共查询到20条相似文献,搜索用时 109 毫秒
1.
利用光栅进行相衬观察位相物体,光栅作为分束器获得双光束,将双光束干涉条纹调制在位相连续变化的物体上可以支位相物体的折射率进行定量测量。采用编码非相干光源抑制相干噪音,使输出图像更为清晰。 相似文献
2.
建立了由掺Yb光纤激光器阵列、变换透镜、闪耀光栅和输出耦合镜组成的光束谱合成系统的光束传输模型.在考虑光栅角色散、光栅刻槽倾角误差和光栅衍射效率情况下,利用光线追迹法、衍射积分方法、光束非相干叠加原理和强度二阶矩方法,推导出高斯光束非平行倾斜入射到闪耀光栅的相位变化公式以及谱合成光束的光强分布解析表达式.分析了高斯光束非平行倾斜入射到光栅后,光栅角色散、光栅衍射效率和光栅刻槽倾角误差对掺Yb光纤激光器谱合成系统输出光束特性的影响.研究结果表明,谱合成光束具有与单根光纤激光器几乎相同的光束质量;光栅角色散对合成光束特性的影响可忽略;随着光栅刻槽倾角误差的增大,谱合成光束的光束质量明显变差;当光栅刻槽倾角误差较大时,必须考虑光栅衍射效率对合成光束特性的影响.
关键词:
掺Yb光纤激光器
非平行倾斜入射
光束谱合成
光束质量 相似文献
3.
4.
5.
《光学学报》2010,(10)
主动相位控制的光纤激光阵列相干合成在提高输出功率的同时能够保证良好的光束质量,其关键技术在于光纤激光相干阵列的锁相控制。基于随机并行梯度下降(SPGD)算法的锁相控制方案不仅具有控制策略简单、系统结构紧凑的优点,而且通过算法性能评价函数和迭代参数的选取,能够对光纤激光相干阵列进行多种锁相控制,从而得到各种形式的阵列合成光束输出,实现与自适应光子锁相元件整列(APPLE)系统阵列的有效契合。理论研究并实验实现了基于SPGD算法的相位控制方案的同相相干合成锁相控制、合成光束主极大偏转控制和空心光束产生等功能,验证了基于SPGD算法的全电光束控制在各种形态光束控制中的可行性。 相似文献
6.
介绍了本课题组近年来在基于空间结构内部锁相的光纤激光相干合成方面的研究工作,给出了空间结构内部锁相相干合成的基本原理,搭建了七路低功率光纤激光阵列实验系统,结果表明在内部相位噪声校正基础之上,可以稳定补偿外部相位差进而实现激光阵列同相位输出,验证了内部锁相方法的可行性。进一步介绍了空间结构内部锁相技术在目标在回路相干合成、阵列光束光场调控等方面的拓展应用,通过实验论证了空间结构内部锁相技术能够有效提升目标在回路相干合成系统的相位控制带宽,并在远场有效生成轨道角动量光束阵列,其拓扑荷数可从-1到+1切换。 相似文献
7.
8.
9.
10.
建立了光束谱合成的传输模型.应用光线追迹方法,将闪耀光栅引起的相位变化用槽间光程差和槽内光程差来表示,建立了光束倾斜入射到光栅时相位变化的计算模型.利用衍射积分方法,给出了阵列光源各子光束经谱合成系统后输出光场的解析表达式.依据光束非相干叠加的原理,计算得到合成光束的光强分布.在此基础上,利用强度二阶矩方法,分别计算了阵列光束和合成光束的M2因子,并定量分析了谱合成系统参数对合成光束特性的影响.研究结果表明:通过谱合成系统合成光束的M2关键词:
光束谱合成
阵列光源
闪耀光栅
光束质量 相似文献
11.
Bloom G Larat C Lallier E Lehoucq G Bansropun S Lee-Bouhours MS Loiseaux B Carras M Marcadet X Lucas-Leclin G Georges P 《Optics letters》2011,36(19):3810-3812
An external cavity using a binary phase grating has been developed to achieve coherent combining of five quantum-cascade lasers emitting at 4.65 μm. The grating phase profile is designed to combine five beams of equal intensities into a single beam with a good efficiency (~75%). The performances of this cavity concerning output power, stability, combining efficiency and beam quality are detailed. We report a CW combining efficiency of 66% corresponding to an output power of ~0.5 W with a good beam quality (M(2)<1.6). 相似文献
12.
Peter Kozma Andras Hamori Kaspar Cottier Sandor Kurunczi Robert Horvath 《Applied physics. B, Lasers and optics》2009,97(1):5-8
An interferometric sensor based on gratings on a planar waveguide is introduced. The device combines the advantages of known
interference-based waveguide sensors with the simplicity of grating couplers. In the presented configuration, two parallel
and coherent light beams, laterally separated in the direction of mode propagation, are coupled into a planar waveguide through
a grating. One of the coupled beams is phase modulated using a periodically relaxing liquid crystal modulator, resulting in
a time varying intensity signal at the end face of the waveguide. Refractive index changes within the waveguide section between
the two coupling regions are monitored by observing characteristic changes in the intensity signal. 相似文献
13.
We propose a simple method for measuring the gain coefficient of two-beam coupling for photorefractive polymer film. To measure the gain coefficient, we attached a phase grating onto the photorefractive polymer film and made an interference pattern between the transmitted and diffracted beams in the photorefractive film by using an illuminating single beam. The gain coefficient values measured at various external fields by our method showed good agreement with those measured by a standard two-beam coupling method. Compared to standard two-beam coupling, this method exhibited fairly improved stability of the output signal to external factors such as human sounds and airstreams. 相似文献
14.
A scheme for beam combination at any angles employing a specially designed multilayer grating is proposed.Such a grating is able to convert noncoaxial laser beams to coaxial ones, and the combined beams are able to output along the normal line of the grating. The intensity and the phase structure of combined beams can also be controlled. The experiments are carried out by loading an encoded grating on a liquid-crystal spatial light modulator. The results agree well with the simulations. This method of beam combination with a multilayer grating serves to simplify the complexity of beam combination. 相似文献
15.
甲基紫掺杂聚乙烯醇薄膜材料在两束相干光照射下生成相位光栅.当改变一束相干光光程,通过监测相位光栅的一级衍射信号强度的变化,可以检测相位光栅的生长和擦除过程.在此实验基础上,讨论了甲基紫掺杂聚乙烯醇薄膜材料多重全息存储的原理与结果. 相似文献
16.
We study theoretically the fidelities of output coherent images in incoherent-to-coherent conversion based on photorefractive two-wave mixing in the presence of an incoherent image-bearing beam. A vector version of the whole beam split step method is developed. The dependencies of the fidelities of output coherent images on geometric and physical parameters such as the incident direction of the beams, the intensity ratios between the beams, and coupling coefficients are investigated in detail. PACS 42.65.Hw 相似文献
17.
18.
N. M. Kozhevnikov 《Optics and Spectroscopy》2016,120(3):461-464
A method for the measurement of the recording/erasing time of dynamic phase gratings that are recorded by phase-modulated beams in photorefractive medium with local response is presented. The method is based on the detection of the intensity modulation of output beams in the course of rerecording of the grating after a shift of the interference pattern by one-half of spatial period. It is demonstrated that a relatively high sensitivity of the method is due to the selective detection of signals at a high frequency and a high efficiency of energy exchange of the recording beams in comparison with the diffraction of the probe beam. The application of the method in dynamic holographic seismographs is discussed. 相似文献
19.
The characteristics of coherent coupling in Mach-Zehnder erbium-doped fiber laser cavity are experimentally studied. By virtue of a seemly controlling of length difference between two interferometric arms, the obtained comb-like spectrum of interferometer resonator with a period of 0.06 nm commendably agrees with the theory of self-organization coherence. The coherent output exits from the output mirror of a fiber Bragg grating with 4.5% reflectivity. A high coherent combining efficiency of 94% is obtained. Investigation on characteristics of the leak power opens out self-organization mechanism in Mach-Zehnder composite cavity. 相似文献
20.
Oscillatory mode coupling between two coherent laser beams is produced when an interference pattern moves against a quasi-static electrically strobed grating in a photorefractive AlGaAs/GaAs multiple-quantum-well diode operated in the quantum-confined Stark geometry. The oscillation frequency is equal to the frequency difference between the two laser beams and provides a method to measure high-frequency Doppler shifts or large surface displacements for laser-based ultrasound. Combined photorefractive gains (normally forbidden by symmetry in the Stark geometry) and absorptive gains approach 1200cm(-1)during two-wave mixing using moving gratings. 相似文献