Heterodyne angular interferometer using a square prism

An interferometer composed of a dual-frequency laser, sensing assembly, and decoding system is proposed for angular displacement determinations. The laser is a heterodyne light source. The sensing assembly generates an interference signal by the use of a square prism, and the decoding system extracts the phase difference of the interference signal. The theory, which reveals that the phase difference has a relation with the angular displacement of the square prism, of the interferometer is described. A setup constructed to realize the interferometer and the results of using this setup are then demonstrated and presented.     

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.     

Broadband light source shearing interferometer using Savart plate and angular scanning technique

A shearing interferometer based on using broadband light source, Savart plate, and angular scanning technique is proposed for slope contour measurements in this Letter. Of which, the Savart plate divides the wavefront reflected from the detected surface into two laterally displaced ones, the interference pattern generated by the interference of the divided wavefronts is modulated by an envelope function, and the slope contour of the detected surface is determined by examining the shifting of the darkest fringe as the shear plate is angularly scanned. A setup for realizing the interferometer is constructed. The experimental results of using this setup agree the validity and feasibility of the proposed interferometer.     

Angular interferometer using calcite prism and rotating analyzer

An interferometer using a calcite prism and rotating analyzer is proposed for angular displacement determinations. The calcite prism senses the angular displacements and the rotating analyzer transfers the interference signals from dc-type into ac-type. Compact optical setup and using low-cost devices are thus the advantages of the interferometer. The theory of the interferometer is first demonstrated. A setup constructed to realize the interferometer and the results of using this setup are then presented.     

Shearing interferometer using low-coherent light source and calcite prism

A shearing interferometer using a low-coherent light source and calcite prism is proposed in this paper. The calcite prism is the shear plate that generates sheared wavefronts with optical-path difference induced only by the contour of the specimen. Low-coherent light source is thus available while the interferometer is adopted for contour derivative determinations. The design of this interferometer is introduced, a setup constructed to realize the interferometer is described, and the experimental results from the uses of the setup are finally presented.     

利用棱镜减小自衍射信号光角色散的研究

自衍射效应在飞秒激光领域有非常重要的应用,如提高飞秒脉冲的时域对比度、作为自参考光谱干涉脉冲测量法的参考光、作为频率分辨光学开关法的信号光等.然而,具有较宽光谱带宽的飞秒激光在自衍射效应过程中产生的信号光存在明显的角色散,这给自衍射效应的应用带来不利影响.本文研究发现通过在自衍射效应的一个光路中加入等腰直角棱镜,当到棱镜的入射角为23fi时可以明显地减小飞秒激光脉冲自衍射信号的角色散.这就为以后将自衍射效应更好的应用到飞秒激光脉冲的研究提供了有用的参考.     

Sub-50 nm patterning by immersion interference lithography using a Littrow prism as a Lloyd's interferometer

We present a simple setup that combines immersion lithography with a Lloyd's mirror interferometer. Aiming for smaller structure sizes, we have replaced the usual Lloyd's interferometer by a triangular Littrow prism with one metal-coated side, which acts as a mirror. Because of the higher refractive index of the prism, the wavelength and, thus, the attainable structure sizes, are decreased significantly. Using a laser with a wavelength of 244nm, we could produce line patterns with a period of less than 100nm and a width of 45nm. The introduced setup retains all the advantages of a Lloyd's mirror interferometer, in particular the flexibility in periodicity.     

Optics design of a top-cut prism interferometer for holographic photonic quasicrystals

Optical interference holography has been proved to be a useful technique in fabricating periodic photonic crystals in which electromagnetic waves are forbidden in certain frequency band-gaps. Compared to periodic crystals, quasicrystals have higher point group symmetry and are more favorable in achieving complete band-gaps. In this report, a top-cut prism interferometer is designed and optimized for photonic quasicrystals. By changing the prism parameters and characteristics of different beams, different quasicrystalline structures can be obtained. At the same time, the diffraction patterns of the designed structures are also provided and reveal the ten-fold symmetry of the structures more clearly. Furthermore, the effect of the intensity threshold on the quasicrystalline structures is also investigated. This will provide guidance for the large-area and fast production of ten-fold quasicrystalline structures with high quality.     

Visualization of flow past a square prism with cut-corners at the front-edge

Flow past a square prism with cut-corners at the front-edge is numerically and experimentally visualized to investigate a mechanism of drag reduction. An adaptive numerical scheme based on the vortex method is implemented for two values of the Reynolds number between 200 and 1,250, and the results are compared with experiments. Experimental visualization techniques include the hydrogen-bubble technique atRe=4,000 and the oil-flow technique atRe=10,000 for a global wake formation, and the aluminum-flake technique for transient flow at the early stage of motion atRe=1,250. A similar reattachment flow pattern is shown in a wide range of the Reynolds number between 200 and 10,000, which implies a possibility of the drag reduction in the Reynolds number being approximately lower than 8,000 unlike the previous findings.     

X-ray spectrum determination from the angular dispersion of radiation in a diamond prism

The X-ray spectrum of hard polychromatic radiation with energies of up to 40 keV was obtained from the angular dispersion of the radiation beam in a diamond prism. In contrast to the classical optical scheme, the beam to be analyzed is passed through the entrance face of the prism without refraction and is directed onto the exit face at a glancing angle ～(2δ)^1/2, where δ is the real part of the decrement of the refractive index for the short-wavelength edge of the spectrum. The spectrum distortions caused by the intersection of the reciprocal lattice points by the Ewald sphere at a fixed number of wavelengths λ are minimized by the use of the angular divergence of the beam of ～10′ in the plane perpendicular to the refraction plane. In the energy range of 8–9 keV, an energy resolution of less than 100 eV was obtained, which exceeds the corresponding parameter for cooled semiconductor detectors. The measuring scheme suggested makes it possible to solve the problem of the analysis of spectra of directional X-ray beams when studying fast nonstationary generation processes.     

Non-destructive collimation technique for measuring glass constants using a Ronchi grating shearing interferometer

A non-destructive liquid immersion collimation technique in combination with a Ronchi grating shearing interferometer has been used for determining the constants of a transparent glass material, especially when it is in the form of a lens. Due to its simplicity and the fact that it will work equally well at any wavelength, the technique is superior to existing methods for determining the various glass constants (refractive index, Abbe number or v-value, partial dispersion factor etc).The shearing fringes appearing inside a Ronchi-gram are adequate to locate the exact position of the point source which has been treated as the target in the present communication. The fringe-free space in the overlapping region between the two laterally displaced spherical wavefronts indicates the sharply focused position of the target which corresponds to zero defocusing. In this way the target displacements with different liquids are determined.     

Phase-difference amplification using a Sagnac interferometer

In this paper, we describe a new method for achieving phase-difference amplification, which is quick and convenient, operates in real time, and requires no photographic steps. Magnification factors of 2, 4 or 6 are achieved easily in one step. Because the system operates in real time, phase stepping may be applied to extract the amplified phase distributions. Our method is a variation on longitudinally reversed shearing interferometry, using first- or higher-order diffraction from a grating (hologram) which is in fact the interferogram of the wavefront under test. The grating is derived from a standard two-beam interferometer which is phase-stepped, and displayed in real time on a spatial light modulator in the phase-difference amplification setup. It is illuminated by the two output beams from a Sagnac interferometer, similar to the set up used by (Barnes et al. Barnes TH, Eiju T, Matsuda K. Appl Opt 1986; 25:1864). for spectral resolution enhancement, and a phase-amplified fringe pattern is obtained by spatial filtering using a Fourier transform lens. We demonstrate operation of the phase amplifier and show amplified phase maps retrieved by phase-stepping. We believe this is the first time that real-time phase amplification without photographic steps and with phase stepping has been demonstrated.     

Lensmeter using a lateral shearing interferometer

The use of a laser shear interferometer for checking the collimation condition within a lensmeter is proposed. The interferometer consist of a wedged glass plate which produces a shear along the orthogonal direction to the wedge; when the fringes at the center of the pattern are parallel to the shear, the collimation condition is attained. The feasibility of the proposal for measuring the vertex power is experimentally shown and the accuracy of the method is under 5% of the measured value being an improvement to the commercial instruments based on the focusing of a reticule.     

Implementing the Deutsch's algorithm with spin-orbital angular momentum of photon without interferometer

Deutsch's algorithm is the simplest quantum algorithm which shows the acceleration of quantum computer. In this paper, we theoretically advance a scheme to implement quantum Deutsch's algorithm in spin-orbital angular momentum space. Our scheme exploits a newly developed optical device called "q-plate", which can couple and manipulate the spin-orbital angular momentum simultaneously. This experimental setup is of high stability and efficiency theoretically for there is no interferometer in it.     

Subtraction of test mass angular noise in the LISA technology package interferometer

When the position of a test mass in one dimension is measured with picometer accuracy, angular alignment jitter inevitably couples noise into the measurement. We present recent sensitivity measurements of the LISA technology package interferometer with articulated mirrors as test masses, actuated by piezo-electric transducers. The required longitudinal displacement resolution of 9 pm above 3 mHz has been demonstrated with an angular noise that corresponds to the expected for on-orbit operation. The excess noise contribution of this test mass jitter onto the sensitive displacement readout was completely subtracted by fitting the angular interferometric data streams to the longitudinal displacement measurement. Thus, this cross-coupling constitutes no limitation to the required performance of the LISA technology package interferometry. PACS 04.80.Nn; 07.60.Ly; 42.62.Eh     

Speckle shearing interferometer using a Savart plate

We describe a speckle shearing interferometer using a Savart polariscope. The purpose of this interferometer is to obtain the derivative of the out-of-plane displacement suffered by a scattering surface when put under stress. This information is useful to know the bending moments. The setup is compact, very stable, and does not require any stringent adjustment.     

Three-dimensional coordinate measurements using a multiple-pinhole interferometer

We propose a method for noncontact measurements of three-dimensional (3D) coordinates based on a Y-typed multiple-pinhole (MP) interferometer and demonstrate its feasibility in experiments. In this method, a Y-typed MP plate is inserted between the target and an image sensor to form a common-path interferometer. The 3D coordinates of the target are found by an effective algorithm using the discrete phase values on the measurement pinholes of the MP plate. These phase values can be directly extracted from a Fourier transform of the recorded intensity pattern without need of any iterative or phase-shifting algorithm. The method could be significant in real-time coordinate measurements and position tracking applications.     

Differential thickness measurement using a polarization interferometer

A method for measuring the differential thickness of a thin film using a polarization interferometer is described. Theoretical estimation shows that the measurement error is less than 0.1%. Experiments performed on a PZT sample indicate high sensitivity and excellent linearity of the system. PZT expansions ranging from 300 nm to less than 1 nm could be measured with a precision better than 0.1 nm.     

利用全光纤干涉解调技术的光纤光栅复用传感系统

提出了一种用于光纤光栅传感波长检测的新方法。系统采用全光纤Mach Zehnder干涉仪,运用动态的自参考相位检测方式,结合微机实时处理技术,实现了对三点复用传感器的高分辨率(0.99pm)解调,单点测量范围达3.32nm。系统结构简单、成本低,可以同时检测静态和低频动态信号。     

Multipass interferometer using a filamentary spatial filter

A multiple pass interferometer using a filamentary spatial filter is developed. We can change the sensitivity of the interference fringe pattern by selecting the order of multiply reflected image without reduction of the fringe visibility.