Gd sites which has in turn been used to explain some of the observed macroscopic properties of the films.

UV-visible broadband wide-angle polarization-independent absorber based on multiple metal groove structures

Tao Wu, Jianjun Lai, Shaowu Wang, Xiaoping Li, and Ying Huang

Doc ID: 295906 Received 15 May 2017; Accepted 15 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: A new periodic Al groove structure coated by SiO2 thin film is designed and numerically investigated for wide-angle and polarization-independent broadband absorption. A metal groove array presents optical absorption enhancement due to localized surface plasmon resonance with the absorption peak capable to be shifted by the depth control of metal groove. Broadband absorption can be realized by a periodic array of metal grooves with different depths combined in one single period. A two-dimensional Al structure with four different grooves in each period is designed to realize polarization independent broadband absorption from 220 nm to 800 nm with average absorption efficiency over 80% within the incident angle of 40°. These wide-angle and broadband absorption structure can be applied in UV/Visible related biochemical sensor, solar cell or photocatalysis.

High performance Surface-Enhanced Ramanscattering substrate prepared by self-assembling ofAg nanoparticles into the nanogaps of Ag nanoislands

Jiamin Quan, Yong Zhu, Jie Zhang, Junying Li, and Ning Wang

Doc ID: 292689 Received 19 Apr 2017; Accepted 15 Jun 2017; Posted 15 Jun 2017  View: PDF

Abstract: We report an effective and simple method to further enhance the surface-enhanced Raman scattering (SERS) by Agnanoparticles (AgNPs) self-assembling into the nanogaps of an Ag nano-island (AgNIs). The AgNIs prepared bydewetting of Ag film created a nano-rough surface, which induced the Ag nanoparticles to regularly deposit into thenanogaps. AgNPs and AgNIs samples were also prepared for comparative analysis. Their SERS activities wereinvestigated theoretically and experimentally. Experimental enhancement factors (EF) for AgNPs, AgNIs, andAgNPs decorated AgNIs substrate (AgNPs-AgNIs) were ~107, ~106, ~108, respectively, with relative standarddeviation (RSD) of 66.1%, 12.9% and 13.2%. Remarkable enhancement (EF ≈ 108) and excellent reproducibility(RSD = 13.2%) indicated the AgNPs-AgNIs had a high potential in practical application. Electromagnetic simulationusing COMSOL Multiphysics demonstrated that the additional enhancement of the SERS effect could be mainlyattributed to the improvement of local electromagnetic field. Moreover, the deposition process of Ag nanoparticleswas analyzed in detail to understand the reproducibility of AgNPs-AgNIs.

Cooperative execution of auto-focusing metrics indigital lensless holographic microscopy for internalstructuredsamples

Carlos Trujillo and Jorge Garcia-Sucerquia

Doc ID: 295180 Received 03 May 2017; Accepted 15 Jun 2017; Posted 19 Jun 2017  View: PDF

Abstract: The cooperative execution of two metrics to determine automatically the best focal plane in digital lenslessholographic microscopy (DLHM) is presented. Two stages compose this proposal: first, a quick coarse search overthe whole reconstruction range by using Dubois´ metric allows the finding of a range in which the best focal planecan be found. In a second stage, the modified enclosed energy (MEE) metric is used within the found range in theformer stage to finely determine the best focal plane. While this cooperative implementation keeps the proveneffectiveness of the MEE in DLHM, it reduces at least 11-time the total computational complexity of the autofocusingmethod with respect to MEE method only. This proposal has been validated experimentally with DLHMholograms of a paramecium specimen, a polystyrene beads and the section of the head of a DrosophilaMelanogaster fly.

Performance analysis of zinc oxide implemented lossy mode resonance based optical fiber refractive index sensor utilizing thin film/nanostructure

Sruthi Usha and Banshi Gupta

Doc ID: 292330 Received 12 Apr 2017; Accepted 14 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: A detailed primeval study on the LMR behaviour of zinc oxide (ZnO) coated optical fiber as a refractive index sensor is carried out. Theoretical evaluation predicts ZnO as a good choice for the LMR based chemical and gas sensor operating in visible region of electromagnetic spectrum. To confirm, optical fiber probe is fabricated with optimized film thickness of ZnO over unclad core of the fiber and characterized. Additionally, LMR based nanosensor platform utilizing ZnO has also been investigated to find the compatibility of nanotechnological LMR sensor. The nanostructured LMR sensors have shown enhanced sensitivity in comparison to bulk layered probe.

Broadening the reflection bandwidth of polymer-stabilized cholesteric liquid crystal via a reactive surface coating layer

Jongyoon Kim, Hyungmin Kim, Seongil Kim, suseok choi, Wonbong Jang, Jinwuk Kim, and Ji-Hoon Lee

Doc ID: 290313 Received 08 Mar 2017; Accepted 14 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: We report a method of broadening the reflection bandwidth of polymer-stabilized cholesteric liquid crystal (PSCLC). The top substrate was consecutively coated with a polyimide (PI) and a reactive mesogen (RM) layer, while the bottom substrate was coated with only PI. We exposed the top substrate with the RM coating to UV light. The reflection bandwidth of the PSCLC samples where the top substrate was over-coated with RM was significantly broader than the samples where both substrates were coated with PI. In addition to the effect of the UV intensity gradient, the RM-coated top substrate has a chemical affinity to bulk RM, promoting formation of the pitch gradient and broadening the reflection bandwidth in the sample.

Full-color holographic 3D display using slice-based fractional Fourier transform combined with free-space Fresnel diffraction

Zhen Zhang, Siqing Chen, Huadong Zheng, Zhenxiang Zeng, Hongyue Gao, yu yingjie, and Anand Asundi

Doc ID: 291106 Received 22 Mar 2017; Accepted 14 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: The fractional Fourier transform (FRT) has already been used for computing holograms in holographic display due to its continuity of describing wave diffraction in near field and far field. In this study we propose a method to realize full-color holographic 3D display with combined use of the FRT and the free-space Fresnel diffraction. Slice-based optical configuration and calculation algorithm of FRT are proposed for generating phase-only holograms of full-color 3D objects. Sequential phase-only holograms are generated for reducing the speckle noise of reconstructed images by time-averaging effect. Free-space Fresnel diffraction is used for 3D image reconstruction from the generated holograms. The relationship between the fractional order of different color channel and the free-space Fresnel diffraction distance is analyzed. Chromatic aberrations caused by different wavelengths of RGB lasers are also compensated. Full-color holographic display system using reflective phase-only spatial light modulator (SLM) is established. Both numerical and optical reconstruction results demonstrate the feasibility of the proposed method.

Dynamical range and stability enhancement in electrically fused microknot optical resonators

Alexandra Logvinova, Gal Gottlieb, shir shahal, Moti Fridman, and Yoav Linzon

Doc ID: 291376 Received 27 Mar 2017; Accepted 14 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: Microknot resonators, locally fused using a two-probe technique, have exhibited significantly improvedoptical performance and mechanical stability. They have been operated with low losses both in-situ andas transferred devices. We found consistently more than threefold dynamical range enhancement, whichremained stable in time, in electrically fused MKRs. These devices can be harbored in next generation opticalsensors, actuators, and opto-mechanical applications incorporating MKR-assisted micro-structures,taking advantage of this simple and robust fusing technique.

Micro-mirrors with controlled amplitude and phase

Julien Lumeau, Cihan Koc, and Thomas Begou

Doc ID: 291669 Received 24 Apr 2017; Accepted 14 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: This paper describes the fabrication of circular micro-mirrors with diameters between 50 and 150 µm with controlled amplitude and phase. Design, manufacturing and characterization method are presented.

Sinusoidal phase-modulating laser diodeinterferometer for wide range displacementmeasurement

Ming Zhang, Chang NI, zhu yu, hu chuxiong, Jinchun Hu, Leijie Wang, and Siqi Ding

Doc ID: 291601 Received 04 Apr 2017; Accepted 13 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: A sinusoidal phase-modulating laser diode interferometer for wide range displacement measurement is proposed.To realize wide range displacement measurement, a signal processing method utilizing look-up table to estimatethe dynamic value of the effective sinusoidal phase-modulating depth is detailed, and the error caused by theresidual amplitude modulation and the effective sinusoidal phase-modulating depth in wide range displacementmeasurement can be eliminated. It is discussed that the extended measurement range depends on the monotoneintervals of several specific functions. The simulation and experimental results prove that the sinusoidal phasemodulatinglaser diode interferometer with the proposed method could realize centimeter level displacementmeasurement range.

Inscription of type I and depressed cladding waveguides in lithium niobate using a femtosecond laser

Saurabh Bhardwaj, Kshitij Mittholiya, Anuj Bhatnagar, Rodney Bernard, Jayashree Dharmadhikari, Deepak Mathur, and Aditya Dharmadhikari

Doc ID: 292690 Received 12 Apr 2017; Accepted 13 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: We describe two types of waveguides (type I and depressed cladding) inscribed in lithium niobate using a variable repetition rate (200 kHz-25 MHz), 270 fs duration fibre laser. The type I modification based waveguides have propagation losses in the range from 1.2 to 10 dB/cm at 1550 nm depending on experimental parameters. These waveguides are not permanent; they deteriorate over time. Such deterioration of waveguides can be slowed down from 30 days to 100 days by pre-annealing the samples and by writing at 720 kHz laser repetition rate. The propagation losses measured at 1550 nm show significant improvement for pre-annealed samples. The depressed cladding inscribed waveguides are permanent but the propagation loss depends on the number of damage tracks. A track separation of ~1 µm between adjacent damage tracks yields the lowest propagation loss of 0.5 dB/cm at 1550 nm for a 40 µm diameter waveguide. We observe multimode guidance for sizes in the range 20-80 µm in these waveguide structures at 1550 nm. Their crystalline nature is found to remain intact as inferred from second harmonic generation within the waveguide region. © 2015 Optical Society of America

Light trapping for photovoltaic cells using polarization-insensitive angle-selective filters under monochromatic illumination

Yasuhiko Takeda, Hideo Iizuka, noboru yamada, and Tadashi Ito

Doc ID: 293330 Received 24 Apr 2017; Accepted 12 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: We have proposed a light-trapping concept for photovoltaic (PV) cells under monochromatic illumination with restricted incident angles. We employed a configuration consisting of a shortpass filter (SPF) on the front surface and a diffuse reflector on the rear surface of the cell. The SPF was designed so that it functioned as a polarization-insensitive angle-selective filter. We fabricated 30−80 μm-thick crystalline silicon samples for incident angles changing within 30º, and analyzed the measured results using a ray-trace simulation with the Monte-Carlo method. The ratio of the absorbed intensity to the 1064 nm illumination intensity were 0.69−0.85, which were higher than those equipped with anti-reflection coatings instead of the SPFs by 0.19−0.13. Thus, we have proven the light-trapping concept of the SPF/diffuse reflector configuration for monochromatic illumination. The PV cells could be applied to wireless power supply, in particular from solar-pumped lasers.

Experimental optimization of concatenated tapersMach-Zehnder interferometers operating in the 1000-1150nm wavelength range.

Daniel Toral-Acosta, Alejandro Martínez-Rios, Guillermo Salceda-Delgado, Romeo Selvas-Aguilar, and Víctor Durán Ramírez

Doc ID: 292468 Received 19 Apr 2017; Accepted 12 Jun 2017; Posted 13 Jun 2017  View: PDF

Abstract: Experimental optimization of all fiber Mach-Zehnder interferometers based on concatenated tapers is presented.The experimental optimization was realized by the application of the 4-parameters Taguchi algorithm and the insertion loss of comb filters operating around the 1064 nm wavelength was taken as the parameter to be optimized. The out of band losses were reduced from around 2.5 dB (43.7%) to a minimum of 0.45 dB (9.84%) in one case, and from 2.9 dB (48.71%) to 0.4 dB (8.79%), by using a fixed geometry for the tapers pair, i.e., 1-1-1 mmof up-taper length-waist length-down taper length, and a waist diameter of 40 ❍m.

How good is your lens? Assessing performance with MTF full-field displays

Brandon Dube, Roger Cicala, Aaron Closz, and Jannick Rolland

Doc ID: 292255 Received 10 Apr 2017; Accepted 12 Jun 2017; Posted 14 Jun 2017  View: PDF

Abstract: Modern optical systems achieve incredible resolution and require more thorough testing. We outline a method of measuring the performance of camera lenses across the entire rectangular field of view and presenting the results. Critically, these measurements allow the characterization of misaligned systems with much higher accuracy than typical three or five field point MTF measurements. Examples are provided of both well centered and poorly centered systems.

A Numerical Method Based on Transfer Function for Eliminating Water Vapor Noise from Terahertz Spectra

Yu Huang, Sun Ping, Zheng Zhang, and Chen Jin

Doc ID: 290759 Received 15 Mar 2017; Accepted 11 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: Water vapor noise in the air affects the accuracy of optical parameters extracted from terahertz (THz) time-domain spectroscopy. In this paper a numerical method was proposed to eliminate water vapor noise from the terahertz spectra. According to the Van Vleck-Weisskopf function and the linear absorption spectrum of water molecules in the HITRAN database, we simulated the water vapor absorption spectrum and real refractive index spectrum with a particular line width. The continuum effect of water vapor molecules was also considered. Theoretical transfer function of a different humidity was constructed through the theoretical calculation of the water vapor absorption coefficient and the real refractive index. The THz signal of the Lacidipine sample containing water vapor background noise in the continuous frequency domain of 0.5-1.8 THz was denoised by use of the method. The results show that the optical parameters extracted from the denoised signal are closer to the optical parameters in the dry nitrogen environment.

DBPSK and DQPSK Crosstalk in Single Span WDMSystems Using DRA

Emadeldeen Morsy, Heba Fayed, Ahmed Abd El Aziz, and Mostafa Hussein Aly

Doc ID: 292946 Received 17 Apr 2017; Accepted 10 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: A closed loop formula is derived for the nonlinear crosstalk degradation due to self-phase modulation(SPM) and cross-phase modulation (XPM) in wavelength division multiplexing (WDM) system. Thecrosstalk is investigated in binary phase shift keying (DBPSK) and differential quadrature phase shiftkeying (DQPSK) schemes. The system under consideration is standard single mode fiber (SSMF) withsingle span distributed Raman amplifier (DRA). The backward DBPSK shows a better performance withminimum crosstalk performance of 71% as compared to backward DQPSK.

Six channels multi-wavelength polarization Ramanlidar for aerosol and water vapor profiling

Jiandong Mao, Zhaofei Wang, Juan Li, Hu Zhao, Chunyan Zhou, and Hongjiang Sheng

Doc ID: 284327 Received 17 Jan 2017; Accepted 10 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: Aerosols and water vapor are important atmospheric components, and have significant effects on both atmospheric energyconversion and climate formation. They play the important roles in balancing the radiation budget between the atmosphere andEarth, while water vapor also directly affects rainfall and other weather processes. To further research into atmospheric aerosoloptical properties and water vapor content, a all-time six channels multi-wavelength polarization Raman lidar has been developed inBeifang University of Nationalities. In addition to 1064, 532 and 355 nm Mie scattering channels, the lidar has a polarization channelfor 532nm return signals, a 660nm water vapor channel and a 607nm nitrogen detection channel. Experiments verified the lidar’sfeasibility and return signals from six channels were detected, Using inversion algorithms, extinction coefficient profiles at 1064, 532and 355 nm, Ångström exponent profiles, depolarization ratio profiles, and water vapor mixing ratio profiles were all obtained. Thepolarization characteristics and water vapor content of cirrus clouds, the polarization characteristics of dusty weather, and the watervapor profiles over for different days were also analyzed. Results show that the lidar has the full-time detection capability foratmospheric aerosol optical properties and water vapor profiles, and real-time measurements of aerosols and water vapor over theYinchuan area were realized, providing important information for studying the environmental quality and climate change in thisarea.

Relationship between foot eversion andthermographic foot skin temperature after running

Jose Ignacio Priego Quesada, Marina Gil-Calvo, Irene Jimenez-Perez, Ángel G. Lucas-Cuevas, and Pedro Pérez-Soriano

Doc ID: 290357 Received 09 Mar 2017; Accepted 09 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: The main instruments to assess foot eversion have some limitations (especially for field applications) and therefore it is necessary to explore new methods. The objective was to determine the relationship between foot eversion, using motion analysis, and skin temperature asymmetry of the foot sole (difference between medial and lateral side), using infrared thermography. Twenty two runners performed a running test lasting 30 minutes. Skin temperature of the feet sole was measured by infrared thermography before and after running. Foot eversion during running was measured by kinematic analysis. The weak correlations observed between the variables analysed suggest that skin temperature is not a good predictor of foot eversion. However, these results open interesting future lines of research.

Frequency domain approach to the steady state and stability analysis of dual injection-locked optoelectronic oscillators

Sajad Jahanbakht

Doc ID: 295019 Received 02 May 2017; Accepted 09 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: A frequency domain algorithm is proposed for deriving all of the possible steady state modes of dual injection locked optoelectronic oscillators (DIL-OEOs) corresponding to the detailed system parameters such as the fiber lengths, small signal open loop gains, RF filters’ bandwidths, phase shifting values and injection parameters. It is shown that some or all of the modes computed by the new approach may be unstable; these are just mathematical solutions of the steady state equations. Therefore it is necessary to check the stability of these modes. A stability analysis approach is proposed which is based on simulating the slowly-varying time domain dynamic governing the perturbation variables. The steady state and stability analysis approaches enable one to predict the required injection parameters for having a reliable steady state injection-locked mode in the DIL-OEO system. The new method requires a much smaller runtime compared to the corresponding time-domain methods. In addition it avoids many simplifying assumptions of the corresponding frequency domain approaches presented in the literature. The validities of the steady state and stability analysis methods are verified by comparing their results with full time domain integrations and with other predictions regarding the required injection parameters for phase locking, presented in the literature.

Freeform optical design for a non-scanning corneal imaging system with a convexly curved image

Yunfeng Nie, Herbert Gross, Yi Zhong, and Fabian Duerr

Doc ID: 295489 Received 10 May 2017; Accepted 09 Jun 2017; Posted 12 Jun 2017  View: PDF

Abstract: Most existing techniques that are typically used by specialists to image the cornea are based on point-, slit- or annular- scanning due to a narrow field of view. The difficulty to achieve a larger field of view comes from the convex shape of human eyeball. Field curvature for a refractive imaging system with positive power is typically negative, thus a concave image surface. In order to view the full cornea and sclera with snapshot imaging, we calculate qualified two- and three-mirror solutions from Seidel aberration theory. A three-mirror solution is further optimized as a high-resolution off-axis imaging system using freeform surfaces, which can obtain a full-field tailored image shell without scanning. The lateral resolution on the cornea is about 10μm with good MTF and spot performance. To ease the assembly of three mirrors, a monolithic design is achieved with slightly lower resolution, leading to a potential mass production solution.

Reflectionless compact nonmagnetic optical waveguide coupler design based on transformation optics

Mohammad Saeed Majedi, Hossein Eskandari, and Amir Reza Attari

Doc ID: 291248 Received 23 Mar 2017; Accepted 09 Jun 2017; Posted 09 Jun 2017  View: PDF

Abstract: The design of an optical waveguide coupler has several challenges, such as reflection losses at the interfacesof the coupler, material complexity for optical applications and the coupling between arbitrarymaterials at the input and the output of the coupler. In this paper, for the first time to the best of ourknowledge, we propose a solution to overcome the above difficulties. For this purpose, we introduce anauxiliary transformation function and an impedance scaling function. The auxiliary function specifiesthe matched dielectric materials at the input and output interfaces of the coupler, and the scaling functionsuppresses the reflections and makes the material non-magnetic for TM polarization. As a result, anoptical waveguide coupler is designed that can ideally couple two waveguides with arbitrary dielectricmaterials and arbitrary cross-sections using a non-magnetic material. Validation of the design method isdone by using COMSOL Multiphysics.

Numerical reproduction and explanation of road surface mirages under grazing-angle scattering

Jia Lu and Huaichun Zhou

Doc ID: 292391 Received 10 Apr 2017; Accepted 08 Jun 2017; Posted 09 Jun 2017  View: PDF

Abstract: The mirror-like reflection image of the road surface under grazing-angle scattering can be easily observed in daily life. It was suggested that road surface mirages may occur due to a light-enhancing effect of the rough surface under grazing-angle scattering. The main purpose of this work is to explain the light-enhancing mechanism of rough surfaces under grazing-angle scattering. The off-specular reflection from a random rough magnesium oxide ceramic surface is analyzed by using the geometric optics approximation method. Then, the geometric optics approximation method is employed to develop a theoretical model to predict the observation effect of the grazing-angle scattering phenomena of the road surface. The rough surface is assumed to consist of small-scale rough surface facets. The road surface mirage is reproduced from a large number of small-scale rough surface facets within the eye’s resolution limit at grazing scattering angles as the average BRDF value at the bright location is about twice that of the surface in front of the mirage. It is suggested that the light-enhancing effect of the rough surface under grazing-angle scattering is not proper to be termed as “off-specular reflection”, since it has nothing to do with the “specular” direction, with respect to the incident direction.

Numerical investigation of nonlinear shrinkage effectsin volume holographic gratings

Shuhei Yoshida and Shuma Horiuchi

Doc ID: 292656 Received 13 Apr 2017; Accepted 08 Jun 2017; Posted 09 Jun 2017  View: PDF

Abstract: Photopolymers are widely used as a recording medium in holographic data storages but they shrinkduring polymerization. We proposed a nonlinear shrinkage model to numerically evaluate the effect ofphotopolymer shrinkage on signal quality. Specifically, we developed both a numerical model in whichthe shrinkage factor is determined locally according to the light intensity, and a numerical simulationmethod that can handle computational lattices distorted by shrinkage. We clarified the influence ofshrinkage on diffraction efficiency, angle selectivity, wavelength selectivity, signal-to-noise ratio, andsymbol error rate. This study provides useful information for system design of holographic data storage.

Radiometric imaging by double exposure and gain calibration

Iftach Klapp, Sahar Papini, and Nir Sochen

Doc ID: 291020 Received 22 Mar 2017; Accepted 07 Jun 2017; Posted 08 Jun 2017  View: PDF

Abstract: Due to low cost and small size, uncooled microbolometer-based thermal focal plane arrays (UC-FPAs) are veryattractive for radiometry. However, being non-cooled, they suffer from temporally and spatially dependentchanges that require constant calibration. While the gain calibration can be reasonably realized by two-pointcorrection, the offset due to internal radiation loads poses a complicated calibration scheme. We present a newcomputational optics approach that simplifies the essential calibration for temperature offset. Using twosuccessive images of the object taken with different known blur levels, one can eliminate the object term from theimage-formation equation, resulting in an equation for the unknown sensor offset. A general algebraic model ispresented for the space-variant case followed by solutions using both direct inverse method and iterative solver.The new scheme allows restoration of the radiometric value within 1% error with the direct method, 0.2% errorwith the iterative scheme. Account of the influence of realistic lens positioning error on restoration accuracy wasgiven. Results using direct inverse methods for restoring the radiometric values yield restoration error with a goodaverage error of 3.7% and less.

Model of material removal function and experimentalstudy in a novel magnetorheological finishing processusing small ball-end permanent-magnet polishinghead

chen mingjun, Henan Liu, Jian Cheng, Bo Yu, and Zhen Fang

Doc ID: 291532 Received 12 Apr 2017; Accepted 07 Jun 2017; Posted 08 Jun 2017  View: PDF

Abstract: In order to achieve the deterministic finishing of optical components with concave surfaces of curvature radiuswithin 10mm, a novel magnetorheological finishing (MRF) process using small ball-end permanent-magnetpolishing head with diameter of 4mm is introduced. The characteristics of material removal in the proposed MRFprocess are studied. The model of material removal function for the proposed MRF process is established based onthe three-dimensional hydrodynamics analysis and Preston’s equation. The shear stress on the workpiece surfaceis calculated by means of resolving the presented mathematical model using numerical solution method andanalysis result reveals that the material removal in the proposed MRF process shows a positive dependence onshear stress. And experimental researches are conducted to investigate the effect of processing parameters onmaterial removal rate and improve the surface accuracy of a typical rotational symmetrical optical component. Theexperimental results show that the surface accuracy of finished component of K9 glass material has been improvedto 0.14μm (PV) from the initial 0.8μm (PV) and the finished surface roughness Ra is 0.0024μm. It indicates that theproposed MRF process can be used to achieve the deterministic removal of surface material and perform thenanofinishing of small curvature radius concave surfaces.

Comparison of symmetric and asymmetric doublequantum well extended cavity diode lasers forbroadband passive mode-locking at 780 nm

Heike Christopher, Evgeny Kovalchuk, Hans Wenzel, Frank Bugge, Markus Weyers, Andreas Wicht, Achim Peters, and Guenther Traenkle

Doc ID: 292128 Received 19 Apr 2017; Accepted 07 Jun 2017; Posted 08 Jun 2017  View: PDF

Abstract: We present a compact, mode-locked diode laser system designed to emit a frequency comb in the wavelength range around 780 nm. We compare the mode-locking performance of symmetric and asymmetric double quantum well ridge-waveguide diode laser chips in an extended-cavity diode laser configuration. By reverse biasing a short section of the diode laser chip passive mode-locking at 3.4 GHz is achieved. Employing an asymmetric double quantum well allows for generation of a mode-locked optical spectrum spanning more than 15 nm (full width at -20 dB) while the symmetric double quantum well device only provides a bandwidth of ~ 2.7 nm (full width at -20 dB). Analysis of the RF noise characteristics of the pulse repetition rate shows a RF linewidth of about 7 kHz (full width at half maximum) and of at most 540 Hz (full width at half maximum) for the asymmetric and symmetric double quantum well device, respectively. Investigation of the frequency noise power spectral density at the pulse repetition rate shows a white noise floor of approx. 2100 Hz²/Hz and of at most 170 Hz²/Hz for the diode laser employing the asymmetric and symmetric double quantum well structure, respectively. The pulse width is less than 10 ps for both devices.

Design of a Collimated UV-LED Exposure Unit Based on Light Spread Function Method

Shin Hong Kuo and Chi-Feng Chen

Doc ID: 280501 Received 22 Dec 2016; Accepted 06 Jun 2017; Posted 06 Jun 2017  View: PDF

Abstract: A collimated and uniform UV-LED exposure unit (EU) applied in a printed circuit board is investigated by the light spread function (LSF) method. To accurately calculate the source-to-source distance of collimated UV-LED sources and achieve uniform irradiance in the exposure area, we propose a regional maximally flat condition for the LSF. This regional maximally flat condition contains irradiance information from multiple positions in two dimensions. To verify the design results, we built this parameter into optical simulation software (OSS) and used it in our LSF method calculations. The obtained collimated UV-LED EU results show uniformity and average irradiance values of 98. % and 43.32 mW/cm2, respectively. Thus, we can conclude that the proposed LSF method is effective for achieving a uniform irradiance distribution.

Nonlinear Photonics On-a-Chip in III-V Semiconductors:Quest for Promising Material Candidates

Shayan Saeidi, Kashif Awan, Lilian Sirbu, and Ksenia Dolgaleva

Doc ID: 287371 Received 23 Feb 2017; Accepted 06 Jun 2017; Posted 06 Jun 2017  View: PDF

Abstract: We propose several designs of nonlinear optical waveguides based on quaternary III-V semiconductorsAlGaAsSb and InGaAsP. These semiconductor materials have been widely used for laser sources. Theirnonlinear optical properties, however, yet remain unexplored, while the materials definitely hold promisefor nonlinear photonics on-a-chip. The latter argument is based on the fact that III-V compounds tendto exhibit high values of the nonlinear optical susceptibilities, while the nonlinear absorption in thesematerials can be minimized in the wavelength range of interest through a proper selection of the materialcomposition. We present the modal analysis for the designed waveguide structures and show that the effectivemode area much less than 1mm2 can be achieved through a design optimization in each of the twocompounds. We also present specific waveguide designs that demonstrate zero dispersion at the wavelengthsof interest. The designed AlGaAsSb and InGaAsP waveguides are thus expected to demonstratehigh values of the nonlinear coefficient and efficient nonlinear optical interactions.

High Conversion-Efficiency All-Optical Wavelength Converter Based on Cascaded Highly Nonlinear Fibers

Jiaqin Qian, Bowen Chen, Chen Wei, and Mingyi Gao

Doc ID: 295186 Received 03 May 2017; Accepted 06 Jun 2017; Posted 07 Jun 2017  View: PDF

Abstract: All-optical wavelength converters based on parametric processing of highly nonlinear fiber (HNLF) can providelow energy consumption, fast process speed and modulation format agnosticism. A longer HNLF with largernonlinear coefficient and high pump power will contribute to achieve higher conversion efficiency. However, theinjected pump power to the fiber is limited by its Stimulated Brillouin Scattering (SBS) threshold, where longerfibers always have lower threshold powers. In the paper, we proposed an all-optical wavelength converter withhigher conversion efficiency by cascading two different HNLFs. We experimentally achieved -8-dB conversionefficiency and good converted signals with negligible power penalties.

Deconvolution of spectral power distribution of highpowerlaser diode arrays

Bongtae Han, Dae-Suk Kim, and Ou Zhang

Doc ID: 290805 Received 22 Mar 2017; Accepted 06 Jun 2017; Posted 08 Jun 2017  View: PDF

Abstract: A novel method is proposed to predict the spectral power distributions (SPDs) of individual emitters in a highpower laser diode (LD) array. The proposed method deconvolutes the SPD of an LD array by taking into accountthe thermal crosstalk effect as well as the current competition effect. A complete analytical expression todeconvolute the SPD of an LD array is described. The expression contains four key parameters that are to bemeasured experimentally: (1) the normalized SPD of the central emitter, (2) the temperature coefficient ofwavelength, (3) the current competition constant, and (4) the maximum power of the center emitter. The methodis implemented with a commercial water-cooled high power LD array. The SPDs of the LD array predicted from theSPDs of individual emitters are compared with the experimentally measured SPD of the LD array. The results showan excellent agreement in both shape and magnitude, which corroborates the validity of the proposed method.

Guided Lock of a Suspended Optical Cavity Enhanced by a Higher Order Extrapolation

Kiwamu Izumi, Koji Arai, Daisuke Tatsumi, Ryutaro Takahashi, Osamu Miyakawa, and Masa-Katsu Fujimoto

Doc ID: 292098 Received 05 Apr 2017; Accepted 05 Jun 2017; Posted 06 Jun 2017  View: PDF

Abstract: Lock acquisition of a suspended optical cavity can be a highly stochastic process and is therefore nontrivial.Guided lock is a method to make lock acquisition less stochastic by decelerating the motion of the cavity length based on an extrapolation of the motion from an instantaneous velocity measurement.We propose an improved scheme which is less susceptible to seismic disturbances by incorporating the acceleration as a higher order correction in the extrapolation. We implemented the new scheme in a 300-m suspended Fabry-Perot cavity and improved the success rate of lock acquisition by a factor of 30.

A Method to Calculate Laser Rader Cross-Section of rotationally symmetric targets

Yanhui Li, yongzhi du, Lu Bai, Zhen-Sen Wu, Haiying Li, and Yun-hua Cao

Doc ID: 287847 Received 08 Mar 2017; Accepted 05 Jun 2017; Posted 06 Jun 2017  View: PDF

Abstract: Laser radar cross-section (LRCS) is an important parameter in the study of target scattering characteristics. In this paper, a method to calculate LRCS of rotationally symmetric targets is presented which based on the generatrix, rotation axis, incident and scattering direction. Monostatic LRCS of the four kinds of rotationally symmetric targets (cone, rotating-ellipsoid, super-ellipsoid and blunt-cone) is calculated at the wavelength of 1.06μm. Compared with the results of triangular patch method, it verify the correctness of the introduced method. The method does not need the geometric modeling and reduces the complexity of algorithm, which is advantages over triangular patch method. This work provides an idea for the calculation of LRCS of complex full-size target.

Amendment performance of apodized TFBG for quasi-distributed-based sensor

Eman Elzahaby, ishac Kandas, and Mostafa Hussein Aly

Doc ID: 293274 Received 24 Apr 2017; Accepted 05 Jun 2017; Posted 05 Jun 2017  View: PDF

Abstract: In this work, the characteristics of reflectivity spectra produced inside reflective-tilted fiber Bragg grating (R-TFBG) are investigated, seeking a remarkable performance that could be able to upgrade the sensitivity range for temperature-strain sensors of quasi-distribution type. We introduce an optimized performance through a comparative investigation between different evaluations parameters together, such as core radius, tilt angle, and elite selection of apodization profiles, in addition to the traditional parameters such as grating length, L, and index modulation amplitude, ∆n. Regarding the tilt angle, its increase affects the full width at half maximum (FWHM) affirmatively, while having a negative impact on the maximum reflectivity. By controlling L and Δn, a compromised solution is achieved to retrieve the maximum reflectivity to be around 1.0. Regarding the sidelobes, the Kaiser profile is the best candidate that minimized main sidelobe level (MSL) and raised sidelobes suppression ration (SLSR) at any tilt angle, while tanh apodization is the best choice from prospective of raising the ramp down sidelobes asymptotic decay (AD). The contrasts in the optimization process are examined through investigating the R-TFBG quasi-distributed sensors to be applied to a temperature-strain sensing system. The objective is to evaluate an assessment for the performance of sensor system, that extents the range and efficiency of temperature-strain ranges. Based on our analysis, the sensitivity range is upgraded for temperature change to reach 179 °C and for strain to be 3000 με at a tilt angle of 10° with FWHM of 0.063 nm, attenuation of - 154 dB for MSL of 75.5 % and SLSR of - 60 dB/nm.

Hybrid plasmonic mode converter - Theoreticalformulation and design with a graphical approach

Yin-Jung Chang and Ren-Wei Feng

Doc ID: 294964 Received 01 May 2017; Accepted 05 Jun 2017; Posted 05 Jun 2017  View: PDF

Abstract: The theoretical formulation based on rigorous transmission-line networks is developed for a generalmode conversion problem and lays the groundwork for a simpler yet more efficient graphical designapproach for hybrid plasmonic mode converters (HPMCs). The concurrence of co- and cross-polarizationconversion to and among higher-order photonic and HP modes followed by subsequent powerredistributions and losses over the course of the HPMC can lead to performance degradation andlargely determines the silicon core thickness. Using gradient ascent of the TM polarization fractionincorporated with modal index contours sets critical perturbation parameters for required transversestructural asymmetry. Polarization reversal estimates are shown to be practically applicable for about 60%of the total device length. The mode conversion efficiency (MCE), insertion loss (IL), and the polarizationconversion efficiency of the proposed HPMC (< 7 × 0.4 μm2) at λ0 = 1550 nm are 90.04%, 0.4691 dB, and99.96%, respectively. The 85%-bandwidth of the MCE is 135 nm while the IL stays below 0.5 dB over a68-nm spectral range.

Temperature sensing through long period fiber gratings mechanically induced on tapered optical fibers

Maria Pulido-Navarro, Ponciano Escamilla-Ambrosio, Sigifredo Marrujo_García, Jose Alvarez-Chavez, and Fernando Martínez-Piñòn

Doc ID: 290496 Received 14 Mar 2017; Accepted 03 Jun 2017; Posted 06 Jun 2017  View: PDF

Abstract: In this work the feasibility of employing two well-known techniques already used on designing optical fiber sensors is explored. The first technique employed is single mode optical tapers which were fabricated using a taper machine designed, built and implemented in our laboratory. This implementation highly reduced the costs and fabrication time allowing us to produce the desired taper length and transmission conditions. The second technique employed is fiber Bragg gratings which we decided to have them mechanically induced and for that reason we devised and produced our own gratings with the help of a computer numerical control tool. This grating had to be fabricated with aluminum in order to withstand temperatures up to 600 0C. When light traveling through an optical fiber reaches a taper it couples into the cladding layer and comes back into the core when the taper ends. In the same manner when the light encounters gratings in the fiber it couples to the cladding modes, when the gratings ends, the light couples back into the core. For our experimentation the tapering machine was programed to fabricate single mode tapers with 3cm length and the mechanically induced gratings characteristics were 5cm length, period 500 µm and depth of the period 300 µm. For the conducting tests the tapered fiber is positioned in between two aluminum slabs, one grooved and the other plane. These two blocks accomplish the mechanical induced LPG; the gratings on the grooved plaque are imprinted on the taper forming the period gratings. An optical spectrum analyzer is used to observe the changes on the transmission spectrum as temperature varies from 20 up to 600 0C. The resultant attenuation peak wavelength in the transmission spectrum shifts up to 8 nm which is a higher shift compared to what has been reported using non tapered fibers. As the temperature gets higher there is no longer a shift but there is significant power loss. Such characteristic can be used as well for sensing applications.

Symmetry Evaluation for IFOG Coil Utilizing Bidirectional Distributed Polarization Measurement System

Feng Peng, Chuang Li, Jun Yang, Chengcheng Hou, Haoliang Zhang, Zhangjun Yu, yuan yonggui, Hanyang Li, and Libo Yuan

Doc ID: 286005 Received 01 Feb 2017; Accepted 30 May 2017; Posted 31 May 2017  View: PDF

Abstract: We propose a dual-channel measurement system for evaluating the optical path symmetry of an interferometric fiber optic gyro (IFOG) coil. Utilizing the bidirectional distributed polarization measurement system, the forward and backward transmission performances of an IFOG coil are characterized simultaneously by just one-time measurement. The simple but practical configuration is composed of a bidirectional Mach-Zehnder interferometer and the multi-channel transmission devices connected to the IFOG coil under test. The static and dynamic temperature results of the IFOG coil reveal that its polarization-related symmetric properties can be effectively obtained with high accuracy. The optical path symmetry investigation is highly beneficial in monitoring and improving the winding technology of IFOG coil, and reducing the nonreciprocal effect of IFOG.

Evaluation of adaptively enhanced two-shot fringe pattern phase and amplitude demodulation methods

Dominika Saide, Maciej Trusiak, and Krzysztof Patorski

Doc ID: 290799 Received 23 Mar 2017; Accepted 28 May 2017; Posted 30 May 2017  View: PDF

Abstract: Phase-shifting interferometry is a standard tool in optical metrology. Most frequently it needs three or more interferograms to solve the system of fringe equations for phase or amplitude retrieval which limits its time resolution. Recently the topic of two-shot arbitrary-phase-step fringe pattern phase and amplitude demodulation is flourishing and attracting attention with several novel and interesting methods being proposed. In this contribution we evaluate six up-to-date two-shot phase-shifting methods analysing their main error sources and proposing efficient ways to minimize their influence by adaptive filtering using the Hilbert-Huang transform.

Beam modulation due to thermal deformation of grating in spectral beam combining system

Linxin Li, jin yunxia, Fanyu Kong, leilei wang, Junming Chen, and jianda Shao

Doc ID: 290570 Received 23 Mar 2017; Accepted 23 May 2017; Posted 24 May 2017  View: PDF

Abstract: As the combined power of a spectral beam combining (SBC) system increases, temperature of the multilayerdielectric grating (MDG) inevitably rises, under the influence of high-power continuous-wave (CW) laserirradiation. Hence, thermal deformation of the MDG occurs, along with degeneration of the combined beamproperties. In this study, we experimentally and theoretically investigate the influence of the MDG thermaldeformation on the combined beam properties. An experimental setup is first proposed, in which beam quality M2,beam profile, MDG wave-font deformation are investigated. The experimental results indicate that the beamquality clearly degrades and the MDG wave-front deformation becomes more significant with increasing pump-CWpower density. On this basis, a calculation model for MDG thermal deformation in SBC systems is proposed. Theresults indicate that MDG wave-front deformation becomes more significant, combined beam profile deformed andbeam quality of the combined beam degrades with increasing power density. Further, thermal expansion of thesubstrate is a crucial factor that induces MDG wave-front deformation and far-field intensity modulation.

Monitoring stress changes in carbon fiber reinforced polymer composites with GHz radiation

Peter Schemmel and Andrew Moore

Doc ID: 292340 Received 12 Apr 2017; Accepted 16 May 2017; Posted 17 May 2017  View: PDF

Abstract: We performed proof of principle experiments to demonstrate that the reflected power of GHz illumination from the surface of carbon fiber reinforced polymer (CFRP) composites is linearly related to the stress in the material. We introduce a stress coefficient to describe the change in normalized power with applied stress, because the effect is attributed partially to changes in the refractive index of the effective medium comprising the carbon fibers in the polymer matrix. The stress coefficient was -0.549 ± 0.134 /GPa for 3 mm thick samples, and -0.154 ± 0.024 /GPa for 1 mm thick samples, both linear up to the measurement limits of 40 MPa and 100 MPA respectively. This technique opens up the possibility of non-destructive evaluation of stresses in CFRP components for quality assurance in manufacturing settings as well as structural health monitoring of in-service aerospace and automotive parts.

Intrinsic Decomposition From A Single Spectral Image

Xi Chen, Weixin Zhu, Yang Zhao, Yao Yu, Tao Yue, Sidan Du, Xun Cao, and yu zhou

Doc ID: 290223 Received 07 Mar 2017; Accepted 10 May 2017; Posted 10 May 2017  View: PDF

Abstract: In this paper, we present a Spectral Intrinsic Image Decomposition (SIID) model, which is dedicated to resolve a natural scene into its purely independent intrinsic components: illumination, shading and reflectance. By introducing spectral information, our work can solve many challenging cases such as scenes with metameric effects which are hard to tackle for trichromatic intrinsic image decomposition (IID), and thus offers potential benefits to many higher-level vision tasks, e.g., materials classification and recognition, shape-from-shading, and spectral image relighting. A both effective and efficient algorithm is presented to decompose a spectral image into its independent intrinsic components. To facilitate future SIID researches, we present a public dataset with ground-truth illumination, shading, reflectance and specularity and a meaningful error metric, so that the quantitative comparison becomes achieveable. The experiments on this dataset and other images demonstrate the accuracy and robustness of proposed method on diverse scenes, and reveal that more spectral channels indeed facilitate the vision task (i.e., segmentation and recognition)

Bow-shaped Caustics from Conical Prisms: a 13th Century Account of Rainbow Formation from Robert Grosseteste's De iride

Joshua Harvey, Hannah Smithson, Clive Siviour, Giles Gasper, Sigbjorn Sonnesyn, Brian Tanner, and Tom McLeish

Doc ID: 287109 Received 28 Feb 2017; Accepted 11 Apr 2017; Posted 20 Apr 2017  View: PDF

Abstract: The rainbow has been the subject of discussion across a variety of historical periods and cultures, and numerous optical explanations have been suggested. Here, we further explore the scientific treatise De iride [On the Rainbow] written by Robert Grosseteste in the thirteenth century. Attempting to account for the shape of the rainbow, Grosseteste bases his explanation on the optical properties of transparent cones, which he claims can give rise to arc-shaped projections through refraction, i.e. caustics. By stating that atmospheric phenomena are reducible to the geometric optics of a conical prism, the De iride lays out a coherent and testable hypothesis. Through both physical experiment and physics-based simulation we present a novel characterization of cone-light interactions, demonstrating that transparent cones do indeed give rise to bow-shaped caustics; a nonintuitive phenomenon that suggests Grosseteste's theory of the rainbow is likely to have been grounded in observation.

Dependence of depth of focus on spherical aberration of optical systems

Antonin Miks and Jiri Novak

Doc ID: 267338 Received 31 May 2016; Accepted 05 Jul 2016; Posted 06 Jul 2016  View: PDF

Abstract: This paper presents a theoretical analysis and computation of aberration coefficients of the third and fifth order of transverse spherical aberration of an optical system, which generates a ray bundle with a diameter of a geometric-optical circle of confusion smaller than a predetermined limit value. Equations were derived for the calculation of aberration coefficients of an optical system, which satisfy given conditions, and for the determination of the maximum possible depth of focus for given conditions.

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