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Accepted papers to appear in an upcoming issue

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Polarization dynamics induced by parallel optical injection in a single-mode VCSEL

Florian Denis-le Coarer, Ana Quirce, Angel Valle, Luis Pesquera, Marc Sciamanna, Hugo Thienpont, and Krassimir Panajotov

Doc ID: 286507 Received 10 Mar 2017; Accepted 26 Apr 2017; Posted 27 Apr 2017  View: PDF

Abstract: We report an experimental study of the polarization nonlinear dynamics in a 1550-nm single-mode VCSEL subject to parallel optical injection. Experimentally measured stability maps identifying regions of different nonlinear dynamics for various values of bias current are reported. We show that VCSELs with more than 35 dB polarization mode suppression ratio can have a rich nonlinear dynamics in both linear polarizations, including periodic and chaotic behaviors appearing simultaneously in both polarization modes.

Accumulation-layer Surface Plasmons

Shima Fardad, Ernesto Ramos, and Alessandro Salandrino

Doc ID: 292379 Received 07 Apr 2017; Accepted 25 Apr 2017; Posted 26 Apr 2017  View: PDF

Abstract: A rigorous analytical study of the eigenmodes supported by a charge accumulation layer within a transparent conductive oxide (TCO) is presented. The new class of surface plasmons termed Accumulation-Layer Surface Plasmon (ASP) is introduced. Near resonance ASP are tightly bound and display a vast effective index tunability that could be of great practical interest. The suppression of ASP in the presence of epsilon-near zero regions is discussed.

The heart diffraction

Riccardo Borghi

Doc ID: 290934 Received 17 Mar 2017; Accepted 25 Apr 2017; Posted 26 Apr 2017  View: PDF

Abstract: A theoretical study of the plane-wave diffraction by a heart-like sharp-edge aperture corresponding to the involute of a circle is here proposed. Through the recently developed paraxial boundary diffraction wave theory, expressed via the language of catastrophe optics, a unexpected presence of pseudo-nondiffracting regions within the three-dimensional spatial intensity distribution of the diffracted wavefield is intuitively explained and quantitatively characterized. The results of some old beautiful, but nowadays nearly forgotten, diffraction experiments have also been reconsidered from such a peculiar and rather unorthodox perspective.

Real-time phase retrieval of complex optical fields by binary amplitude modulation

Eduardo Peters, Pere Clemente, Eva Salvador Balaguer, Enrique Tajahuerce, Pedro Andres, Dario Perez, and Jesus Lancis

Doc ID: 290501 Received 13 Mar 2017; Accepted 25 Apr 2017; Posted 26 Apr 2017  View: PDF

Abstract: We describe, through simulations and experiments, a real-time wavefront reconstruction technique using random binary amplitude masks and an iterative phase retrieval algorithm based on the Fresnel propagator. By using a digital micromirror device (DMD), it is possible to recover an unknown complex object by illuminating with this set of masks and simultaneously recording the resulting intensity patterns with a high-speed camera. Making this technique suitable for dynamic applications.

Mid-infrared sensing of molecular vibrational modes with tunable graphene plasmons

Tingting Wu, Yu Luo, and Lei Wei

Doc ID: 290780 Received 16 Mar 2017; Accepted 24 Apr 2017; Posted 25 Apr 2017  View: PDF

Abstract: We study the tunable plasmons based on a graphene integrated gold grating structure to sense the vibrational modes of nanometric molecules. The greatly enhanced light-matter interaction and the broadband tunability of the localized graphene plasmonic resonance enable accurate label-free identification of the molecular vibrational modes at subwavelength scale. Our results may accelerate the further development of novel cost-effective biosensors with superior molecular chemical fingerprints sensitivity in an active graphene plasmonic device.

Investigation of the interaction between graphene and planar terahertz metamaterial with toroidal dipolar resonance

Xu Chen and Wen-Hui Fan

Doc ID: 291878 Received 31 Mar 2017; Accepted 24 Apr 2017; Posted 26 Apr 2017  View: PDF

Abstract: A planar terahertz metamaterial consisting of square split ring resonators with three split gaps is proposed and the excitation of toroidal dipolar resonance is demonstrated, accompanying with an extremely high quality factor (189.56). Moreover, we theoretically investigate the strong interaction between graphene and toroidal dipolar resonance of the metamaterial. By varying its Fermi energy, the simulations show that graphene can actively modulate the transmission amplitude of toroidal dipolar resonance and even switch it off. The interaction of the toroidal dipolar resonance with monolayer graphene further highlights the ultrasensitive sensing characteristic of the planar metamaterial, which can be utilized for other graphene-like two-dimensional materials. These intriguing properties of the proposed metamaterial may have potential applications in terahertz modulators and ultrasensitive sensors.

An automated technique to inscribe reproducible Long Period Gratings using a CO2 Laser Splicer

Telmo Almeida, Ricardo Oliveira, Paulo Andre, Ana Rocha, Margarida Facao, and Rogerio Nogueira

Doc ID: 291284 Received 23 Mar 2017; Accepted 23 Apr 2017; Posted 24 Apr 2017  View: PDF

Abstract: We propose a technique to inscribe long period gratings (LPGs) in standard single mode fibers (SSMFs). The proposed method uses a commercial CO2 splicer that allows for the rotation of the fiber during laser irradiation, enabling a uniform exposure around the fiber. LPGs inscribed in SSMFs with different periods are presented. Gratings can be reproduced with a maximum difference between resonant wavelength values of less than 1 nm. Furthermore it is possible to inscribe gratings with attenuation dips of -25 dB while at the same time obtaining polarization dependent losses (PDL) as low as 2 dB.

Combining phase images measured in the radio frequency and the optical frequency ranges

Yoshio Hayasaki and Quang Pham

Doc ID: 287272 Received 22 Feb 2017; Accepted 23 Apr 2017; Posted 24 Apr 2017  View: PDF

Abstract: Phase images measured in the radio frequency (RF) and optical frequency (OF) ranges, whose difference was about 4 × 105, were combined on the basis of a pattern matching method. RF phase imaging was implemented with an optical frequency comb femtosecond laser and a single-pixel camera to measure a meter-order depth object with micrometer-order accuracy. OF phase imaging was implemented with an optical interferometer using a low-coherence femtosecond laser pulses to measure the profile with nanometer-order accuracy and high spatial resolution. Combining the images obtained from both phase measurement systems enabled profilometry of a large depth object with high lateral and axial resolutions.

High Sensitivity Narrowband Wavelength Mid-Infrared Detection at Room Temperature

Romain Demur, Arnaud Grisard, Loic Morvan, Eric Lallier, Nicolas Treps, and Claude Fabre

Doc ID: 287360 Received 24 Feb 2017; Accepted 22 Apr 2017; Posted 24 Apr 2017  View: PDF

Abstract: We report an upconversion experiment using an orientation-patterned gallium arsenide (OP-GaAs) crystal to detect small mid-infrared signals on an InGaAs avalanche photodiode. A conversion efficiency up to 20% with a non-polarized pulsed fiber pump is demonstrated. Our uncooled setup is favorably compared in terms of noise equivalent power, dynamic range and response time to HgCdTe detectors. Its dependence on the polarization of both pump and signal beams is also investigated.

Non-phase-unwrapping interferometric approach for real-time in-plane rotation measurement

Min Lu, Shengjia Wang, Laura Aulbach, Martin Jakobi, and Alexander Koch

Doc ID: 291788 Received 30 Mar 2017; Accepted 22 Apr 2017; Posted 24 Apr 2017  View: PDF

Abstract: This letter proposes a novel interferometric approach for the in-plane rotation measurement. With a simple and compact measurement system, the rotation angle and its direction can be determined simultaneously in real time by applying the spatial carrier frequency. Besides, the phase unwrapping process is not required for the angular evaluation, which simplifies the data processing procedure. Theoretically, the relationship between the in-plane rotation and the phase change distribution has been deduced to demonstrate the possibility of this interferometric method. Practically, the preliminary experiments have been carried out to verify the feasibility of this approach and quantified the measurement accuracy.

Strong magnetic annihilation of the dark mode in a bright-dark coupled terahertz metamaterial

Manukumara Manjappa, Shuvan Prashant Turaga, YOGESH KUMAR SRIVASTAVA, Andrew Bettiol, and Ranjan Singh

Doc ID: 290813 Received 27 Mar 2017; Accepted 22 Apr 2017; Posted 26 Apr 2017  View: PDF

Abstract: Dark mode in metamaterials has become a vital component in determining the merit of Fano type of interference in the system. Its strength dictates the enhancement and suppression in the amplitude and Q-factors of resulting resonance features. In this work, we experimentally probe the effect of strong near field coupling on the strength of dark mode in a concentrically aligned dipole (bright) and the split ring (dark) resonator system exhibiting classical analog of electromagnetically induced transparency effect. A strong magnetic (inductive) coupling between the bright-dark resonators destructively interferes with the inherent magnetic field of the dark mode to completely annihilate the effect of dark mode in the coupled system. Moreover, the observed annihilation of the dark mode can be the basis of resonant optical cloaking effect, wherein under the strong magnetic interactions, the split ring resonator becomes invisible to the incoming terahertz wave.

Stochastic mirage phenomenon in a random medium

Austin McDaniel and Alex Mahalov

Doc ID: 292160 Received 05 Apr 2017; Accepted 20 Apr 2017; Posted 24 Apr 2017  View: PDF

Abstract: In the framework of geometric optics, we consider the problem of characterizing the ray trajectory in a random medium with a mean refractive index gradient. Such a gradient results in the mirage phenomenon where an object's observed location is displaced from its actual location. We derive formulas for the mean ray path in both the situation of isotropic stochastic fluctuations and an important anisotropic case. For the isotropic model, the mean squared displacement is also given by a simple formula. Our results could be useful for applications involving the propagation of electromagnetic waves through the atmosphere, where larger-scale mean gradients and smaller-scale stochastic fluctuations are both present.

Degenerate cavity supporting more than 31 Laguerre-Gaussian modes

Ze-di Cheng, zhaodi liu, xiwang luo, Zhou Zheng Wei, jian wang, qiang li, Yi-Tao Wang, Jian-Shun Tang, Jin-Shi Xu, Chuanfeng Li, and Guang-can Guo

Doc ID: 292910 Received 14 Apr 2017; Accepted 20 Apr 2017; Posted 24 Apr 2017  View: PDF

Abstract: Photons propagating in Laguerre-Gaussian modes have characteristic orbital angular momenta, which are fundamental optical degrees of freedom. The orbital angular momentum of light has potential application in high capacity optical communication and even in quantum information processing. In this work, we experimentally construct a ring cavity with 4 lenses and 4 mirrors that is completely degenerate for Laguerre-Gaussian modes. By measuring the transmitted peaks and patterns of different modes, the ring cavity is shown to supporting more than 31 Laguerre-Gaussian modes. The constructed degenerate cavity opens a new way for using the unlimited resource of available angular momentum states simultaneously.

4.2 PW, 20 fs Ti:Sapphire Laser at 0.1 Hz

Jae Hee Sung, H. W. Lee, J. Y. Yoo, JW Yoon, Chang Won Lee, Jeong Moon Yang, YeonJoo Son, Yong Ha Jang, Seong Ku Lee, and Chang Hee Nam

Doc ID: 291023 Received 22 Mar 2017; Accepted 20 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We demonstrated the generation of 4.2-PW laser pulses at 0.1 Hz from a chirped-pulse amplification Ti:sapphire laser. The cross-polarized wave generation and the optical parametric chirped-pulse amplification stages were installed in the frontend for the prevention of the gain narrowing and for the compensation of the spectral narrowing in the amplifiers, obtaining the spectral width of amplified laser pulses of 84 nm (FWHM) and, additionally, enhancing the temporal contrast. The amplified laser pulses of 112 J after the final booster amplifier were compressed to the pulses with 83 J at 19.4 fs with a shot-to-shot energy stability of 1.5% (RMS). This 4 PW laser will be a workhorse for exploring high field science.

Multiple wavelength stabilization on a single optical cavity using sideband locking technique

Gianmaria Milani, Benjamin Rauf, Piero Barbieri, Filippo Bregolin, Marco Pizzocaro, Pierre Thoumany, Filippo Levi, and Davide Calonico

Doc ID: 287025 Received 28 Feb 2017; Accepted 19 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We implemented a compact, robust and stable device for simultaneous stabilization of lasers with different wavelengths used for the cooling and trapping of atoms in an Yb optical lattice clock. The lasers at 399 nm, 556 nm and 759 nm are locked to a single ultra-stable cavity using the sideband-locking technique, a modified version of the Pound-Drever-Hall method. For the most demanding stabilization here, the 556 nm laser, this system exhibits a 300 Hz linewidth. We observed a long term drift of less than 20 kHz per day at 759 nm that is suitable for operating the lattice laser with a light shift uncertainty below 1×10^{-18}. We successfully tested the system for operating the clock during a typical working day by simultaneously locking the three lasers to the cavity.

A high precise micro-displacement optical-fiber sensor based on surface plasmon resonance

Zongda Zhu, lu liu, Zhihai Liu, Yu Zhang, and Yaxun Zhang

Doc ID: 290272 Received 07 Mar 2017; Accepted 19 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We propose and demonstrate a novel optical-fiber micro-displacement sensor based on surface plasmon resonance (SPR) by fabricating a Kretchmann-configuration on graded-index multimode fiber (GIMMF). We employ a single mode fiber (SMF) to change the radial position of the incident beam as the displacement. In the GIMMF, the angle between light beam and fiber axis, which is closely related to resonance angle, is changed by the displacement, thus the resonance wavelength of fiber SPR shifts. This micro-displacement fiber sensor has a wide detection range of 0-25μm, a high sensitivity of 10.32nm/μm and a nanometer resolution of 2nm, which transcends almost all of other optical fiber micro-displacement sensors. In addition, we also research that increasing the fiber grinding angle or medium refractive index can improve the sensitivity. This micro-displacement sensor will have a great significance in many industrial applications and provide a neoteric, rapid and accuracy optical measurement method in micro-displacement.

Third-harmonic blue light generation from Kerr clustered combs and dispersive waves

Shun Fujii, Takasumi Tanabe, Ryo Suzuki, and Takumi Kato

Doc ID: 290280 Received 07 Mar 2017; Accepted 19 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We demonstrated the generation of blue light emission (438 nm) via the third-harmonic process from an infrared pump by carefully engineering the dispersion of a high quality factor whispering gallery mode microcavity. We present two different approaches to obtaining broad bandwidth light. One is based on a clustered comb and the other employs a dispersive wave, and a broad Kerr comb spanning a half-octave is obtained. This allowed frequency conversion over a broad bandwidth ranging from 438 to 612 nm. This approach will enable the development of micro-scale light sources and frequency converters for future optical processing.

Non-reciprocal geometric phase in nonlinear frequency conversion

Kai Wang, Yu Shi, Alexander Solntsev, Shanhui Fan, Andrey Sukhorukov, and Dragomir Neshev

Doc ID: 285119 Received 13 Feb 2017; Accepted 18 Apr 2017; Posted 18 Apr 2017  View: PDF

Abstract: We describe analytically and numerically the geometric phase arising from nonlinear frequency conversion and show that such a phase can be made non-reciprocal by momentum-dependent photonic transition. Such non-reciprocity is immune to the shortcomings imposed by dynamic reciprocity in Kerr and Kerr-like devices. We propose a simple and practical implementation, requiring only a single waveguide and one pump, while the geometric phase is controllable by the pump and promises robustness against fabrication errors.

The Umov effect in single-scattering dust particles: Effect of irregular shape

Evgenij Zubko, ALYCIA WEINBERGER, Nataliya Zubko, Yuriy Shkuratov, and Gorden Videen

Doc ID: 291058 Received 20 Mar 2017; Accepted 18 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: The Umov effect manifests itself as an inverse correlation between the light-scattering maximum of positive polarization P_max and the geometric albedo A of target. In logarithmic scales, P_max is linearly dependent on A. This effect is long known in optics of particulate surfaces and, recently, it was extended for the case of single-scattering dust particles whose size is comparable to the wavelength of the incident light. In this work we investigate the effect of irregular shape on the Umov effect in single-scattering particles. Using the discrete dipole approximation (DDA), we model light scattering by two different types of irregularly shaped particles. Despite significant differences in their morphology, both types of particles reveal remarkably similar diagrams of log(P_max) vs. log(A). Moreover, in a power-law size distribution r^(–n) with n = 2.5 – 3.0 the Umov diagrams in both types of particles nearly coincide. This suggests little dependence on the shape of target particles in the retrieval of their reflectance using the Umov effect.

A scalable Fourier transform system for instantly structured illumination in lithography

Yan Ye, Fengchuan Xu, Guojun Wei, Yishen Xu, Donglin Pu, Linsen Chen, and Zhiwei Huang

Doc ID: 291410 Received 27 Mar 2017; Accepted 17 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We report the development of a unique scalable Fourier transform 4-f system for instantly structured illumination in lithography. In the 4-f system coupled with a 1-D grating and a phase retarder, the ±1st order of diffracted light from the grating serve as coherent incident sources for creating interference patterns on the image plane. By adjusting the grating and the phase retarder, the interference fringes with consecutive frequencies as well as their orientations and phase shifts can be generated instantly within a constant interference area. We demonstrate that by adapting this scalable Fourier transform system into lithography, the pixelated nano-fringe arrays with arbitrary frequencies and orientations can be dynamically produced in the photoresist with high variation resolution, suggesting its promising application for large area functional materials based on space-variant nanostructures in lithography.

Spatial Integration by a Dielectric Slab Waveguide andits Planar Graphene-based Counterpart

Farzad Zangeneh-Nejad and Amin Khavasi

Doc ID: 290328 Received 08 Mar 2017; Accepted 17 Apr 2017; Posted 18 Apr 2017  View: PDF

Abstract: Motivated by the recent progress in analog computing [Science 343, 160 (2014)], a new approach to perform spatial integration is presented using a dielectric slab waveguide. Our approach is indeed based on the fact that the transmission coefficient of a simple dielectric slab waveguide at its mode excitation angle matches the Green’s function of first order integration. Inspired by the mentioned dielectric-based integrator, we further demonstrate its graphene-based counterpart. The latter is not only reconfigurable but also highly miniaturized in contrast to the previously reported designs [Opt. Commun. 338, 457 (2015)]. Such integrators have the potential to be used in ultrafast analog computation and signal processing.

A multi-petawatt laser facility fully based on optical parametric chirped pulse amplification

Xiaoming Zeng, Kainan Zhou, Yanlei Zuo, Qihua Zhu, Jingqin Su, xiao wang, Xiaodong Wang, Xiaojun Huang, Xuejun Jiang, dongbin Jiang, Yi Guo, Na Xie, Song Zhou, Wu Zhaohui, Jie Mu, Hao Peng, and Feng Jing

Doc ID: 290776 Received 20 Mar 2017; Accepted 17 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We report on a multi-petawatt 3-cascaded all optical parametric chirped pulse amplification laser facility. The experimental results demonstrate that the maximum energy after the final amplifier and after the compressor is 168.7 J and 91.1 J respectively. The pulse width (FWHM) is 18.6 fs after optimization of pulse compression. Therefore, 4.9 PW peak power has been achieved for the laser facility. To the best of our knowledge, this is the highest pulse power reported so far for an all-OPCPA facility, and a compressed pulse shorter than 20 fs is achieved in a petawatt-class laser facility for the first time.

Enhanced performance in serial-to-parallel data conversion via Raman-assisted time lens processing

Junying Ru, Qijie Xie, Chaoran Huang, Bofang Zheng, and Chester C.T. Shu

Doc ID: 290920 Received 21 Mar 2017; Accepted 17 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We have demonstrated a new approach to enhance the uniformity of conversion efficiency in serial-to-parallel data conversion via time lens processing. In our approach, Raman amplification is applied to enhance four-wave mixing in a highly nonlinear fiber. By carefully selecting the pump wavelength, the Raman gain profile can be exploited to compensate the roll-off in conversion efficiency resulted from the varying phase mismatch between the linearly chirped pump and the signal. With Raman amplification, improvement of sensitivity up to 6.8 dB has been experimentally obtained. The variation of sensitivity across the output channels has been reduced from 8.4 to 2.0 dB.

A large-scale nanostructured low-temperature solar selective absorber

Kequn Chi, Liu Yang, Zhaolang Liu, Pingqi Gao, Jichun Ye, and Sailing He

Doc ID: 290704 Received 15 Mar 2017; Accepted 16 Apr 2017; Posted 17 Apr 2017  View: PDF

Abstract: A large-scale nanostructured low-temperature solar selective absorber is demonstrated experimentally. It consists of a silicon dioxide thin film coating on a rough refractory tantalum substrate, fabricated based simply on self-assembled closely-packed polystyrene nanospheres. Because of the strong light harvesting of the surface nanopatterns and constructive interference within the top silicon dioxide coating, our absorber has a much higher solar absorption (0.82) than its planar counterpart (0.68). Though its absorption is lower than that of commercial black paint with ultra-broad absorption, the greatly-suppressed absorption/emission in the long range still enables a superior heat accumulation. The working temperature is as high as 189.6 °C under 7-sun solar illumination in ambient conditions, much higher than those achieved by the two comparables. Therefore, our absorber is very promising in practical solar thermal applications.

Reconfigurable opto-thermal graded-index waveguiding in bulk chalcogenide glasses

Soroush Shabahang, Nicholas Nye, Christos Markos, Demetrios Christodoulides, and Ayman Abouraddy

Doc ID: 291220 Received 22 Mar 2017; Accepted 16 Apr 2017; Posted 17 Apr 2017  View: PDF

Abstract: In the absence of suitable deposition processes, the fabrication of graded-index chalcogenide waveguides or fibers remains an outstanding challenge. Here, by exploiting the strong thermo-optic effect present in chalcogenide glasses, we experimentally demonstrate non-permanent optically-induced waveguides in bulk As$_2$Se$_3$ rods using a 1.55-$\mu$m-wavelength laser. This single-step process can be used not only to self-trap the writing beam, but also to guide another optical beam at a different wavelength in the opto-thermally inscribed waveguide channel. These results could pave the way towards harnessing nonlinear effects in graded-index chalcogenide guided settings.

Surface enhanced infrared absorption of chemisorbed carbon monoxide using plasmonic nanoantennas

Johannes Haase, Salvatore Bagiante, Hans Sigg Hans Sigg, and Jeroen van Bokhoven

Doc ID: 290705 Received 17 Mar 2017; Accepted 14 Apr 2017; Posted 14 Apr 2017  View: PDF

Abstract: We report the enhancement of infrared absorption of chemisorbed carbon monoxide on platinum in the gap of plasmonic nanoantennas. Our method is based on the self-assembled formation of platinum nano islands on nanoscopic dipole antenna arrays manufactured via electron beam lithography. We employ systematic variations of the plasmonic antenna resonance to precisely couple to the molecular stretch vibration of carbon monoxide adsorbed on the platinum nano islands. Ultimately we reach more than 1500 fold infrared absorption enhancements allowing for an ultrasensitive detection of a monolayer of chemisorbed carbon monoxide. The developed procedure can be adapted to other metal adsorbents and other molecular species and could for instance be utilized for coverage sensing in surface catalytic reactions.

Non-Resonant Modes in Plasmonic Holey Metasurfaces for the Design of Artificial Flat Lenses

Guido Valerio, Zvonimir Sipus, Anthony Grbic, and Oscar Quevedo-Teruel

Doc ID: 291037 Received 22 Mar 2017; Accepted 14 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: This paper discusses non-resonant modes excited on holey metasurfaces, and their influence on the properties of spoof plasmonic states supported by the metasurface when a second surface is placed in its proximity. We consider here a metallic surface with periodic holes drilled in it. The field excited on each hole is projected onto a set of non-resonant modes in order to discuss their relative relevance. While previous simpler models were assuming only the presence of the fundamental mode, we show that the simultaneous presence of several modes occurs when the surface is placed next to a metallic plate. Therefore, higher-order modes are responsible for the peculiar physical properties of wave propagation of spoof plasmons between two surfaces, which can lead to new gradient-index flat lenses for transceivers for space communications.

Semitransparent and flexible perovskite solar cell with high visible transmittance based on ultrathin metallic electrodes

XiaLi Ou, Jing Feng, Ming Xv, and Hong-Bo Sun

Doc ID: 285326 Received 13 Feb 2017; Accepted 13 Apr 2017; Posted 14 Apr 2017  View: PDF

Abstract: Herein, we fabricated semitransparent and flexible indium-free perovskite solar cells (PeSCs) with high visible transmittance employing two kinds of composite ultrathin metallic electrodes, MoO₃/Au and MoO₃/Au/Ag/MoO₃/Alq₃, as bottom and top electrodes, respectively. These electrodes show superb electrical conductivity, excellent mechanical robustness and high optical transparency which are quite suitable for semitransparent and flexible PeSCs. An overall power conversion efficiency (PCE) of 6.96% and an average visible transmittance (AVT) of 18.16% in the wavelength range of 380-790 nm were achieved. Furthermore, the devices maintained 71% of its initial PCE after 1000 bending cycles with a bending radius of 4 mm.

Asymmetric LMA rod-type fiber for enhanced higher order mode delocalization

Zeinab Sanjabi Eznaveh, Jose Antonio-Lopez, James Anderson, Axel Schulzgen, and Rodrigo Amezcua Correa

Doc ID: 286876 Received 16 Feb 2017; Accepted 12 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We present a novel design of micro-structured large pitch, large-mode-area (LMA) asymmetric rod-type fiber. By reducing the cladding symmetry through six high refractive index germanium-doped silica inclusions, the fiber features strong higher-order mode (HOM) delocalization leading to a potentially enhanced preferential gain for the fundamental mode in active fibers. In addition, high resolution spatially and spectrally (S2) resolved mode analysis measurements confirm HOM contributions below 1% and LP1m-like HOM contributions below the detection limit. This proposed fiber design enables single mode operation, with close to diffraction limited beam quality of M2 = 1.3 and an effective mode area of 2560 μm2 at 1064 nm. This design opens up new insights into mitigating the threshold-like onset of modal instabilities (MI) in high power fiber lasers and fiber amplifiers by efficiently suppressing LP11 modes.

Photonics sensing at the thermodynamic limit

George Skolianos, Arushi Arora, Martin Bernier, and Michel Digonnet

Doc ID: 285312 Received 23 Jan 2017; Accepted 12 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: We report a slow-light fiber Bragg grating strain sensor with a resolution limited by the extremely low thermodynamic phase fluctuations of the fiber. This was accomplished by using a short grating (4.5 mm) to enhance the thermal phase noise, an ultra-stable interrogation laser to lower the laser frequency noise, and a slow-light mode with a high group index (~533) tosuppress all other noise sources. We demonstrate that in a similar but longer grating (21 mm), phase noise is suppressed in inverse proportion to the square root of the length, in accord with theory, leading to a strain resolution as low as 130 fε/√Hz and a minimum detectable length of ~3x10-15 m at 1.5 kHz.

Active modulation of the terahertz spectra radiated from two air plasmas

Ying Zhang, wenfeng sun, Xinke Wang, Jiasheng Ye, Shengfei Feng, Peng Han, and Yan Zhang

Doc ID: 286017 Received 02 Feb 2017; Accepted 12 Apr 2017; Posted 17 Apr 2017  View: PDF

Abstract: A simple and energy-saving method has been proposed to actively modulate the spectra of terahertz waves radiated from two serial plasmas, which uses the background light to generate one plasma to make full use of the energy of the femtosecond laser. With this method, the modulation of the central frequency, spectral bandwidth, spectral profile of the output terahertz waves have been observed. The shifting of the frequency split has been manipulated by changing the distance of the two serial plasmas. The manipulation results agree with the ones simulated by transition-Cherenkov model. This proposed method provides a useful tool for getting the modulated terahertz spectra that can be used in the terahertz remote sensing.

Laguerre-Gaussian modal q-plates

Etienne Brasselet and Mushegh Rafayelyan

Doc ID: 287548 Received 27 Feb 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We propose space-variant uniaxial flat optical elements designed to generate pure Laguerre-Gaussian modes with arbitrary azimuthal and radial indices $l$ and $p$ by considering the fundamental case of an incident Gaussian beam. This is done via the combined use of the dynamic and the geometric phases. Optimal design protocol for the mode conversion efficiency is derived and the corresponding characteristics are given for $-6 \leq l \leq 6$ and $0 \leq p \leq 5$. The obtained ``modal q-plates' may find many applications whenever the radial degree of freedom of a light field is at play.

Absolute frequency measurements of CHF₃ Doppler-free ro-vibrational transitions at 8.6 µm

Gianluca Galzerano, Alessio Gambetta, Edoardo Vicentini, Yuchen Wang, Nicola Coluccelli, Eugenio Fasci, Livio Gianfrani, Antonio Castrillo, Valentina Di Sarno, Luigi Santamaria, Pasquale Maddaloni, Paolo De Natale, and Paolo Laporta

Doc ID: 287557 Received 27 Feb 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We report on absolute measurements of saturated-absorption line-centers frequencies of room-temperature trifluoromethane using a quantum cascade laser at 8.6 µm and the frequency modulation spectroscopy method. Absolute calibration of the laser frequency is obtained by direct comparison with a mid-infrared optical frequency comb synthesizer referenced to a rf Rb standard. Several sub-Doppler transitions falling in the υ₅ vibrational band are investigated at around 1158.9 cm^{-1} with a fractional frequency precision of 8.6x10^{-12} at 1-s integration time, limited by the Rb-clock stability. The demonstrated frequency uncertainty of 6.6x10^{-11} is mainly limited by the reproducibility of the frequency measurements.

Pulse picker for synchrotron radiation driven by surface acoustic wave

Simone Vadilonga, Ivo Zizak, Dmitry Roshchupkin, Andrei Petsiuk, Igor Dolbnya, Kawal Sawhney, and Alexei Erko

Doc ID: 290474 Received 23 Mar 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: A functional test for a pulse picker for synchrotron radiation was performed at Diamond Light Source. The purpose of a pulse picker is to select which pulse from the synchrotron hybrid mode bunch pattern reaches the experiment. In the present work, the Bragg reflection on a Si/B4C multilayer was modified using surface acoustic wave (SAW) trains. Diffraction on the SAW alters the direction of the X-rays and it can be used to modulate the intensity of the X-rays that reach the experimental chamber. Using electronic modulation of the SAW amplitude it is possible to obtain different scattering conditions for different X-ray pulses.To isolate the single bunch, the state of the SAW must be changed in the short time gap between the pulses.To achieve the necessary time resolution the measurements have been performed in conical diffraction geometry. The achieved time resolution was 120 ns.

Thermo-optic characteristic of DNA thin solid film and its application as a biocompatible optical fiber temperature sensor

Seongjin Hong, Woohyun Jung, Tavakol Nazari, Sanggwon Song, Kyunghwan Oh, Chai Quan, and Taeoh Kim

Doc ID: 290612 Received 15 Mar 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We report a unique thermo-optical characteristics of DNA-CTMA (DNA-Cetyl tri-methyl ammonium) thin solid film with a large negative thermo-optical coefficient of -3.4 10-4/˚C in the temperature range from 20 ~ 70˚C without any observable thermal hysteresis. By combining this thermo-optic DNA film and fiber optic multimode interference (MMI) device, we experimentally demonstrated a highly sensitive compact temperature sensor with a large spectral shift of 0.15nm/˚C. The fiber optic MMI device was a concatenated structure with single mode fiber (SMF)-coreless silica fiber (CSF)-single mode fiber (SMF) and the DNA-CTMA film was deposited on the CSF. The spectral shifts of the device in experiments were compared with beam propagation method, which showed a good agreement.

Second-harmonic focusing by nonlinear turbid medium via feedback-based wavefront shaping

Yanqi Qiao, Yajun Peng, Yuanlin Zheng, Fangwei Ye, and Xianfeng Chen

Doc ID: 291059 Received 22 Mar 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: Scattering has usually been considered detrimental for optical focusing or imaging. Recently, more and more research has shown that strongly scattering materials can be utilized to focus coherent light by controlling or shaping the incident light. Here, purposeful focusing of second-harmonic waves, which are generated and scattered from nonlinear turbid media via feedback-based wavefront shaping is presented. This work shows a flexible manipulation of both disordered linear and nonlinear scattering signals, indicating more controllable degrees of freedom for the description of turbid media. This technique also provides a possible way to an efficient transmission of nonlinear signal at a desired location in the form of a focal point or other patterns. With the combination of random nonlinear optics and wavefront shaping methods, more interesting applications can be expected in the future, such as nonlinear transmission matrix, multi-frequency imaging and phase-matching-free nonlinear optics.

Programmable controlled mode-locked fiber laser using a digital micromirror device

Wu Liu, Jintao Fan, Chen Xie, Youjian Song, CHENGLIN Gu, Lu Chai, Qingyue Wang, and Ming-lie Hu

Doc ID: 291531 Received 29 Mar 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: A digital micromirror device (DMD) based arbitrary spectrum amplitude shaper is incorporated into a large-mode-area photonic crystal fiber (LMA-PCF) laser cavity. The shaper acts as an in-cavity programmable filter and provides large tunable dispersion from normal to anomalous. As a result, mode-locking is achieved in different dispersion regimes. By programming different filter profiles on the DMD, the laser generates femtosecond pulse with tunable central wavelength and controllable bandwidth. Under conditions of suitable cavity dispersion and pump power, design-shaped spectra are directly obtained by varying the amplitude transfer function of the filter. The results show the versatility of the DMD based in-cavity filter for flexible control of the pulse dynamics in mode-locked fiber laser.

Absolute non-invasive measurement of CO2 mole fraction emitted by E. coli and S. aureus using calibration-free 2f WMS applied to a 2004 nm VCSEL

Zarin S., Arup Chakraborty, and abhishek upadhyay

Doc ID: 281991 Received 23 Dec 2016; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We report the first demonstration of accurate real-time non-invasive measurement of the absolute cumulative mole fraction of metabolic carbon dioxide emitted by Escherichia coli and Staphylococcus aureus over a period of several hours of their life cycles using a recently-developed calibration-free wavelength modulation spectroscopy technique. A 1mW vertical cavity surface emitting laser is used to interrogate a single rotational vibrational absorption line of carbon dioxide at 2003.5 nm. The measurements are immune to laser intensity fluctuations due to variable optical coupling that is inevitable in such free-space coupled experiments that run over 10-18 hours. The cumulative carbon dioxide mole fraction follows the characteristic modified Gompertz model that is typical of bacterial growth in batch cultures. The various characteristics growth parameters are extracted from this curve. The technique can be readily extended to study multiple volatile organic compounds that bacteria are known to emit.

Cavity enhanced thermo-optic bistability and hysteresis in a graphene-on-Si₃N₄ ring resonator

Yun Gao, Wen Zhou, Xiankai Sun, Hon Tsang, and Chester C.T. Shu

Doc ID: 285801 Received 30 Jan 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: Cavity enhanced thermo-optic bistability is studied in a graphene-on-Si₃N₄ ring resonator. By engineering the coverage of monolayer graphene on top of the Si₃N₄ ring resonator, we observe a twofold enhancement in the thermo-optically induced resonance shift rate and 18-fold increase in the effective nonlinear refractive index compared with the devices without graphene. The thermo-optic hysteresis loop is also characterized in this hybrid structure, where the experimental results agree well with the theoretical calculations. This study paves the way for the design of graphene-on-Si₃N₄ based high-speed photodetectors, modulators, and devices for on-chip nonlinear optical applications.

High-reflectance magnetron sputtered Sc-based x-ray multilayer mirrors for the water window

Catherine Burcklen, Franck DELMOTTE, Evgueni Meltchakov, david DENNETIÈRE, Blandine CAPITANIO, DE ROSSI Sébastien, and Francois Polak

Doc ID: 286084 Received 17 Feb 2017; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We present an experimental comparison of several Sc-based short period multilayer mirrors including Cr/Sc with B4C barrier layers and CrNx/Sc and we propose a new material combination that provides high reflectance in the water window domain. Multilayer samples with period thickness in the range 1.5 nm to 1.7 nm have been deposited by magnetron sputtering and characterized by x-ray reflectometry with a Cu-Kα source and with synchrotron radiation near the Sc-L2,3 edge. Best results are achieved by combining the nitridation of Cr layers and the addition of B4C barrier layers. Near normal incidence reflectance as high as % has been measured at photon energy of 397 eV. A simulation model of the multilayer structure is proposed and predicts that reflectance higher than 32% are achievable with CrNx/B4C/Sc mirrors.

Mirrors with Inverse Offset-Dependent Focal Length for Multi-Pass Cavities

Sarper Ozharar and Alphan Sennaroglu

Doc ID: 286724 Received 16 Feb 2017; Accepted 11 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We present a novel multi-pass-cavity (MPC) design based on the use of a rotationally symmetric end mirror whose focal length varies inversely as the ray height from the optical axis. We provide a detailed discussion of how ray tracing can be done for this system and show with numerical simulations, that a very rich set of exotic spot patterns can be formed on the end mirrors. We further show a specific q-preserving configuration where the q-parameters of the input and output beam remain the same. Finally, we derive the polar form of the mirror surface profile that gives this offset-dependent focal length.

Terahertz multilevel phase Fresnel lenses fabricated by laser patterning of silicon

Linas Minkevicius, Simonas Indrišiūnas, Ramūnas Šniaukas, Bogdan Voisiat, Vytautas Janonis, Vincas Tamošiūnas, Irmantas Kašalynas, Gediminas Račiukaitis, and Gintaras Valušis

Doc ID: 287646 Received 28 Feb 2017; Accepted 11 Apr 2017; Posted 12 Apr 2017  View: PDF

Abstract: Multilevel Phase Fresnel Lenses (MPFLs) with high numerical aperture (NA) for terahertz (THz) frequencies were developed. The components based on monocrystalline silicon wafer are prepared by patterning by a high-speed industrial-scale laser-direct-write (LDW) system. Two consistent series of the THz-MPFLs with number of subzones varying between 2 and 1643 and the focal length of 5 mm and 10 mm were produced employing inherent flexibility of the three-dimensional (3D) DLW fabrication process. The focusing performance was studied at the optimal 0.58 THz frequency using a Gaussian beam profile and scanning 2D intensity distribution with THz detector along the optical axis. The efficiency of THz-MPFL was found to be dependent of the number of subzones. The position and orientation angle of the patterned plane of the silicon wafer were considered to reduce the effect of standing waves formation in the experiment.

Performance comparison of pseudo-inverse and maximum-likelihood estimators of Stokes parameters in the presence of Poisson noise for spherical design-based measurement structures

Francois Goudail

Doc ID: 291790 Received 30 Mar 2017; Accepted 11 Apr 2017; Posted 17 Apr 2017  View: PDF

Abstract: Estimation of the Stokes vector from N>4 intensity measurements is usually performed with the pseudo-inverse (PI) estimator, which is optimal when the noise that corrupts the measurements is additive and Gaussian. In the presence of Poisson shot noise, the maximum-likelihood (ML) estimator is different from the PI estimator, but is more complex to implement since it is not closed-form. We compare in this Letter the precisions obtained with the ML and the PI estimators in the presence of Poisson noise when using measurement structures based on spherical designs. We show that in this case, the gain in precision brought by the ML estimator is real but modest, so that in applications where processing speed is an issue, the PI estimator can be considered sufficient. This result is important in the choice of the inversion strategy for Stokes polarimetry.

Highly scalable femtosecond coherent beam combining demonstrated with 19 fibers

LE DORTZ Jérémy, anke heilmann, Marie Antier, Jerome Bourderionnet, Christian Larat, Ihsan Fsaifes, Louis Daniault, severine bellanger, Christophe Simon-Boisson, Jean-Christophe Chanteloup, Eric Lallier, and Arnaud Brignon

Doc ID: 288010 Received 08 Mar 2017; Accepted 10 Apr 2017; Posted 12 Apr 2017  View: PDF

Abstract: Coherent beam combining in the femtosecond regime of a record number of 19 fibers is demonstrated. The interferometric phase measurement technique, particularly well-suited to phase-lock a very large number of fibers, is successfully demonstrated in the femtosecond regime. A servo-loop is implemented to control piezo-electric fiber stretchers for both phase and delay variations compensation. The residual phase errors are below λ/60 rms. Nearly 50 % of the total energy is contained in the far field central lobe. After compression we obtain a combined pulse width of 300 fs identical to the master oscillator pulse width.

Ultra-slow light propagation by self-induced transparency in ruby in the superhyperfine limit

Hans Riesen, Aleksander Rebane, Rajitha Rajan, Wayne Hutchison, Steffen Ganschow, and Alex Szabo

Doc ID: 285878 Received 01 Feb 2017; Accepted 10 Apr 2017; Posted 12 Apr 2017  View: PDF

Abstract: Self-induced transparency is reported for circularly polarized light in the R1(-3/2) line of 30 ppm ruby (α-Al2O3:Cr3+) at 1.7 K in a magnetic field of B||c=4.5 T. In such a field and temperature a 30 ppm ruby is in the so-called superhyperfine limit resulting in a long phase memory time, TM=50 μs, and a thousand-fold slower pulse propagation velocity of ~300 m/s was observed, compared to the ~300 km/s measured in the first observation of SIT ~50 year ago, that employed ruby with a 500 ppm chromium concentration in zero field and at 4.2 K. To date this is the slowest pulse propagation ever observed in a SIT experiment.

Direct Stabilization of Optomechanical Oscillators

Ke Huang and Mani Hossein-Zadeh

Doc ID: 286974 Received 16 Mar 2017; Accepted 10 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We demonstrate a simple and effective technique for stabilizing the oscillation amplitude of a radiation pressure driven optomechanical RF oscillator (OMO). By controlling the optomechanical gain through a feedback loop that uses the oscillation amplitude itself as the feedback parameter, we have been able to suppress the amplitude fluctuations and drift. In contrast to more complex techniques that only fix the relative wavelength detuning, the proposed technique isolates the oscillation amplitude not only from laser wavelength variations but also laser power variations, ambient temperature variations and coupling gap variations. The amplitude stabilization also improves the stability of the oscillation frequency (compared to free running OMOs).

Self-compression of femtosecond deep-ultraviolet pulses by filamentation in krypton

Shunsuke Adachi and Toshinori Suzuki

Doc ID: 287380 Received 23 Feb 2017; Accepted 10 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We demonstrate self-compression of deep-ultraviolet (DUV) pulses by filamentation in krypton. In contrast to self-compression in the near-infrared, that in the DUV is associated with a red-shifted leading edge appearing in the pulse temporal profile. The achieved pulse width of 15 fs is the shortest among demonstrated sub-mJ deep-ultraviolet pulses.

5.6 W monolithic fiber laser at 3.55 μm

Frédéric Maes, Vincent Fortin, Martin Bernier, and Real Vallee

Doc ID: 288039 Received 06 Mar 2017; Accepted 10 Apr 2017; Posted 26 Apr 2017  View: PDF

Abstract: We report the first monolithic erbium-doped fluorozirconate fiber laser bounded by two fiber Bragg gratings (FBG) operating near 3.55 μm. Its output power and total optical efficiency are 5.6 W and 26.4 % respectively, the highest ever achieved at this wavelength from a fiber laser. The monolithic design of the cavity also increases its stability and prevents fiber tip damage which has limited prior demonstrations to a maximum output power of 1.5 W. This Letter also studies the performances of the laser cavity for various output FBG reflectivities and presents numerical modeling results exhibiting remarkable agreement with experimental results.

Designing ultrabroadband absorbers/emitters based on Bloch theorem and optical topological transition

Yinhui Kan, Changying Zhao, Xing Fang, and Boxiang Wang

Doc ID: 288035 Received 06 Mar 2017; Accepted 09 Apr 2017; Posted 12 Apr 2017  View: PDF

Abstract: In this paper, we propose a method to design ultrabroadband near-perfect absorbers/emitters, consisting of periodic dielectric-metal multilayer. In the method, Bloch theorem and optical topological transition (OTT) of isofrequency surfaces are employed to manipulate the starting and end of near-perfect spectral absorption band, respectively. Moreover, we design and fabricate an ultrabroadband near-perfect absorber utilizing the proposed method. The average absorption of the designed absorber is ~95% in the focused visible and near-infrared range (0.4-2 μm). This omnidirectional and polarization-independent near-perfect absorber ispromising for solar energy harvesting, emissivity control and thermal imaging.

Uncloaking diffusive-light invisibility cloaks by speckle analysis

Andreas Niemeyer, Frederik Mayer, Andreas Naber, Milan Koirala, Alexey Yamilov, and Martin Wegener

Doc ID: 285550 Received 25 Jan 2017; Accepted 08 Apr 2017; Posted 21 Apr 2017  View: PDF

Abstract: Within the range of validity of the stationary diffusion equation, an ideal diffusive-light invisibility cloak can make an arbitrary macroscopic object hidden inside of the cloak indistinguishable from the surrounding for all colors, polarizations, and directions of incident visible light. However, the diffusion equation for light is an approximation which becomes exact only in the limit of small coherence length. Thus, one expects that the cloak can be revealed by illumination with coherent light. The experiments presented here show that the cloaks are robust in the limit of large coherence length but can be revealed by analysis of the speckle patterns under illumination with partially coherent light. Experiments on cylindrical core-shell cloaks and corresponding theory are in good agreement.

Resolving 1 million sensing points in an optimized differential time-domain Brillouin sensor

Alejandro Dominguez-Lopez, Marcelo Soto, Sonia Martin-Lopez, Luc Thevenaz, and Miguel Gonzalez Herraez

Doc ID: 284561 Received 19 Jan 2017; Accepted 06 Apr 2017; Posted 07 Apr 2017  View: PDF

Abstract: A differential pulse-width pair (DPP) Brillouin distributed fiber sensor is implemented to achieve centimetric spatial resolution over distances of several kilometers. The presented scheme uses a scanning method in which the spectral separation between the two probe sidebands is kept constant, while the optical frequency of the pump is swept to scan the Brillouin spectral response. Experimental results show that this method avoids detrimental temporal distortions of the pump pulses, which in a standard implementation prevents the DPP method to operate over mid-to-long distances. Such novel scanning procedure allows resolving, for the first time in pure time-domain Brillouin sensors, 1’000’000 sensing points, i.e., 1 cm spatial resolution over 10 km in a conventional acquisition time.

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