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.     

What type of coherence of the optical field is observed in the Michelson interferometer

The types and corresponding coherence functions of the optical field are considered depending on the frequency and angular spectra of the field. The main concepts of the theory of coherence effects in the interference experiment with the amplitude splitting of the initial field are discussed. It is shown that, in strict correspondence with the theory of coherence of the random wave fields, the Michelson interferometer reveals manifestations of the transverse and longitudinal spatial (rather than temporal, as it is commonly adopted) coherence of the optical field; the purely temporal coherence of the optical field is revealed only under special conditions of the interference experiment. Beyond these conditions, either spatial or spatiotemporal coherence is revealed.     

极紫外光刻系统物镜光学元件的支撑与分析

介绍了极紫外光刻系统物镜光学元件的支撑原理和支撑要求,分析了符合运动学支撑要求的物镜支撑结构和面形检测用支撑结构;针对支撑结构性能和支撑方案中关键问题进行了深入研究,并提出了相应的解决方案。最后建立了支撑结构的有限元模型,并在此基础上进行了重力场中的镜体变形分析和温度场作用下系统的热变形分析。分析结果表明,检测用支撑与实际用支撑两种结构在重力环境下支撑出的元件面形基本相同,面形相差0.0026nm(RMS);温控范围为0.05℃时,由机械结构热变形引起的镜体面形变化在0.001nm(RMS)量级。研究结果表明,运动学物镜元件支撑结构能够满足极紫外光刻系统对于物镜机械支撑结构的要求。     

Interferometric precision measurements with Bose–Einstein condensate solitons formed by an optical lattice

We propose the precision measurement of both angular rotation and of the gradient magnetic of a field based on the use of matter wave interferometers with soliton states of a Bose-Einstein condensate (BEC). We consider the formation of these soliton states in a BEC with negative scattering length by an optical lattice produced by two counterpropagating laser beams. We determine the parameters of both the initial condensate and the optical radiation necessary for the formation of coherent solitons. We demonstrate that this interferometer can be used to measure magnetic field gradient with a precision of 10^-2 pT/cm. Our calculations show that the sensitivity of a gyroscope based on a ring, two-port matter wave interferometer can achieve 2.6×10^-7 rad s^-1. The precision of this method is more than ten times greater than in that of rotating interferometer with cooled atoms.     

Mechanism of shape formation of optical structures in a nonlinear Fizeau interferometer as the mirror is shifted and the beam dimensions are varied

The article is concerned with the study of shape formation in a nonlinear Fizeau interferometer with two-dimensional feedback. In a preceding study [1], an approach was presented by means of which it is possible to elucidate the mechanism underlying the formation of the simplest optical structures for particular values of the parameters of the interferometer and the input optical beam. In the present article, an attempt is undertaken to account for the production of shear instability type structures and structures that arise as the beam dimensions in the feedback loop are varied. Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 67–72, July, 1997.     

A single-mode-fiber-based point diffraction interferometer

Based on the modification of a point diffraction interferometer, a method for measuring the optical fields from remote objects and external sources is developed. In this method, the reference beam is obtained from the studied beam by filtration of its spatial spectrum with a single-mode optical fiber. To eliminate the effect of phase errors caused by the nonideality of elements of the optical scheme on the measurement results, we developed a procedure of interferometer calibration that permits one to determine these errors with the aim of subtracting them from the measured field phase distributions.     

Mechanism of the formation of static and rotating multilobe structures in a nonlinear Fizeau interferometer

The article considers the formation in a nonlinear Fizeau interferometer with two-dimensional feedback. In a previous paper [1] we proposed an approach that could elucidate the mechanisms of formation of simple optical structures for specific values of the parameters of the interferometer and the input optical beam. In the present paper we try to explain the formation of static and rotating multilobe structures. Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 75–79, April, 1997.     

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.     

高灵敏度的量子迈克耳孙干涉仪

迈克耳孙干涉仪不仅可以用来研究物理学的基本问题,而且能够用于精密测量,比如引力波信号的测量.因此,构建高灵敏度的迈克耳孙干涉仪是实现微弱信号测量的关键.目前,人们利用压缩态可以降低迈克耳孙干涉仪的噪声;通过光学四波混频过程能够放大马赫·曾德尔干涉仪中的相位信号,从而提高干涉仪的信噪比和灵敏度.本文研究了一种用于高灵敏度相位测量的量子迈克耳孙干涉仪.在迈克耳孙干涉仪中,利用非简并光学参量放大器取代干涉仪中的线性光学分束器;并且将压缩态注入干涉仪的真空通道,可以得到高信噪比和高灵敏度的干涉仪.由于存在不可避免的光学损耗,分析了迈克耳孙干涉仪内部和外部的损耗对相位测量灵敏度的影响.通过理论计算研究了干涉仪的相位测量灵敏度随系统参数的变化关系,得到了高灵敏度的相位测量量子迈克耳孙干涉仪的实现条件,为用于精密测量的干涉仪的设计提供了直接参考.     

Shearograms of an optical phase singularity

Shearograms are known to represent phase gradients but when vortices are present in the optical field, these do not represent true phase gradients. Phase gradients of an optical phase singularity are presented. A lateral shear interferometer is used for obtaining shearograms of optical fields with vortices. A diffractive phase element is used to generate vortices. It is shown that shearograms can be used in the detection of optical vortices. Shearogram of speckle field is also presented.     

Fabrication of a void array in dielectric materials by femtosecond laser micro-processing for compact photonic devices

We describe a systematic investigation on void structures fabricated by femtosecond laser irradiation inside dielectric materials for fabrication of a compact optical circuit. Void shapes fabricated in 5 different dielectric materials were compared and the physical constants determining the void shape were discussed. A long void array is obtainable in a material which has a low critical power for self-focusing. It was also indicated that the coefficient of thermal expansion is a dominant governing factor to fabricate a precise void which has a clear boundary. Furthermore, we propose and design a Mach-Zehnder interferometer in fused silica composed of optical waveguides and photonic crystals to verify practical application of a void array. Simulation results of the optical propagation in a Mach-Zehnder interferometer indicated that the photonic crystals using a void array have potential to fabricate compact optical circuits.     

In situ measurement of group refractive index using tandem low-coherence interferometer

The group refractive index of BK-7 glass material is accurately measured using a tandem low-coherence interferometer, which is composed of a Mychelson interferometer and a Fizeau interferometer, within a combined standard uncertainty of 8.4 ppm. The experimental results are compared with the value calculated from the conventional data base on the phase refractive index, within a difference of about 4.7 ppm. This new method is applicable to in situ measurement due to the principle of its common optical path.     

空域移相偏振点衍射波前检测技术

点衍射干涉仪结构简单、共光路、测量精度高, 空域移相干涉仪抗振性能优越, 两者在波前检测领域获得了广泛的应用. 本文采用激光打孔技术, 通过在金属纳米线栅偏振片上制备小孔, 制作了偏振点衍射板; 结合分光结构的空域移相技术, 搭建了空域移相偏振点衍射干涉仪, 并对一焦距为550 mm, F_#10的平行光管准直物镜透射波前进行测量, 与法国Phasics公司生产的商业化波前传感器SID4的测量结果相比较, 两者峰谷值相差0.09λ, 均方根值相差0.012λ ; 利用35项Zernike多项式拟合两者的测量结果, 将拟合得到的系数在同一坐标轴下绘制成两条曲线, 两者基本重合, 从而验证了所搭建的空域移相偏振点衍射波前检测装置的测试精度. 从而在传统点衍射干涉仪的基础上引入了空域移相技术, 实现了波前的高分辨率、高精度、实时检测, 并且提高了对振动、气流等环境因素的抗干扰能力.     

An improved design of an integrated optical isolator based on non-reciprocalMach–Zehnder interferometry

Non-reciprocal rib waveguide structures can be used to realize integrated optical isolators. In this paper, we propose a concrete design for a Mach–Zehnder interferometer type isolator for TM modes. Just one of the arms, which are of equal length, is a non-reciprocal magneto-optic waveguide. The rest of the interferometer is reciprocal. Required fabrication tolerances are estimated, and the entire isolator is simulated by applying a finite difference beam propagation method.     

Phase synthesis of a holographic metrological diffraction grating of unlimited length

A breakthrough in the technology of measuring systems of submicrometre and subsecond precision was made possible by the invention of holographic phase aperture synthesis of highly regular interference structures. The practical fulfilment of holographic phase aperture synthesis requires development of the following new optical methods: (1) synthesis of the aperture by out of phase auxiliary holographic diffraction gratings; (2) high-precision analysis of the phase structure of the interference field; (3) automatic control of the aperture synthesis process using two-frequency modulation of the interference field; (4) an adaptive interferometer for aperture synthesis. This paper is devoted to the above methods.     

Mutual spatiotemporal coherence of optical fields in an amplitude-splitting interferometer

We have considered cross correlations of wave perturbations formed by optical fields at different points of space at the exit of an interferometer with the splitting of the amplitude of the initial wave field. Expressions for the longitudinal spatiotemporal cross-correlation function of perturbations on the optical axis of a Michelson interferometer have been obtained and analyzed. We have determined spatial and temporal intervals in which the wave fields excite mutually coherent perturbations in the exit channel of the interferometer in the free space and in the image space of the lens system. We have found that, in the free space, mutually correlated perturbations arise simultaneously in identical longitudinal intervals, whereas, in the image space, they arise at different times in spatial and temporal intervals varying along the optical axis of the lens. The influence of cross correlations of the wave fields on the interferometer signal has been analyzed.

     

Experimental determination of electric cross-spectral density matrix and generalized Stokes parameters for a laser beam

We report an experimental method to determine the elements of the electric cross-spectral density matrix for laser light. For this purpose an additional setup consisting of mirrors and reflecting prisms is utilized with the conventional Young's interferometer to overcome existing experimental limitations. The generalized Stokes parameters, which are the characteristics of two spatial points of the electromagnetic field, are also obtained for a pair of points. The knowledge of these two quantities might be useful in determining the change in polarization properties of light in propagation and their effects in optical measurements.     

Soliton squeezing in a highly transmissive nonlinear optical loop mirror

A perturbation approach is used to study the quantum noise of optical solitons in an asymmetric fiber Sagnac interferometer (a highly transmissive nonlinear optical loop mirror). Analytical expressions for the three second-order quadrature correlators are derived and used to predict the amount of detectable amplitude squeezing along with the optimum power-splitting ratio of the Sagnac interferometer. We find that it is the number-phase correlation owing to the Kerr nonlinearity that is primarily responsible for the observable noise reduction. The group-velocity dispersion affecting the field in the nonsoliton arm of the fiber interferometer is shown to limit the minimum achievable Fano factor.     

应用光学双稳原理的高精度光纤传感器

本文提出一种光纤干涉仪与光电混合光双稳装置相结合的新型光纤传感器.用光双稳开关脉冲计数度量温度变化,其测量精度比基于干涉条纹计数的一般干涉型光纤传感器的精度约高10～100倍,而且测量精度可调节.完成了这种传感器原理的模拟实验验证.     

Effect of decoherence of optical field with broad angular spectrum upon propagation through transparent media interfaces

The effects of the decoherence of a narrow-band optical field with a broad angular spectrum upon propagation through a plate of a transparent medium placed in one of the arms of the Michelson interferometer are established.