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Accepted papers to appear in an upcoming issue

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Impact of Multipath Effects on Theoretical Accuracy of TOA-based Indoor VLC Positioning System

Xuqing Sun, Yonggang Zou, Jingyuan Duan, and Ancun Shi

Doc ID: 242843 Received 17 Jun 2015; Accepted 31 Aug 2015; Posted 01 Sep 2015  View: PDF

Abstract: The time-of-arrival (TOA) method, based on indoor visible light communication (VLC) positioning system, in a non-line-of sight (NLOS) environment is analyzed in this paper. NLOS delay is assumed to be Gamma distributed. The theoretical accuracy is calculated by deriving the Generalized Cramer–Rao Lower Bound (G-CRLB) for multipath propagation. The impact of multipath effects on G-CRLB is analyzed in theory. We then discuss the physical meaning of the Gamma distribution parameters and their influences to positioning accuracy. Finally, we give a numerical simulation of G-CRLB with a range of typical parameter values. The result proves that for the average transmitted optical power of only 3 W, the positioning accuracy is under 1 cm in a NLOS environment.

Investigation on Hybrid Microring Lasers Adhesively Bonded on Silicon Wafer

Yong-Zhen Huang, Shao Shuai Sui, Ming-Ying Tang, Yue-De Yang, Jin-Long Xiao, and Yun Du

Doc ID: 241196 Received 18 May 2015; Accepted 30 Aug 2015; Posted 01 Sep 2015  View: PDF

Abstract: Thermal characteristics are numerically investigated for the hybrid AlGaInAs/InP on silicon microring lasers with different ring radii and widths. Low threshold current and low active region temperature rise are expected for the microring laser with a narrow ring width. Based on the thermal analysis and the three-dimensional simulation for mode characteristics, hybrid AlGaInAs/InP on silicon microring lasers with an inner n-electrode laterally confined by the p-electrode metallic layer are fabricated using adhesively bonding technique. A threshold current of 4 mA is achieved for a hybrid microring laser with a radius of 20 μm and a ring width of 3.5 μm at 12 °C, and the corresponding threshold current density is as low as 1 kA/cm2. The influence of the location of silicon waveguide on output performance is studied experimentally for improving the output coupling efficiency. Furthermore, continuous-wave electrically injected lasing up to 55 °C is realized for a hybrid microring laser with a radius of 30 μm and a ring width of 3 μm

Graphene surface plasmon polaritons transport on curved substrates

Tinghui Xiao, Lin Gan, and Zhiyuan Li

Doc ID: 243216 Received 17 Jun 2015; Accepted 27 Aug 2015; Posted 27 Aug 2015  View: PDF

Abstract: We theoretically investigate the transport property of graphene surface plasmon polaritons (GSPPs) on curved graphene substrates. The dispersion relationship, propagation length and field confinement are calculated by an analytical method and compared with those on planar substrates. Based on our theory, the bend of graphene nearly does not affect the property of GSPPs except an extremely small shift to the lower frequency for the same effective mode index. The field distributions and the eigenfrequencies of GSPPs on planar and cylindrical substrates are calculated by finite element method, which validates our theoretical analysis. Moreover, three types of graphene guided optical interconnections of GSPPs, namely, planar to curved graphene film, curved to planar graphene film, and curved to curved graphene film, are proposed and examined in details. The theoretical results show that the GSPPs propagation on curved graphene substrates and interconnections will not induce any additional losses if the phase matching condition is satisfied. Additionally, the extreme tiny size of curved graphene for interconnection at a certain spectra range is predicted by our theory and validated by the simulation of 90 degree turning of GSPPs. The bending effect on the property of GSPPs is systematically analyzed and identified. Our studies would be helpful to instruct design of plasmonic devices involving curved GSPPs, such as nanophotonic circuits, flexible plasmonic and biocompatible devices.

Optical trapping and orientation of Escherichia coli cells using two tapered fiber probes

Jianbin Huang, Xiaoshuai Liu, Yao Zhang, and Baojun Li

Doc ID: 245904 Received 14 Jul 2015; Accepted 26 Aug 2015; Posted 27 Aug 2015  View: PDF

Abstract: We report optical trapping and orientation of Escherichia coli (E. coli) cells by using two tapered fiber probes. With a laser beam at 980 nm wavelength launched into the probe I, an E. coli chain consisted of three cells was formed at the tip of probe I. After launching a beam at 980 nm into the probe II, the E. coli at the end of the chain was trapped and oriented via the optical torques yielded by two probes. The orientation of the E. coli was controlled by adjusting the laser power of probe II. Experimental results were interpreted by theoretical analysis and numerical simulations.

Deep-UV fluorescence lifetime imaging microscopy

Saulius Juodkazis, Christiaan de Jong, Alireza Lajevardipour, Mindaugas Gecevicius, Martynas Beresna, Gediminas Gervinskas, Peter Kazansky, Yves Bellouard, and Andrew Clayton

Doc ID: 244203 Received 02 Jul 2015; Accepted 22 Aug 2015; Posted 24 Aug 2015  View: PDF

Abstract: A novel fluorescence lifetime imaging microscope (FLIM) working with deep UV 240-280~nm wavelength excitations is developed. UV-FLIM is used for measurement of defect related fluorescence and its changes upon annealing from femtosecond laser-induced modifications in fused silica. This FLIM technique can be used with micro-fluidic and bio-samples to characterize temporal characteristics of fluorescence upon UV excitation, a capability easily added to a standard microscope-based FLIM. UV-FLIM was tested to show an annealing of the defects induced by silica structuring with ultra-short laser pulses. Frequency-domain fluorescence measurements were converted into the time-domain to extract long fluorescence lifetimes from defects in silica.

High-Q silica microdisk optical resonators with large wedge angles on a silicon chip

Xiaoshun Jiang, Guanyu Li, Pei Liu, Chao Yang, Jiyang Ma, Hongya Wu, and Min Xiao

Doc ID: 245803 Received 17 Jul 2015; Accepted 18 Aug 2015; Posted 20 Aug 2015  View: PDF

Abstract: We experimentally demonstrate high optical quality factor silica microdisk resonators on a silicon chip with large wedge angles by reactive ion etching. For 2-µm-thick microresonators, we have achieved wedge angles of 59°, 63°, 70° and 79° with optical quality factors of 2.4×10⁷, 8.1×10⁶, 5.9×10⁶ and 7.4×10⁶, respectively, from ~80-µm-diameter microresonators in the 1550 nm wavelength band. Also, for 1-µm-thick microresonators, we have obtained optical quality factor of 7.3×10⁶ with a wedge angle of 74°.

Ray-optics model for optical force and torque on a spherical metal-coated Janus microparticle

JING LIU, Chao Zhang, Yiwu Zong, Honglian Guo, and Zhiyuan Li

Doc ID: 243860 Received 09 Jul 2015; Accepted 10 Aug 2015; Posted 11 Aug 2015  View: PDF

Abstract: In this paper, we develop a theoretical method based on ray optics to calculate the optical force and torque on a metallo-dielectric Janus particle in an optical trap made from a tightly focused Gaussian beam. The Janus particle is a 2.8 μm in diameter polystyrene sphere half-coated with a gold thin film of several nanometers in thickness. The calculation result shows that the focused beam will push the Janus particle away from the center of trap and the equilibrium position of the Janus particle where the optical force and torque are both zero is located in a circular orbit surrounding the laser beam axis. The theoretical results are in good agreement qualitatively and quantitatively with the experimental observation made by us. As the ray-optics model is simple in principle, user friendly in formalism, and very cost effective in terms of computation resources and time compared with other usual rigorous electromagnetics approaches, the developed theoretical method can become an invaluable tool to deeply understand and design novel ways to control the mechanical motion of complicated microscopic particles in various optical tweezers.

Faraday anomalous dispersion optical filter at 133Cs weak 459 nm transition

Jingbiao Chen, Xiaobo Xue, Duo Pan, xiaogang zhang, Bin Luo, and Hong Guo

Doc ID: 244301 Received 04 May 2015; Accepted 06 Aug 2015; Posted 11 Aug 2015  View: PDF

Abstract: A 459 nm Faraday anomalous dispersion optical filter (FADOF) working at the side wings of the cesium 6S1/2 → 7P1/2 transition with weak oscillator strength is achieved. The transmittance of the higher side wing reaches 98% at temperature 179℃and magnetic field above 323 G. The experimental results coincide with the theoretical predictions in 1982 and 1995, which was not realized in experiment over three decades. Due to its high transmittance, high accuracy and narrow linewidth, the 459 nm FADOF can be applied in underwater optical communications, building of active optical clocks and laser frequency stabilization in active optical clocks.

Subnanosecond KTP OPO intracavity pumped by a Kerr-lens mode-locked YVO4/Nd:YVO4 laser coupled with an AOM

Hongwei Chu, Jia Zhao, Kejian Yang, Shengzhi Zhao, Tao Li, Dechun Li, Guiqiu Li, and qiaowen chao

Doc ID: 243524 Received 22 Jun 2015; Accepted 27 Jul 2015; Posted 29 Jul 2015  View: PDF

Abstract: A Kerr-lens mode-locked (KLM) YVO4/Nd:YVO4 laser coupled with the acousto-optic modulator (AOM) Q-switching near 1064 nm was employed to pump an intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO). Subnanosecond signal wave near 1572 nm with low repetition rate was realized. At an AOM repetition rate of 8 kHz, the maximum output power was 165 mW. The highest pulse energy, the shortest duration and the highest peak power of a mode-locking signal pulse were estimated to be ~ 10.3 μJ, ~ 120 ps and ~ 82 kW, respectively.

Computational Investigation of InxGa1−xN/GaN Quantum Dot Intermediate Band Solar Cell

Dr Mohammad Monirujjaman Khan and Raqibull Hasan

Doc ID: 236140 Received 19 Mar 2015; Accepted 23 Jul 2015; Posted 29 Jul 2015  View: PDF

Abstract: The development of high-performance solar cell using InxGa1−xN quantum dots (QDs) is an important goal when compared with the existing single/multi junction solar cell. From this perspective, InxGa1-xN /GaN quantum dot intermediate band (QDIB) solar cell is a promising candidate for exceeding the Shockley-Queisser power conversion efficiency limit of a single p-n junction solar cell. In this paper, the performance of InxGa1-xN /GaN QD-IBSC has been analyzed by solving the Schrodinger equation using Kronig-Penney model in finite potential well. In addition, two important parameters which include open circuit voltage (Voc) and short circuit current (Jsc) have been also presented with the variation of indium composition in quantum dot (QD) materials. However, the power conversion efficiency is worked out based on particular assumptions. The results show that the greater the size of QD and interdot distance (ID) leads to poor power conversion efficiency. Moreover, the maximum power conversion efficiency is noticed to be 62.84% for the position of intermediate band at 2eV energy state in the barrier region.

Compact 517 MHz mode locked Er:fiber soliton ring fiber laser

Jian Zhang, Ziyun Kong, Yizhou Liu, Aimin Wang, and Zhigang Zhang

Doc ID: 240037 Received 29 Apr 2015; Accepted 04 Jul 2015; Posted 24 Aug 2015  View: PDF

Abstract: We report a compact passive mode-locked Er:fiber ring laser operated at the fundamental repetition rate of 517 MHz, which we believe the highest fundamental repetition rate ever reported in a ring cavity fiber laser. The key technique is the employment of two innovative high-power WDM-collimators with all gain fiber cavity to suit for the high power (up to 2~W) pumping. The laser is featured with the direct chirp-free output pulse which is 97 fs without extra-cavity compression at an average output power of 90 mW.

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