Switchable vector vortex beam generation using an optical fiber

We present our experimental results on directly transforming a circular-polarized Gaussian beam into linear-polarized vector vortex beams using a two-mode fiber and demonstrate switching between the different 0th-order vector vortex modes excited and guided in the fiber. Depending on the handiness of circular-polarization of the input Gaussian light beam, its launch angle with respect to the fiber axis and by changing them appropriately it is possible to excite and switch between the different vector vortex modes and its coherent linear superposition supported by the two-mode fiber. The output optical beams due to the selectively excited vector modes in the fiber are characterized by using a rotating analyzer and a two-beam interferometer setup to study the polarization and the phase behavior of the vector vortex beam.     

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.     

Realization of an optical interferometer based on holographic optics for real-time testing of phase objects

The paper describes a simple and cost effective method for the realization of an optical interferometer based on holographic optics, which use minimal bulk optical components. The optical arrangement in the proposed method involves a very simple alignment procedure and inexpensive holographic recording material is used in the formation of holographic optical elements. The proposed interferometer set-up is quite suitable for performing optical test studies on phase (transparent) objects in real-time. Recording schemes for the formation of holographic optical elements and the related technique for the realization of the interferometer set-up along with the experimental results have been presented.     

Mach–Zehnder interferometer with squeezed and EPR entangled optical fields

We study a scheme for Mach-Zehnder(MZ) interferometer as a quantum linear device by injecting two-mode squeezed input states into two ports of interferometer.Two-mode squeezed states can be changed into two types of inputs for MZ interferometer:two squeezed states and Einstein-Podolsky-Rosen(EPR) entangled states.The interference patterns of the MZ interferometer vary periodically as the relative phase of the two arms of the interferometer is scanned,and are measured by the balanced homodyne detection system.Our experiments show that there are different interference patterns and periodicity of the output quantum states for two cases which depend on the relative phase of input optical fields.Since MZ interferometer can be used to realize some quantum operations,this work will have the important applications in quantum information and metrology.     

System for measuring optical admittance of a thin film stack

A new method based on the polarization interferometer structure has been applied to measure the optical admittance, the refractive index and thickness of a thin film. The structure is a vibration insensitive optical system. There is one Twyman-Green interferometer part to induce a phase difference and one Fizeau interferometer part to induce the interference in the system. The intensities coming from four different polarizers were measured at the same time to prevent mechanical vibration influence. Using the polarization interferometer, the optical admittance, the refractive index and thickness of a single layer of Ta₂O₅ thin film has been measured. The measurement results were compared with the results obtained by ellipsometer. The results meet reasonable values in both refractive index and thickness.     

Spatial-Variant Geometric Phase of Hybrid-Polarized Vector Optical Fields

We investigate a novel spatial geometric phase of hybrid-polarized vector fields consisting of linear, elliptical and circular polarizations by Young's two-slit interferometer instead of the widely used Mach-Zehnder interferometer.This spatial geometric phase can be manipulated by engineering the spatial configuration of hybrid polarizations,and is directly related to the topological charge, the local states of polarization and the rotational symmetry of hybrid-polarized vector optical fields. The unique feature of geometric phase has implications in quantum information science as well as other physical systems such as electron vortex beams.     

使用子孔径拼接法检测大口径光学元件

为了解决大口径光学元件检测过程中成本高、空间分辨率低这两个主要难点 ,提出了使用小口径、高精度干涉仪分次检测大口径元件 ,然后通过优化算法将检测结果进行拼接处理 ,最终得到原大口径元件波前信息的方法 ,并作了初步的拼接模拟实验 ,确认了这一方案的可行性。     

光学纳米测量方法及发展趋势

综述了光学方法中以频率跟踪方法、外差干涉仪、调频干涉仪、偏振干涉仪和光学光栅为代表的光学纳米测量方法。分析了它们的发展状况以及各自特点,指出建立适合于纳米测量的纳米环境是目前亟待解决的关键性问题,给出了光学纳米测量方法的发展方向和在设计测量系统时应该注意的问题     

Measurement of small chirp-parameter for Mach-Zehnder-type optical modulator

A new measurement method of chirp-parameters is proposed for electro-optic (EO) intensity modulators with the Mach-Zehnder (MZ) waveguide interferometer. This method is suitably applied for the measurement of the small chirp with operation at a specific RF-frequency. To determine the chirp-parameter, optical spectrum components of the modulated light are observed with varying the relative optical phase difference between the two arms of the MZ waveguide interferometer. The chirp-parameter of 0.17, which is a value small enough for EO intensity modulation, was successfully measured by the experiment.     

Step-profile measurement by backpropagation of multiple-wavelength optical fields

Multiple-wavelength optical fields on a detecting plane of an interferometer are generated from the interference signals detected for an object surface. The generated optical fields are backpropagated along the optical axis. An optical field along the optical axis is reconstructed by summing the backpropagated fields over the multiple wavelengths. The intensity and phase distributions of the reconstructed optical field provide the position of the object surface with an accuracy of a few nanometers.     

Electronic speckle-pattern interferometer using holographic optical elements for vibration measurements

We report a simple, compact electronic speckle-pattern interferometer (ESPI) incorporating holographic optical elements (HOEs) for the study of out-of-plane vibration. Reflection and transmission HOEs provide reference and object beams in the interferometer. The alignment difficulties with conventional ESPI systems are minimized using HOEs. The time-average ESPI subtraction method is used to generate the fringe pattern and remove background speckle noise by introducing a phase shift between consecutive images. The amplitude and phase maps are obtained using path-difference modulation.     

高灵敏度光纤弱磁传感器

本文报道了一种磁场检测灵敏度为10~(-5)Oe量级的光纤弱磁传感器。文中提供了传感头与检测系统的设计理论和方法。     

Polarization phase-shifting interferometer by rotating azo-polymer film with photo-induced optical anisotropy

A new type of phase-shifting interferometer was presented by rotating an azo-polymer film with photo-induced optical anisotropy in the light path of orthogonal polarization interferometry. By changing the angle of the optical axis of the azo-polymer film, four phase-shifted fringe patterns were obtained, from which phase difference between orthogonal polarized light could be calculated. The polarization states and the formation of the interferograms were analyzed theoretically using Jones matrix calculations and the experimental verification of the proposed method was also given. This method has a simple optical configuration which utilizes commercially available polarization devices and anisotropic azo-polymer film of low cost. The phase-shifting interferometer also demonstrates a new application of azo-polymer film.     

All optical logic NAND gate based on two-photon absorption in semiconductor optical amplifiers

We propose a new scheme to realize all optical logic NAND operating at high speeds up to 250 Gb/s utilizing the ultrafast phase response during two-photon absorption (TPA) process in semiconductor optical amplifiers (SOA). NAND gate is important because other Boolean logic elements and circuits can be realized using NAND gates as basic building blocks. Rate equations for semiconductor optical amplifiers (for input data signals with high intensity) configured in the form of a Mach-Zehnder interferometer have been solved. The input intensities are high enough so that the two-photon induced phase change is larger than the regular gain induced phase change. The performance of this scheme is analyzed by calculating the quality factor of the resulting data streams. The results show that both AND and NAND operations at 250 Gb/s with good signal to noise ratio are feasible.     

Laser optical fibre heterodyne interferometer with frequency indicating of the phase shift of a light signal in an optical waveguide

Self-sustained oscillations in a laser optical fibre heterodyne interferometer are discussed; oscillations were produced by closing into a loop the single-mode optical fibres of the interferometer. Such oscillatory systems are shown to feature high-frequency stability. It is proposed to use this oscillating interferometer as a high-sensitivity sensor of external factors affecting the optical waveguide.     

Interferometry with optical pickups

We describe an interferometer that makes use of an optical pickup. This widespread consumer electronics component has a high degree of technological content. A typical head contains a remarkable, highly integrated sample of optoelectronic laboratory equipment. The application that we report is a significant and novel example of the potential exploitation of the unique features of such a device for scientific aims. Many interferometric configurations can be envisaged, depending on the specific pickup design. We present a Fizeau multiphase homodyne interferometer that makes use of an astigmatic-focus-detection pickup. Its quadrant detector provides four photocurrent signals whose phase delays can be easily controlled. This allows us to apply phase-shifting interferometry algorithms for data reduction.     

风场探测干涉仪中基准光程差的选择原理

为了确定风场成像干涉仪（Wind Imaging Interferometer,WINDII）中存在的基准光程差的值,首先从风场探测机理出发,分析了影响基准光程差的因素.针对WINDII分别从调制度、相位及相近谱线同相的要求三个方面加以剖析,依次获得了它们与基准光程差之间的定量关系.综合考虑三个条件的要求,最终得出了基准光程差的选择原理.并用此理论对几种不同的风场成像干涉仪的基准光程差值进行了验证.     

基于单元件干涉仪的计算机断层扫描重建光纤三维折射率分布

提出了一种基于单元件干涉仪的计算机断层扫描方案,用于测量光纤三维折射率分布。该单元件干涉仪基于显微成像的原理,提高了系统的横向分辨率。利用快速傅里叶变换提取相位,采用滤波反投影算法重建了光纤的折射率分布。搭建了实验测量装置,实际测量了单模和多模光纤的折射率分布。结果表明,提供的方法可以简单快速地得到全光场数据,同时具有无损和非接触的优点,并且光路结构紧凑稳定,可为计算机断层扫描设备的小型化提供一种新的思路。     

Self-referenced Doppler optical coherence tomography

Doppler optical coherence tomography (DOCT) allows simultaneous micrometer-scale resolution cross-sectional imaging of tissue structure and blood flow. We demonstrate a fiber-optic polarization-diversity-based differential phase contrast DOCT system as a method to perform self-referenced velocimetry in highly scattering media. Using this strategy, we reduced common-mode interferometer noise to <1 Hz and improved Doppler estimates in a scattering flow phantom by a factor of 5.     

Highly sensitive interferometric system for optical surface contouring

In the present work we demonstrate a highly sensitive system for optical surface contouring constructed by combining phase conjugation and digital phase shifting interferometry. The phase conjugating mirror in the modified phase conjugate Michelson interferometer is based on degenerate four wave mixing in a photorefractive BTO crystal. Digital phase shifting interferometry is used to decode the interference fringe pattern. An increase in sensitivity and high measurement accuracy are achieved through this new combination due to the interferometric scheme and the phase shifting. Experimental results are presented. The interferometric system is flexible and undergoes further improvement.