Method of phase-dispersion introscopy

A method is described for studying the internal structure of noncrystalline objects which are weak x-ray absorbers. The method uses the conventional arrangement of plane-wave topography. The object to be investigated is immersed in a monochromatic pseudoplane wave formed by a highly asymmetric reflection off a perfect crystal or several crystals and introduces phase disruptions at the wave front. A perfect single crystal mounted behind the object in a Laue arrangement reveals these disturbances, forming a contrast image of the boundaries of the structural components of the object. The possibilities of the method are illustrated by photographs of objects of various natures. The features of the image contrasts are discussed and confirmed by experiments on test objects. Zh. Tekh. Fiz. 67, 68–77 (January 1997)     

Interferometric phase microscopy using slightly-off-axis reflective point diffraction interferometer

An interferometric phase microscopy (IPM) is proposed using slightly-off-axis reflective point diffraction interferometry for quantitative phase imaging. A retro-reflector consisting two mirrors is used to generate an angle between the object beam and reference beam, and a 45° tilted polarizing beam splitter is used to split the horizontal and vertical components of the both beams. Two carrier interferograms with π/2 phase-shift can be acquired in one shot, and the phase distribution of a thin specimen can be retrieved using a fast reconstruction method. The new IPM without loss in the utilization of the input-plane field of view combines the real time and optimizing detector bandwidth measurement benefit associated with slightly-off-axis method, high stability associated with common path geometry, and simplicity in terms of procedure and setup. Experiments are carried out on both static and dynamic specimens to demonstrate the validity and stability of the proposed method.     

Interferometric polarization coherent anti-Stokes Raman scattering (IP-CARS) microscopy

We report a novel interferometry-based polarization coherent anti-Stokes Raman scattering (IP-CARS) implementation for effectively suppressing the nonresonant background while significantly amplifying the resonant signal for vibrational imaging. By modulating the phase difference between the two interference CARS signals generated from the same sample and measuring the peak-to-peak intensity of the periodically modulated interference CARS signal, the IP-CARS technique yields a sixfold improvement in the signal-to-background ratio compared with conventional CARS while providing an approximately 20-fold amplification of the resonant CARS signal compared with conventional polarization CARS. We demonstrate this method by imaging 4.69 microm polystyrene beads and unstained human epithelial cells immersed in water.     

Birefringent interleaver with a ring cavity as a phase-dispersion element

We propose and demonstrate a novel ring-cavity-based flat-top birefringent interleaver. A single ring cavity provides the two phase shifts needed, each for a polarization state, to achieve a flat-top spectral passband at the output. Fresnel reflectivities (for s- and p-polarization states) at the prism interface of the ring cavity are employed so that highly accurate thin-film coatings are not needed for the phase shifts. By choosing the appropriate incident angle near the Brewster angle, we can obtain the optimum interface reflectivities for flat passbands and extremely low cross talk. We also present the results of our experimental investigations of a flat-top 25-GHz optical interleaver that uses a novel ring cavity architecture. In a 25-GHz channel spacing application the interleaver exhibits a 0.5-dB passband larger than 0.14 nm (17.5 GHz), a 25-dB stopband greater than 0.14 nm (17.5 GHz), and channel isolation better than 28 dB over the entire C band.     

Phase-Shifting-Free Interferometric Cryptosystem

Conventional phase-shifting interferometry-based(PSI-based)cryptosystem needs at least two-step phase-shifting.In this work,we propose a phase-shifting-free interferometric cryptosystem,which needs only one interferogram recording.Since the phase-shifting step is not required in the proposed cryptosystem,not only the low encryption speed which is a bottleneck problem of the conventional PSI-based one is solved,but also the setup of the cryptosystem is simplified.A series of simulation experimental results demonstrate the validity and robustness of the proposed cryptosystem.     

Interferometric array generation

We report the formation of square, rectangular as well as hexagonal arrays of small light spots in one single setup using Michelson and Mach–Zehnder interferometers in tandem. The geometry of arrays can be altered easily online, by changing the relative orientations of the mirrors. The arrays could be scanned over large longitudinal distances and could be compressed to give large spot density. The expression for the resultant intensity distribution for the arrays has been worked out and the computed pattern is compared with the experimental data.     

Interferometric spatial filtering

Spatial filters are realised interferometrically by the inclusion of a Mach-Zehnder interferometer in a spatial filtering system.     

Optical Interferometric MEMS Accelerometers

Laser interferometry is one of the most accurate measurement technologies whose displacement resolution can reach the femtometer (fm) level. With the development of Micro-Electro-Mechanical Systems(MEMS) technology, many excellent optical interferometric MEMS sensors have emerged, which play an essential role in intelligent manufacturing, aerospace, and many other fields. Among them, optical interferometric MEMS accelerometers develop rapidly due to their high sensitivity, low noise, and anti-electromagnetic interference advantages. Lots of research in optical interferometric chip design, micro-nano fabrication process, signal demodulation algorithm, and range extension technology are performed, and different types of MEMS accelerometers based on the optical interferometric principles are developed, which have been demonstrated and applied in the fields of disaster monitoring, equipment operation and maintenance, and resource exploration. This paper reviews the development status of optical interferometric MEMS accelerometers, mainly focusing on the critical problems and solutions that need to be solved in the development process of optical interferometric accelerometers, and finally introduces the typical application scenarios.     

Six-wave mixing phase-dispersion by optical heterodyne detection in dressed reverse N-type four-level system

We have investigated the dressed effects of non-degenerate four-wave mixing （NDFWM） and demonstrated a phase-sensitive method of studying the fifth-order nonlinear susceptibility due to atomic coherence in RN-type four-level system. In the presence of a strong coupling field, NDFWM spectrum exhibits Autler-Townes splitting, accompanied by either suppression or enhancement of the NDFWM signal, which is directly related to the competition between the absorption and dispersion contributions. The heterodyne-deteeted nonlinear absorption and dispersion of six-wave mixing signal in the RN-type system show that the hybrid radiation-matter detuning damping oscillation is in the THz range and can be controlled and modified through the eolour-locked correlation of twin noisy fields.[第一段]     

Interferometric Hetero-Detector Phase Measurement

We present a new method for the measurement of the phase of ultrashort optical pulses with high spectral resolution. This employs an interferometer with a monochromator in one arm. Two detectors operating in single photon and two-photon absorption regimes monitor the output from the interferometer. Comparison of the signals from the two detectors gives a measurement of the phase of the light pulse. The principles underpinning this technique are discussed and the experimental application to picosecond pulses is demonstrated.     

基于复合干涉的光纤低相干干涉传感系统研究

研究一种能够进行远程及绝对测量的光纤低相干干涉传感系统。该系统包含两个光纤干涉仪,其中一个光纤干涉仪置于被测场中感应被测量的变化,可实现远程测量;另一个光纤干涉仪解调被测量的值。运用波分复用技术,使用于解调的光纤干涉仪同时工作于低相干干涉和高相干干涉状态。用低相干干涉信号决定被测量的幅值,对被测量实现绝对测量,并使测量量程不受波长限制;同时,用高相干干涉信号对被测量进行高精度的测量。系统的测量量程为6mm,测量分辨率小于1nm,位移实验结果的线性相关系数R为0.99。     

Interferometric scanning of laser beams

A new beam deflection technique is based on modulating the optical transmission characteristics of a modified Fabry-Perot interferometer. Electro-optically changing the interferometer length leads to fast high resolution scanning of the transmission fringe. Experiments have been conducted using the 4880 Å argon laser line with an interferometer containing a LiNbO₃ crystal.     

Interferometric, modulation-free laser stabilization

We demonstrate novel modulation-free frequency locking of a diode laser, utilizing a simple Sagnac interferometer to create an error signal from saturated-absorption spectroscopy. The interference condition at the output of the Sagnac is strongly affected by the sharp dispersion feature near an atomic resonance. Slight misalignment of the interferometer and subsequent spatially selective, or tilt, detection allows this phase change to be converted into an error signal. Tilt locking has significant advantages over previously described methods, as it requires only a small number of low-cost optical components and a detector. In addition, the system has the potential to be constructed as a plug-and-play fiber-coupled monolithic device to provide submegahertz stability for lasers in the commercial market.     

Interferometric Computation Beyond Quantum Theory

There are quantum solutions for computational problems that make use of interference at some stage in the algorithm. These stages can be mapped into the physical setting of a single particle travelling through a many-armed interferometer. There has been recent foundational interest in theories beyond quantum theory. Here, we present a generalized formulation of computation in the context of a many-armed interferometer, and explore how theories can differ from quantum theory and still perform distributed calculations in this set-up. We shall see that quaternionic quantum theory proves a suitable candidate, whereas box-world does not. We also find that a classical hidden variable model first presented by Spekkens (Phys Rev A 75(3): 32100, 2007) can also be used for this type of computation due to the epistemic restriction placed on the hidden variable.     

Interferometric analysis for small rotation

Both holographic interferometry and speckle interferometry are used to analyse small rotation. The experimental set-up and results are presented. A brief comparison of the two methods is also given.     

Interferometric gratings with phase correction

A technique for producing diffractive optical elements uses holographic methods to incorporate into the recorded fringe pattern a correction factor for the phase defect of the substrate.     

Interferometric visualization of jet flames

This paper presents visualizations of reacting, round jets of the premixed and nonpremixed type realized by using interferometry and, complementarily, direct photography. The available interferometer, proposed by Carlomagno (1986), employs low-cost components and is flexible and robust to geometrical misalignments, allowing the drawbacks limiting the application of traditional interferometric systems to be overcome. Several flames are produced by varying the non-dimensional, governing parameters (Reynolds number, equivalence ratio, Grashof number). The results discussion is organized considering laminar, transitional and turbulent flows. In the steady, laminar case, in view of the radial symmetry of the fringes pattern, the temperature field is reconstructed by the interferograms. The structure of the transitional and turbulent combusting jets, primarily determined by shear layer destabilization mechanisms and large-scale vortices formation due to buoyancy, is analyzed and differences with isothermal flows are pointed out. In turbulent regime, studied only for premixed combustion case, qualitative insights into the structure of the reaction zone as a function of the equivalence ratio and turbulence properties in the incoming fresh mixture are also deduced.     

A Speckle Interferometric Flame Research Technique

Technical Physics - Methods of recording and automated processing of the results of phase-modulated speckle interferometry of optically dense (opaque to intrinsic radiation) flames containing a...