Polarization phase-shifting Jamin shearing interferometer

The Jamin shearing interferometer is very useful in wavefront testing, especially for the low coherent light. Based on this interferometer, a polarization phase-shifting Jamin shearing interferometer is proposed to improve the performance. In the interferometer, two interference beams are linearly polarized and a polarization phase shifter is applied to realize the phase shifting. Different types of configurations of the interferometer are given. With phase-shifting interferograms, the precision of the interferometer can be improved. The interferometer is kept as an equal optical path system and its shearing amount remains changeable with simple structure and easy operation. In experiments, phase-shifting interferograms are obtained by rotating the analyzer. The usefulness of the interferometer is verified.     

高速转镜干涉成像光谱仪

介绍一种高速转镜干涉光谱仪原理,提出一种基于该原理的干涉成像光谱仪,该成像光谱仪有较大视场角,提高了扫描效率,特点是用带有倾角平面反射镜转动代替传统Michelson干涉成像光谱仪动镜的直线运动,解决了Michelson干涉成像光谱仪扫描效率低和不稳定的难题.     

A displacement measurement system, utilizing a Wollaston interferometer

A dual interferometric displacement measurement system is presented where a Wollaston prism interferometer is employed in conjunction with a normal Michelson interferometer. The system operates without the use of external polarizers, apart from those associated with the Wollaston prism interferometer itself. It is shown that an optical path difference induced in the Michelson interferometer can be detected using the Wollaston prism in a normal interferometer arrangement. Further, the interference pattern produced by the Wollaston prism interferometer changes in a measurable, linear fashion as the optical path difference from the Michelson interferometer alters. A simple theoretical analysis of the system is presented and used to derive a computer model of the optical arrangement. Results from an experimental implementation of the system, using a Wollaston prism with a beam separation of 0.5 degrees and a superluminescent diode, of wavelength 825 nm, as a light source, are included and compared to the results from the computer model.     

Robust one-beam interferometer with phase-delay control

A robust one-beam interferometer with external phase-delay control is described. The device resembles a Mach-Zehnder interferometer in which the two arms are together in one collimated beam. However, the proposed device is not an amplitude-division interferometer but a wave-front division one. The phase-delay control occurs at the interferometer output with the help of two polarizing beam splitters, a quarter-wave plate, a Faraday rotator, and a polarizer. An additional phase delay is introduced by application of an electrical current to the Faraday rotator or by rotation of the polarizer (the latter is of topological origin), which permits the use of techniques of phase-stepping interferometry.     

Compulsorily Phase Locked Interferometer Using Orthogonally Polarized Light Source of a Modulated LD with High Extinction Ratio

This paper describes a compulsorily phase locked differential interferometer using an orthogonally polarized light source of a modulated LD with high extinction ratio to reduce non-linearity of the interferometer caused by polarization cross-talk. The current modulated LD is used as a light source to make the interferometer compact and for the scanning phase of the interferometer. The interferometer is operated compulsorily at the maximum inclination point of the fringe intensity curve by fringe scanning and an electric system. A Wollaston prism of high extinction ratio (50 dB) is used to combine the polarizing beams and to make the polarization cross-talk very small. In one light source the polarized output beams are on the same propagation axis; in the other they have a small crossing angle (2.5 mrad ∼ 10 mrad) to completely exclude non-linearity of the interferometer causded by polarization cross-talk. Using jets of a gas mixture of nitrogen and ethylene, this interferometer was demonstrated to be useful in detecting the photothermal effect of a photothermal velocimeter under phase fluctuation in a turbulent flow.     

Wavelength-Tunable Laser-Diode Interferometer

Laser diodes (LDs) have been applied to a phase-measuring interferometer through the wavelength tunability of LDs by controlling their currents. Laser-diode interferometers based on a heterodyne technique are reviewed. A two-wavelength laser-diode interferometer is demonstrated with current control of dual LDs in opposite directions. A synthetic wavelength makes it possible to extend the range of interferometric measurements. The wavelength is controlled by the laser injection current and is stepwise or rampwise changed to introduce a time-varying phase difference between the two beams of an interferometer with unbalanced optical path lengths. The optical output is demodulated with a phase-extraction algorithm. Systematic phase errors caused by the LD-power variation and by the difference between the beat frequency and ramp frequency are analyzed. A feedback interferometer with electronics is used to eliminate the phase error by locking the interferometer on a preset phase. Typical experimental results are shown.     

光纤连接器端面几何参量自动测量仪

报道了一种高精度测量光纤连接器端面几何参量的自动测量仪。叙述了光纤连接器的端面几何参量的测量原理。由光纤连接器端面形貌和纤芯中心坐标,可以高精度得到曲率半径、顶点偏移量、端面倾斜角和光纤高度等影响连接器性能的关键端面几何参量。该仪器体积小,自动化程度高,用户界面友好,使用方便,可测量物理接触、角度式物理接触等类型的光纤连接器端面几何参量。实际测量证明,该测量仪有很好的重复测量精度。该测量仪与美国Dorc公司ZX-1 mini PMS测量仪和Norland公司NC3000测量仪相比,测量精度水平相当。该仪器样机已通过华东国家计量测试中心的测试。     

Dispersive white-light spectral two-beam interference under general measurement conditions

Spectral-domain interference of two beams from a white-light source is analysed theoretically and experimentally when the effects of both dispersion in an interferometer and the response function of a spectrometer are taken into account. The spectral interference law is expressed analytically under the condition of a Gaussian response function of a spectrometer. The theoretical analysis is accompanied by experiments employing a dispersive Michelson interferometer and a low-resolution spectrometer. Two experiments with different amounts of dispersion in the Michelson interferometer are realized giving rise to the spectral interference fringes resolved only in the vicinity of the so-called equalization wavelength, at which the group optical path difference between interfering beams is zero. The recorded spectral interferograms are in good agreement with the theoretical ones, which are modelled knowing dispersion in the interferometer and the bandpass of the spectrometer.     

Double-grating interferometer with a one-to-one correspondence with a Michelson interferometer

We describe a double-grating interferometer that has a one-to-one correspondence with a Michelson interferometer. The half spatial periods of the gratings are equivalent to the wavelengths of the interferometer. The widths of the interference fringes can be changed easily. The intensity distribution of the interference pattern is independent of the wavelength of the light source used. The surface profile of an object can be measured because two interference beams can coincide precisely on the image plane of the object. The measuring range is much larger than that of a Michelson interferometer.     

Generation of longitudinal modes in an active Fabry-Perot fiber interferometer pumped by a low-power single-frequency semiconductor laser

The results of experiments on taking beat spectra at the exit of a stationary (modulator-free) fiber Mach-Zender interferometer are presented. The interferometer is excited by a single-frequency semicon-ductor laser with an output power varying from 0.65 to 2.00 mV and a line-width of less than 20 kHz. The observed line beat spectrum is explained based on the fact that the extended (several kilometers long) arm of the interferometer serves as an active fiber Fabry-Perot interferometer. In this case, the effects of enhancement of stimulated Mandel’shtam-Brillouin scattering in the fiber and the Fresnel reflection of light from the end faces of the fiber play a decisive role. Remarkably, these effects are observed at a low (less than 0.3 mW) power deposited into the fiber. The features of beat signals are considered, and the feasibility of applying this effect in high-sensitive field and displacement optical sensors is indicated.     

Biprismainterferenzen mit langsamen Elektronen

Diffraction patterns of low energy electrons (150 eV) were observed with an electron interferometer. An interferometer of special design was developed for this purpose. The electron source is reduced in size by a retardation lens, which simultaneously decelerates the electrons down to about 150 eV. The electron beam is split up by an electrostatic biprism (filament diameter 10 μ ¦) in two coherent waves, which recombine behind the biprism giving a Fresnel diffraction pattern. Then the electrons are accelerated and the interference fringes are electron optically magnified. In comparison with an interferometer for high energy electrons the intensity on the viewing screen is higher.     

外差干涉仪中声光调制器特性对测量精度的影响

提出并论证了混合型声光调制器衍射光的衍射级次混叠特性, 它使衍射光强中存在着驱动频率的谐波项, 此外入射光束的漂移将引起衍射光的频率漂移。分析了在外差干涉仪中应用它们对测量精度的影响, 提出了消除这些因素影响的方法： 利用双声光调制器外差干涉, 并在干涉仪的内部提取测量的参考信号。用双声光调制器的外差干涉仪可以实现纳米测量。     

Time-resolved spectral analysis of transient processes in Fabry-Perot interferometers

Parameters of a spectrochronograph that represents a Fabry-Perot interferometer combined with a spatial-time analyzer (a streak camera) are analyzed. Using numerical simulation, time scans of interferograms for bandwidth-limited and phase-modulated pulsed optical signals are obtained. The conditions are determined under which a Fabry-Perot interferometer represents a high-accuracy instrument for measuring the timeresolved spectral dynamics of short optical signals. In particular, an adequate representation of relatively smooth and monotone changes in amplitude and phase characteristics of an optical signal in a spectrochronograph requires that the mode lifetime in a Fabry-Perot interferometer be matched to the time scale of changes in the spectral structure of a pulse being studied. The character of distortions formed in the time-resolved spectral patterns in the case where these conditions are not fulfilled is qualitatively determined, and quantitative estimates of the distortions are presented. The results of the analysis and the numerical calculations show that a spectrochronogram obtained using a Fabry-Perot interferometer and a time analyzer (a streak camera) with parameters corresponding to the criteria formulated in the paper enable one to obtain information on the initial amplitude-phase pattern of a light pulse.     

“Compact Spectral Imaging” System Using Liquid Crystal for Fast Measurement

The authors propose a compact system for measuring a multispectral image within a short observation time. This system consists of a lens array and a polarization interferometer. The interferometer has two wedge-shaped liquid crystal layers. Images of an object created by the lens array are modulated with variable optical path differences by the interferometer and detected simultaneously by an image sensor. From the detected images, we can reconstruct the spectral image of the object. Experimental results are presented.     

半导体激光微小振动实时干涉测量仪

设计了一种半导体激光干涉测量仪,可以实时测量物体的微小振动。通过信号处理电路对干涉信号进行分析,得到实际振动的振幅和频率。给出了具体的理论分析,实验结果验证了该干涉仪的实用性。     

All-guided stellar interferometer with an integrated optics recombiner

We report laboratory tests of an all-guided stellar interferometer used for optical aperture synthesis. In anticipation of use of the interferometer in space missions, this research is focused especially on compactness of the recombining device. The coherent transport and delay lines are implemented with polarization-maintaining fiber. Beam recombination is achieved by means of an integrated optics component. This two-arm interferometer operates at 670-nm mean wavelength and allows for a 24-cm correction for the differential air path.     

Submillimeter laser interferometry with pyroelectric image recording

The interferometer with a submillimeter laser and standard pyroelectric TV camera for visualization of interference fringe pattern is described. Problems typical for the development of such interferometer are solved by choosing of a proper arrangement and a mutual spacing of its elements with respect to laser. The interferograms of a teflon wedge and an arcing plasma are presented as an example.     

利用原子干涉仪的相位调制进行绝对转动测量

提出一种基于原子干涉仪的相位调制进行绝对转动测量的方法.以π/2-π-π/2构型的空间型原子干涉仪为例,通过对拉曼激光进行相位调制,然后在动量谱空间测量转动对原子速度谱的调制周期,获得原子干涉仪相对惯性空间的绝对转动.文章对于采用该法进行角速度测量的测量范围以及对相位调制频率的要求进行了分析,对于散粒噪声限下的转动测量灵敏度及其影响因素进行了仿真. 关键词： 原子干涉仪 原子陀螺 相位调制 绝对转动测量     

Ultimate sensitivity of a reflection interferometer with a noninverted instrumental function

Properties of a multiple-beam interferometer with a transmission-like pattern of the fringes in reflected light are considered. A specific feature of this interferometer (a transmission-like reflection interferometer, or TRI) is an asymmetric one-sided mirror with a multilayer dielectric coating and a thin absorbing film. Characteristics of the mirrors and the interferometer as a whole are calculated as functions of the number of dielectric layers. In the calculations, the losses inside the dielectric coating, which are assumed to be concentrated in the vicinity of the layer boundaries, are taken into account. It is shown that a TRI, in terms of its sensitivity, does not differ substantially from conventional multiple-beam interferometers for the same level of technology of the dielectric coatings. The TRI version under consideration demonstrates mode self-filtration, due to which it reflects only the fraction of the incident light corresponding to the resonance of the interferometer. This allows one, in principle, to eliminate special mode cleaners and to significantly simplify the entire optical arrangement.     

High-speed scanning fiber-optic heterodyne interferometer using a micro-electro-mechanical system mirror and an f-theta lens

This paper describes a novel fiber-coupled heterodyne interferometer using a micro-electro-mechanical system (MEMS) mirror and an f-theta lens. In this interferometer system, the cross-polarized laser beams operating at 2 μm with the frequency difference of 100 kHz are introduced by means of the two acousto-optic modulators (AOM). The sample with diameter of 300 mm is uniformly scanned by the 1 mm laser beam with the help of the combined optical scanning configuration, a MEMS mirror and an f-theta lens. The output intermediate signal from the two channels, reference channel and the measurement channel, are processed in the 12 bit analog-to-digital (A/D) process system. Details of our interferometer scheme are discussed.