Hybrid multinary modulation using a phase modulating spatial light modulator and a low-pass spatial filter

We propose a method for performing binary intensity and continuous phase modulation of beams with a spatial light modulator (SLM) and a low-pass spatial filtering 4-f system. With our method it is possible to avoid the use of phase masks in holographic data storage systems or to enhance the phase encoding of the SLM by making it capable of binary amplitude modulation. The data storage capabilities and the limitations of the method are studied.     

Universal generation of higher-order multiringed Laguerre-Gaussian beams by using a spatial light modulator

Laguerre-Gaussian (LG) beams of various higher-order radial modes are generated by using a reflective phase-only liquid crystal on silicon (LCOS) spatial light modulator (SLM). Because of the LCOS SLM's phase-modulation characteristic of a wide spatial bandwidth, a phase modulation scheme effectively generates higher-order LG beams of up to the fifth-order radial mode. We also perform correlation analyses between the observed and the theoretical two-dimensional mode profiles to universally obtain correlation coefficients of more than 0.946, which suggest mode generations of high quality.     

Spatial mode control of a diode-pumped Nd:YAG laser by an intracavity liquid-crystal light valve

We present a new beam-shaping technique with an intracavity optically addressed liquid-crystal spatial light modulator. The Nd:YAG resonator is able to deliver beams with various spatial profiles such as flat-topped super-Gaussian and square-shaped beams.     

Generation of vector beam with space-variant distribution of both polarization and phase

We present an idea to generate an arbitrary space-variant vector beam with structured polarization and phase distributions. The vector beams are synthesized from the left- and right-hand polarized light, each carrying different phase distributions. Both the phase and the state of polarization of vector beams can be tailored independently and dynamically by a spatial light modulator.     

基于激光光束轨道角动量的8位数据信号产生与检测的实验研究

本文研究了利用激光光束的轨道角动量进行8位数据信息传输的技术. 建立了一套利用光束轨道角动量进行8位数据信息传输的系统, 在信息调制部分采用可选通控制的光源阵列和相位调制屏实现光束轨道角动量态的编码复用, 在信息解调部分采用二元振幅光栅进行轨道角动量态检测,实现了无误码的数据信息传输.     

Quantum key distribution with bright entangled beams

We suggest a quantum cryptographic scheme using continuous EPR-like correlations of bright optical beams. For binary key encoding, the continuous information is discretized in a novel way by associating a respective measurement, amplitude, or phase, with a bit value "1" or "0." The secure key distribution is guaranteed by the quantum correlations. No predetermined information is sent through the quantum channel contributing to the security of the system.     

Special phase mask and related data format for page-based holographic data storage systems

Random phase masks in object and reference beam of page-based holographic storage systems suppress the DC-peak and improve the overlap of both beams inside the storage material. Furthermore, they allow for a narrow shift-selectivity. In a holographic setup the phase mask has to be introduced at a conjugate image plane of the spatial light modulator (SLM), if it is not fixed directly on the SLM itself. A binary phase mask with cells generating 0 and π phase shifts has to be aligned very accurately with respect to the SLM pixels, otherwise image artifacts disturb the received data page. We present a phase mask, where the phase cells have the size of a data block which consists of a rectangular set of SLM pixels. Additionally, the corresponding data page has no data at the position of phase jumps and thus relaxes the alignment tolerance significantly.     

Entangled double-helix phase

We present a novel phase with an entangled double-helix structure. Beams with this phase have the same transverse patterns as those of interference between two doughnut beams. This proposed method allows a complete set of the superpositions of the doughnut modes or the orbital angular momentum states with different topological orders to be obtained. Furthermore, it introduces a simple continuous and controlled rotation of the transverse patterns by use of a spatial light modulator. It can be used to form a three-dimensional structure by three-dimensional trapping in an optical tweezers setup or to study the quantum characteristics of an optical vortex.     

高阶涡旋光束生成技术研究

应用液晶空间光调制器加载螺旋相位片的方法可以高效地生成涡旋光束,但由于液晶空间光调制器分辨率有限,在加载高阶螺旋相位片时其中心会出现相位失真,造成涡旋光束质量不高。通过在螺线相位片中心区域引入闪耀光栅的方法,得到了光束质量较高的高阶单模涡旋光束和多模涡旋光束,为生成高阶涡旋光束提供了一种很好的方法。     

Coherent Beam Combination of Two Polarization Maintaining Ytterbium Fibre Amplifiers

We investigate coherent beam combination of fibre laser beams by phase locking. Phase noise of a polarization maintaining ytterbium fibre amplifier is inspected with a fibre interferometer. In a feed back control loop, two fibre polarization maintaining ytterbium amplifiers are phase locked and coherent combined when the phase noise is properly controlled by a LiNO3 phase modulator.     

Phase-shifted Fresnel axicon

We propose an optical element: a phase-shifted Fresnel axicon for generation of multiple Bessel beams. By giving a binary phase modulation to the standard Fresnel axicon, the proposed element is generated. The phase profile of the binary phase modulation is engineered to generate two and three Bessel beams of equal intensities. This composite optical element is fabricated using electron beam direct writing. The performance of the fabricated device is evaluated using a semiconductor laser, and the generation of two and three Bessel beams is successfully demonstrated.     

Parallel two-photon photopolymerization of microgear patterns

We report parallel two-photon photopolymerization of microgear patterns by exposing a photoresist to holographically generated optical vortices. The optical vortices are created by imparting a helical pitch onto the incident light using a programmable lithographic phase mask realized with a computer addressable phase-only spatial light modulator. By varying the phase levels of the spatial light modulator, the truncated helical phase of an optical vortex results in output intensity patterns that typifies that of microgears instead of perfect doughnut beams. Our experiments and simulations are in good agreement implying a more efficient and highly parallel two-photon photopolymerization scheme that can be subsequently used for non-scanning fabrication of microgears.     

Direct current balancing algorithm for FLCOS binary phase holograms

The need for DC balancing phase pixels in ferroelectric liquid-crystal-on-silicon spatial light modulators leads to control schemes that limit their use in beam steering applications where a continuous display of a routing hologram is required. By analyzing the phase redundancy in binary phase holograms, a new DC balancing algorithm has been developed that allows more general beam splitting and multiple beam steering functions. The theoretical derivation of the algorithm and experimentally measured properties of the optical beams are presented and discussed.     

Sorting and detecting orbital angular momentum states by using a Dove prism embedded Mach-Zehnder interferometer and amplitude gratings

An experimental system consisting of a Dove prism embedded Mach-Zehnder (M-Z) interferometer and two gratings was built to sort and detect orbital angular momentum (OAM) states of light beams. The helical beams with different OAM states were generated by propagating the fundamental-mode Gaussian beam through a spatial light modulator. The Dove prism embedded M-Z interferometer was used to sort helical beams with odd or even OAM number and two binary amplitude gratings were used to measure the OAM states. Sorting of coaxially-superposed coherent and incoherent helical beams with odd and even OAM states was realized in the experiment.     

Common-path interferometry with one-dimensional periodic filters

We discuss a spatial filtering interferometry setup that employs a periodic spatial filter with either cosine transmittance or binary phase modulation. The setup's input plane is formed by two separate windows, one of which supports a phase object and the other, a reference beam. Using the appropriate frequency and orientation of the filter produces an interference pattern of the two input fields at the output plane of the system. The main attributes and advantages of the setup are discussed and experimentally illustrated with the example of a binary phase periodic filter implemented with a spatial light modulator.     

用于原子干涉仪的拉曼光的制备

原子干涉仪是利用原子物质波的特性而实现的干涉仪,广泛应用于精密测量领域.在原子干涉仪中,通过拉曼光对原子进行相干操作,拉曼光的质量直接影响着干涉仪的技术指标.基于注入锁定技术,采用普通半导体激光器、声光调制器,实现了功率、频率和位相稳定的拉曼光的制备,并对拉曼光的相位噪声技术指标进行了测试.     

白光在LiNbO3∶Fe晶体中写入的任意折射率分布光波导

在理论分析LiNbO3∶Fe晶体中光致折射率变化分布与写入光的强度分布之间关系的基础上，提出了一种在该晶体中写入具有任意折射率分布光波导的新方法.利用由白光经电寻址空间光调制器得到的强度分布不同的片光辐照晶体，分别写入了折射率呈误差函数分布和平方律分布的光波导结构.采用干涉法测量了晶体中的光致折射率变化，并用推导出的折射率变化分布解析表达式很好地拟合了测量数据.实验结果表明，该方法是可行的.利用白光光源结合高分辨率的空间光调制器有望在多种光折变材料中制备出具有任意折射率分布的高质量光波导.     

白光在LiNbO_3∶Fe晶体中写入的任意折射率分布光波导

在理论分析Li NbO3∶Fe晶体中光致折射率变化分布与写入光的强度分布之间关系的基础上,提出了一种在该晶体中写入具有任意折射率分布光波导的新方法.利用由白光经电寻址空间光调制器得到的强度分布不同的片光辐照晶体,分别写入了折射率呈误差函数分布和平方律分布的光波导结构.采用干涉法测量了晶体中的光致折射率变化,并用推导出的折射率变化分布解析表达式很好地拟合了测量数据.实验结果表明,该方法是可行的.利用白光光源结合高分辨率的空间光调制器有望在多种光折变材料中制备出具有任意折射率分布的高质量光波导.     

可操控二种冷原子或冷分子样品的光学双阱新方案及其实验研究

提出了一种构建可囚禁与操控二种冷原子或冷分子样品的光学双阱的新方案,该方案采用常用的液晶空间光调制器作为分光器件,分光调制函数类似二元相位光栅;对提出的方案进行了模拟实验研究,并研究了从光学双阱到单阱的双向演化过程,该光学双阱的模拟实验结果表明与理论方案相符,双阱的操控性好,有利于二种不同的冷原子或冷分子样品的装载与操控等相关实验研究. 关键词： 原子光学 原子分子囚禁 液晶空间光相位调制器 光学双阱     

Phase gratings to couple several input beams into one output beam

Phase gratings with certain continuous grating profiles are shown to be excellent devices for beam coupling, that means to couple N input beams into a single output beam. These gratings are also known as N-to-one-interconnection gratings. We prove in this paper that if the relative phases of the incoming beams are chosen properly coupling efficiencies over 90% are achieved. Only thin phase-only gratings are considered. The input angles of the incoming waves may be freely chosen. The effects of noise in phases and in grating profiles are also numerically calculated and discussed.