Optical phase conjugation for ultra long-haul phase-shift-keyed transmission

Nonlinear phase noise (Gordon-Mollenauer phase noise) can limit the transmission distance for phase-shift-keyed modulation formats. In this paper, the compensation of nonlinear phase noise by a midlink optical phase conjugation (OPC) is studied. A proof-of-principle experiment is presented showing an over 4-dB improvement in Q factor when OPC is employed in a differential phase-shift-keying (DPSK) system. Also, an ultra long-haul OPC-based differential quadrature phase-shift-keying (DQPSK) transmission experiment is studied to show the impact of self-phase modulation (SPM)-induced impairments, including nonlinear phase noise, in a transmission line. OPC results in a 44% increase in transmission distance when compared to a "conventional" transmission system using dispersion compensating fiber (DCF) for chromatic dispersion compensation.     

Structure of light beams in self-pumped four-wave mixing geometries for phase conjugation and mutual conjugation

A family of self-pumped four-wave mixing-based geometries for conjugation and mutual conjugation of light beams is analyzed in the framework of a three-dimensional theory. Results of an experimental investigation of several such geometries conducted with the aim of verification of this theory's predictions are presented. A correspondence between the three-dimensional theory and a more simplistic (but widely used) one-dimensional theory is established.     

基于光学相位共轭的数字化波前整形技术（特邀）

光在生物组织中传播时,会被微观尺度上不均匀的组织随机散射,这种现象严重制约了光学技术在生物医学中的应用。波前整形技术将散射过程当成一个确定性的过程,通过测量散射效应造成的相位延迟并利用空间光调制器进行逐点补偿,可以实现散射光的操控与重新聚焦。在各类波前整形技术中,基于光学相位共轭的数字化波前整形技术具有可调控自由度高、系统响应速度快等优点,最适宜与生物医学应用相结合,如生物活体成像、操控、治疗等。文中将重点关注基于光学相位共轭的数字化波前整形技术的发展,探讨该技术在应用研发中面临的主要技术瓶颈和挑战,并概述其应用开展情况。     

热光非定域螺旋相衬成像（特邀）

边缘增强作为一种图像处理技术,对于研究物体边界信息有着重要的应用。根据热光鬼成像的关联机制,将鬼成像与螺旋相衬成像技术相结合,把相位物体与涡旋滤光器非定域地放在热光鬼成像系统的探测光路和参考光路中,建立了相位物体边缘增强识别系统。实验结果表明,采用具有分数阶轨道角动量拓扑荷的涡旋滤波器可以实现轨道角动量值在0~1范围内的相位物体的边缘渐变性增强效果。随着轨道角动量拓扑荷数的增加,相位物体的边缘增强效果会越明显。非定域螺旋相衬成像相较于传统的螺旋相衬成像方案,突破了被测物体和涡旋滤波器在同一光路,并且滤波器必须放置在频谱面的空间局域性限制,解除了对主动照明光源相干性的要求,增强了涡旋滤波相衬成像系统的泛化能力。     

Optical phase modulators for MHz and GHz modulation in silicon-on-insulator (SOI)

This paper reports the simulation of the direct current (dc), transient, and optical characteristics of low-loss single-mode optical phase modulators based on silicon-on-insulator (SOI) material. The devices operate by injecting free carriers to change the refractive index in the guiding region and have been modeled using the two-dimensional (2-D) device simulation package SILVACO and the optical simulator BeamPROP to determine their electrical and optical performance, respectively. These simulators have been employed to optimize the overlap between the injected free carriers in the intrinsic region and the propagating optical mode. Attention has been paid to both the steady state and transient properties of the device. In order to produce quantitative results, a particular p-i-n device geometry has been employed in the study, but the trends in the results are sufficiently general to be of help in the design of many modulator geometries. The specific example devices used are designed to support a single optical guided mode and are of approximately 1 mm in cross-sectional dimensions. The modeling results predict that the transient performance of the device is affected significantly by the contact width and the rib doping depth. Results presented encompass Gaussian and constant doping profiles in the n/sup +/ regions. The doping profile of the contacts has a tremendous effect on both the dc and transient performances. Phase modulators with drive currents as low as 0.5 mA and transient rise times of 0.3 ns and fall times of 0.12 ns are predicted. Following from these results, a realistic doping profile is proposed that surpasses the electrical results of the Gaussian and most of the constant doping profiles. The improvements in electrical device characteristics are at the expense of a slightly increased optical absorption loss. An alternative switching technique is also presented that could further improve the device speed.     

面光源在皮肤组织中传输的蒙特卡罗模拟计算

光在生物组织中的传输可用蒙特卡罗模拟来计算,但多数局限于对线光源垂直入射的模拟。在实际的使用中,入射光源的形状、大小、光强分布和会聚情况对生物组织内的光传输均有影响。本文以最简单的强度均匀分布的圆形面光源（平圆光源）和实际使用中最具代表性的强度成高斯分布的面光源（高斯光源）为例,讨论光束的大小,强度分布和聚焦情况对生物组织内光能量分布的影响。     

Optical fiber vibration sensor using (Pancharatnam) phase stepinterferometry

A fiber-optic vibration sensor based on polarization and phase-step interferometry is reported. Left- and right-circularly polarized light coming back from the reference and signal arms of a modified Michelson fiber interferometer is processed with an array of five linear analyzers separated angular steps of π/4 (rad) from each other. Thus, five interference patterns are acquired simultaneously and the dynamical phase retrieval problem is reduced to five-step interferometry in the time-domain. A vibration sensor as described above was built by the authors and its performance was investigated     

Optical performance of efficient blue/near UV nitropyridine-conjugated anthracene (NAMA) based light emitting diode

9-[(5-nitropyridin-2-aminoethyl) iminiomethyl]-anthracene (NAMA) was synthesized for the first time from the reaction between 9-antracene carboxaldehyde and 2-(2-aminoethylamino)-5-nitropyridine under mild reaction conditions. The structure of the nitropyridine-conjugated anthracene (NAMA) was characterized using ¹H-NMR, ¹³C-NMR and elemental analysis techniques. Furthermore, electroluminescent behavior of the NAMA was investigated by using a material based on polycyclic aromatic hydrocarbons (PAHs) in organic light-emitting diodes (OLEDs). It was observed that the NAMA exhibits blue/near UV emission at 410 nm with a high density signal. The optimized device structure, ITO/CuPc/α−NPD/NAMA/Alq₃/LiF/Al is characterized by blue/near UV electroluminescence (EL) and a high current density with 7735 cd m⁻² maximum brightness at approximately 10.4 V. The emitting color of the device showed the blue/near UV emission (x, y) = (0.14, 0.10) at 277.1 mA cm⁻² in CIE (Commission Internationale de l’Eclairage) chromaticity coordinates with a long operational lifetime (180 h).     

Colour sensor for (bio)chemical/biological discrimination and detection

Life science is a field of dynamic development and can benefit from the usage of microelectronics in numerous applications. Various devices for separation of different (bio)chemical components from a mixture could be miniaturized in silicon, but they need detectors at their output to identify and characterize the separated elements.The colour sensor is such a detector, and it was preferred because other classical approaches typically used in chemistry or biology employ IR or UV-based analysis, for which it is more difficult to design, optimize and fabricate a silicon-based sensor.Unlike classical detection (using three different filters placed on separate detectors) the proposed device is based on an entirely different approach, using vertically stacked detectors within a single structure that can be fabricated using CMOS-compatible processing.The main requirements for the design of such a vertically stacked multi-junction structure are presented, together with details regarding the most critical processing steps and process parameter values obtained after simulation which were used in the manufacturing of the first version of the device, including some optical design aspects.     

Neural networks application for OPC (optical proximity correction) in mask making

In this paper a neural network method for optical proximity correction is presented. A non linear two-dimensional spatial inverse filter is proposed as deconvolutional factor over pattern plane. Test sets for the different correction strategies were prepared. Boltzmann machine neural network for training set preparation is proposed. For actual correction optimal autoassociative neural network configuration have been chosen. This strategy also opens the way to use a sub-resolution, non-printable correction structures. Additionally, such a system is available for interfacing with next step of correction - for electron proximity effects. Possibility of merging them in one unit were investigated. Some initial results concerning one step OPC and EPC (electron proximity correction) neurocorrector are presented. Different aggressiveness of the correction can be chosen straightforwardly by simple change of the correction kernels in neurocorrector. There is no structural difference of neurocorrector for attenuated, sized rim, Levenson's, outrigger or chromeless methods, thought different attitudes towards training tests generation have to be applied. Both, feature biasing and feature assisted techniques were investigated. Some attempts to quasi-analytical representation of the correction kernel to minimise or even avoid learning process is also presented. For the full power of artificial neural networks to be exploited from hardware implementation rather, initial considerations on VLSI architecture of the neurocorrector are also included.     

用于细胞及组织培养的低强度LED生物光源

研制出可用于细胞及组织培养的低强度发光二极管光源。介绍了此光源的光路原理和简要结构，测试了该光源的辐射照度及其强度分布，使用统计分析软件SPSS拟合得到该光源的辐射照度经验公式。     

A study of the three-dimensional distribution of light (632.8 nm) in tissue

Effective application of photodynamic therapy requires that light dose to tissue be accurately calculated. Special fiber optic detectors have been constructed, and experimental methods developed, for determining three-dimensional flux patterns of red light instilled into tissue. These methods utilize the insertion and movement of the detecting fibers along fixed coordinates within tissue, and the measurement of light flux values at these positions. Resulting values of bovine skeletal muscle have been interpolated and mapped into two-dimensional graphical patterns. Combinations of two-dimensional patterns allow a reconstruction in three dimensions. Either calculation or geometric construction provides penetration depths. Light dispersion is spherically symmetrical, as predicted by diffusion theory. Penetration depths for bovine muscle ranged from 1.8 to 2.3 mm. Three theoretical formulations were fit to the experimental data and were found to be equally valid at depth.     

Zn doping of InP, InAsP/InP, and InAsP/InGaAs heterostructures through metalorganic vapor phase diffusion (MOVPD)

Zinc incorporation by post-growth metalorganic vapor phase diffusion (MOVPD) is used to achieve high p-doping, which is desirable for the fabrication of photodiodes. Diethylzinc (DEZ) is used as precursor and Zn is diffused into InP and InAs_0.6P epitaxial layers grown by low pressure metalorganic vapor phase epitaxy (MOVPE) on different substrate orientations, enabling the investigation of the dislocation density on the Zn incorporation. Diffusion depths are measured using cleave-and-stain techniques, resistivity measurements, electrochemical profiling, and secondary ion mass spectroscopy. High hole concentrations of, respectively, 1.7 10¹⁹ and 6 10¹⁸ cm⁻³, are obtained for, respectively, InAs_0.60P and InP. The diffusion coefficients are derived and the Zn diffusion is used for the fabrication of lattice-mismatched planar PIN InAsP/InGaAs photodiodes.     

Optical properties of (001) GaN/AlN quantum wells

The absorption coefficient and the photoluminescence of (001) GaN/AlN quantum wells are calculated for several values of the well width, with and without the excitonic effect corrections, in the usual monoelectronic approach and as a many-body problem. The calculation was performed considering separate isolated bands for electrons, heavy and light holes. The monoelectronic approach to the optical properties was performed by assuming infinite well walls and finite well walls, respectively. The calculation including the excitonic effect as a many-body problem was performed within a recent approach designed for low-dimensional systems. The different wells studied here present many localized states and a complicated absorption spectrum. The monoelectronic approach in the infinite quantum well approximation reproduces quite well the spectrum of the wide wells due to the fact that the ground states of electrons and holes are well fixed by this model of quantum well.     

Optical clock recovery methods: Review (Invited)

Clock recovery is a fundamental operation in digital telecommunications systems, where the receiver synchronizes itself to the transmitter timing. In optical clock recovery, this operation is made using optical signal processing methods. This paper reviews the physical principles and classifies the various optical clock recovery methods developed during the last 20 years.     

Optical Properties of GaN/SiC/por-Si/Si(111) Hybrid Heterostructures

Semiconductors - Using a complex of structural and spectroscopic methods of diagnostics, the influence of a nanoporous-silicon (por-Si) transition layer on the optical properties of GaN layers...     

Symmetric Versus Unsymmetric Platinum(II) Bis(aryleneethynylene)s with Distinct Electronic Structures for Optical Power Limiting/Optical Transparency Trade‐off Optimization

A new series of symmetric and unsymmetric Pt(II) bis(acetylide) complexes of the type D? C≡C? Pt(PBu₃)₂? C≡C? D (D? Pt? D), A? C≡C? Pt(PBu₃)₂? C≡C? A (A? Pt? A) and D? C≡C? Pt(PBu₃)₂? C≡C? A (D? Pt? A) (D, donor groups; A, acceptor groups) are synthesized, and show superior optical power limiting (OPL)/optical transparency trade‐offs. By tailoring the electronic properties of the aryleneethynylene group, distinct electronic structures for these metalated complexes can be obtained, which significantly affect their photophysical behavior and OPL properties for a nanosecond laser pulse at 532 nm. Electronic influence of the ligand type and the molecular symmetry of metal group on the optical transparency/nonlinearity optimization is thoroughly elucidated. Generally, aryleneethynylene ligands with π electron‐accepting nature will effectively enhance the harvesting efficiency of the triplet excited states. The ligand variation to the OPL strength of these Pt(II) compounds follows the order: D? Pt? D > D? Pt? A > A? Pt? A. These results could be attributed to the distinctive excited state character induced by their different electronic structures, on the basis of the data from both photophysical studies and theoretical calculations. All of the complexes show very good optical transparencies in the visible‐light region and exhibit excellent OPL responses with very impressive figure of merit σ_ex/σ_o values (up to 17), which remarkably outweigh those of state‐of‐the‐art reverse saturable absorption dyes such as C₆₀ and metallophthalocyanines with very poor transparencies. Their lower optical‐limiting thresholds (0.05 J cm^?2 at 92% linear transmittance) compared with that of the best materials (ca. 0.07 J cm^?2 for InPc and PbPc dyes) currently in use will render these highly transparent materials promising candidates for practical OPL devices for the protection of human eyes and other delicate electro‐optic sensors.     

全息聚合材料PQ/PMMA的光学反应分析

为了探究掺杂有菲醌的聚甲基丙烯酸甲酯(PQ/PMMA)光致聚合材料的光学特性,根据该全息聚合材料基本理论以及内部的光化学反应机制与效应,通过数学方法构建内部反应模型进行仿真与拟合,分析了曝光强度、空间频率对产物、折射指数的影响以及存在的失真效应.结果表明:在给定参数下,曝光强度的最佳选择范围为60～80 mW/cm2,空间频率的相对优化的选择为1 800 lines/mm.     

A multi-relaxation (FD)2-TD method for modelingdispersion in biological tissues

Pulse excitation in FD-TD provides multifrequency results with a single run of the code. The introduction of the Frequency Dependent FD-TD ((FD)²-TD) has also recently provided a means to deal with dispersive materials on condition that they had a first order permittivity. The authors present a multirelaxation approach to widen the (FD)²TD applicability to materials with more complex permittivity such as biological tissues