Improved optical performance of the Radon-Wigner display for one-dimensional signals

An improved optical implementation of the Radon-Wigner display for one-dimensional signals based on fractional Fourier transform is proposed. All of the fractional Fourier transform orders with the correct magnification can be achieved simultaneously by the suggested new setup with high precision, which consists of only two optical elements, a cemented linear varifocal lenses and a curvy image plane. This setup can offer practical applications for analyzing and processing of stationary or non-stationary signals.     

Optical implementations of the Radon-Wigner display for one-dimensional signals

New optical implementations of the Radon-Wigner display for a one-dimensional signal are proposed based on the fractional Fourier transform. The setups involve only one varifocal lens. Furthermore, the same magnification can be realized simultaneously for all the fractional transform orders, which is quite convenient for practical applications.     

Pulse propagation analysis based on the temporal Radon-Wigner transform

Based on the space-time duality and the temporal imaging theory, an optical implementation of the Radon-Wigner transform in the time domain is proposed for analyzing the propagation of ultrashort light pulses in guided dispersive media. As an application of this approach, we discuss the temporal selfimaging or Talbot effect originated by a periodic pulse train. The frequency chirp of the pulses is also considered in order to evaluate its effect on both the integer and the fractional selfimages.     

Polarization of atoms by simultaneous electromagnetic pulses of different frequency ranges

A method is proposed for the fast and deep polarization of a system of ground-state hyperfine sublevels of an atom having an optical excited level or a system of excited-state sublevels. The method is based on the simultaneous action of pulsed bichromatic resonance fields of optical and microwave ranges. The scheme of the ground-state sublevel polarization by bichromatic or monochromatic microwave fields is also considered.     

Diffractive elements based on spiral beams as devices for determining the depth of bedding of radiation sources

A modified iteration method is proposed for calculations in developing diffraction optical elements for the generation of rotating light fields. The main feature of the proposed approach is the use of the spiral light beam theory for selecting the initial phase approximation. The diffractive optical elements under study could be used in microscopic analysis of the spatial location of different objects.     

Propagation of electric fields induced by optical phonons in semiconductor heterostructures

The penetration of electric fields accompanying long-wavelength optical phonos from one region of a semiconductor heterostructure to another is investigated. It is proposed to determine the penetration depth of such fields from the relaxation caused by these fields in quantum dots. By the example of a cylindrical Ge quantum dot embedded in a GaP/GaAs heterostructure, it is shown that the electric fields induced by longitudinal optical phonons can penetrate through the interface between semiconductors at distances of about 100 nm.     

Generation of Accelerating Beams along Arbitrary Trajectories

A phase superposition approach for generating arbitrarily accelerating beams is proposed, where the superimposed phase is composed of multiple sub‐phases, each of which determines an independent sub‐beam or sub‐trajectory. Further, an effective algorithm is developed to improve the uniformity of the intensity along the arbitrary trajectory by introducing phase‐shift factors. Experimental results are consistent with numerical simulations. The proposed method can be extended to nonparaxial fields, and it also breaks the previous trajectory restrictions. The arbitrarily accelerating optical beams can pave the way for optically moving particles along a predefined trajectory. The property of such beams following arbitrary trajectories is likely to give rise to new applications in wave front control, flexible optical manipulation, and optical transport and guidance of particles.     

基于折射率梯度门限的气动光学窗口光传输研究

基于流场界面厚度（Interfacial—Fluid—Thickness,IFT）理论,建立了高折射率梯度门限模型来研究气动光学窗口光传输畸变。首先在光学窗口折射率梯度场基础上,提出高折射率梯度门限,忽略绝对值低于该门限的折射率梯度值,重构折射率场,并对其气动光学传输效应进行仿真。结果表明,当58．37％的梯度值被忽略时,得到的重构折射率场与原折射率场仿真光程差（OPD）最大相对误差不超过1．5％,验证了气动光学窗口高折射率梯度区域是产生光传输畸变的主要原因,也证实了该门限模型对气动光学窗口光传输效应进行仿真的可行性,对气动光学失真的机理、预测及校正有一定的指导意义。     

Simultaneous Determination of the Amplitude-Phase Structure of an Optical Signal and a Transfer Function with the Influence of the Medium Given by a Modulation Function

We consider a solution to the phase problem in optics as applied to registering and analyzing amplitude-phase structures of 1) d optical fields that form or transfer images and 2) transfer or spread functions of the medium where optically inhomogeneous fields propagate or those of the systems forming fields and producing distortions. The influence of the medium is characterized by the modulation function and is described by the operation of multiplication. In order to measure the amplitude and phase field characteristics and transfer or spread functions, we use an original development of the modulation-spectral method proposed earlier by the authors. There are two variants of optical schemes considered. They include identical parts designed to form the light field to be processed. Using the first optical system, one forms the spectrum of spatial frequencies and introduces the first additional space modulation in the plane of spatial frequencies. The second optical system is placed in the same plane to form the image of the investigated field in the input plane of the developing scheme after passing the transmitting medium. In the first variant, the second part of the scheme contains at the input the third optical system forming the spatial spectrum in the registration plane. At the input of this scheme, the second additional spatial modulation is introduced. In the second variant, the third optical system forms the image of the developing scheme input plane in the registration plane. The second additional spatial modulator is placed in the spatial frequency plane of the third optical system. In the output, in both cases four independent two-dimensional intensity distributions are registered, which allow one to solve the formulated problem.     

A New Simple Ultrahigh Speed Decoding Algorithm for BCH Code

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A New Simple Ultrahigh Speed Decoding Algorithm for BCH Code

In order to content with forward error correction (FEC) technology of the high-speed optical communication system, a new simple decoding algorithm for triple-error correcting Bose, Chaudhuri, and Hocquenghem (BCH) code is proposed. Without complicated matrix-operation or division-operation or intricate iterative algorithm, the algorithm is high efficient and high-speed because of its simplicity in structure. The result of hardware emulation confirms that the algorithm is feasible completely. Introduction of the parallel structure increases the speed of coding greatly. The algorithm can be used in the high-speed optical communication system and other fields.     

基于热膨胀效应的可调光功率分束器设计

可调光功率分束器是集成光子系统中的重要功能器件,其光功率输出具有动态可调控特性,诸多光子系统对其有着广泛需求.本文基于空隙槽型Y分支波导结构,利用热膨胀效应,提出了一种新型可调光功率分束器实现方法,通过调控温度来改变分支处空隙槽的宽度,以实现其分支波导的光功率输出的动态变化.采用有限元方法,对其热膨胀形变和光学性能进行了模拟分析.其模拟结果表明,该器件能实现大范围光分束调控,且对波长和偏振态依赖性低;同时,该器件具有结构简单、易于设计和制作、易于调控等优点,这种新型器件在各种光子系统中具有重要应用前景.     

Entanglement of Coupled Optomechanical Systems Improved by Optical Parametric Amplifiers

A scheme to generate the stationary entanglement of two distant coupled optical cavities placed optical parametric amplifiers is proposed. We study how the optical parametric amplifiers can affect the entanglement behaviors of the movable mirrors and the cavity fields. With the existence of optical parametric amplifiers, we show that larger stationary entanglement of optical and mechanical modes can be obtained and the entanglement increases with the increasing parametric gain. Especially, the degree of entanglement between the two cavity fields is more pronouncedly enhanced. Moreover, for a fixed parametric gain, the entanglement of distant cavity optomechanical systems increases as the input laser power is increased.     

低维半导体异质结中的量子相干红外发射机理理论研究

给出了一种在非粒子反转条件下量子阱和量子点激光器的红外发射机理.此种红外发射是基于在同一作用区产生并作为红外场相干源的两种带间跃迁激光场的共振非线性混合.这种频率下转换机理并不依赖于在半导体激活媒质中的长时相干假定条件,在室温和泵注入电流条件下仍然有效.频率下转换的固有效率可以达到相当于每个可见光子产生一个红外光子的量子极限值.根据红外发射的可参变特性,这种非粒子反转的方法尤其适用于长波红外工作范围.     

Proposals for the generation of angular momentum from non-uniformly polarized beams

Several optical arrangements using non-uniformly polarized fields are proposed for generating beams with spin and/or orbital angular momentum. By choosing adequately the input beam polarization and the characteristics of the different proposed set-ups we can control the overall angular momentum of the output beam at will. The orbital angular momentum is analyzed with the beam moments theory and the spin term is evaluated using the averaged s₃ Stokes parameter.     

光学薄膜自动设计的多目标优化方法

光学薄膜中已使用的优化方法郜是单目标寻优的,通过分析光学薄膜优化设计的原理,将薄膜设计的物理问题归结为混合离散变量的多目标优化设计的数学模型,并认为这是薄膜设计的一般性模型,现行的单目标优化算法只是这个模型的简化.基于这一新思路,并结合多目标优化算法的研究现状,采用了一种基于免疫应答原理的智能型多目标优化算法.该算法隐含并行处理能力,原理上是具备全局搜索能力的自适应随机性算法.将此算法运用到光学薄膜设计中,给出了一些优化的设计实例.结果表明,将多目标优化算法引入薄膜设计的新思路是可行的,将来会有较好的发展前景.     

Effect of metamaterial layer on optical surface plasmon resonance sensor

In this paper an optical surface plasmon resonance (SPR) sensor with metamaterial for four and five layered structure is studied. The numerical results presented in this paper leads to a significant properties of metamaterials in sensing field. Computed results of SPR sensors using metamaterial are compared with conventional optical SPR sensors for four and five layered structure. It is seen that wider dynamic range or effective range of measurable refractive index increases when metamaterial layer is used. It is also verified that SPR sensor with metamaterial layer can dramatically enhance the resolution and reduce the reflectivity compared with conventional SPR. Validity of the magnetic field results is proved on the basis of smooth match of the fields in the different layers of the proposed optical SPR sensor.     

Addressing individual atoms in optical lattices with standing-wave driving fields

A scheme for addressing individual atoms in one- or two-dimensional optical lattices loaded with one atom per site is proposed. The scheme is based on position-dependent atomic population transfer induced by several standing-wave driving fields. This allows various operations important in quantum-information processing, such as manipulation and measurement of any single-atom, two-qubit operations between any pair of adjacent atoms, and patterned loading of the lattice with one atom per every nth site for arbitrary n. The proposed scheme is robust against considerable imperfections and actually within reach of current technology.     

Interferometric methods for suppressing additive noise

Interferometric methods for signal processing, which make it possible to obtain a better noise protection of information laser and optoelectronic systems during detection and processing of optical fields under conditions for external additive noise, are proposed based on the results of analysis of the specific features of field formation in passive and active optical interferometers. The possibility of reducing the effect of external factors on the efficiency of additive-noise suppression by supplementing an interferometer with a stimulated-Brillouin-scattering fiber mirror is investigated. The technical feasibility of the methods proposed is shown and their efficiency is experimentally confirmed.     

A numerical technique for solving the scalar wave equation for Gaussian and smoothed-out profiles

A numerical technique, based on transforming the scalar wave equation to a finite interval before discretization is applied, is proposed for the solution of the scalar wave equation defining the modal fields and propagation constants of optical fibres. It is used to compute the propagation constants and modal fields of weakly guiding fibres of circular cross-section when the refractive index profile has a Gaussian or smoothed-out form. The smoothed-out profiles are studied because they vary continuously from the Gaussian to the step profile. Results are compared with and shown to be accurately approximated by simply explicit functions, dependent only on the fibre parameter.