Formation of quasi-regular diffraction patterns in the nonlinear photorefractive Fabry-Perot interferometer

Formation of optical inhomogeneities under self-action of light fields in photorefractive Fabry-Perot interferometers has been experimentally investigated using the samples of Y — and Z-cut lithium niobate. For the interferometer with the Z-cut sample, it is demonstrated that spiral-shaped inhomogeneities and two-dimensional quasi-regular diffraction patterns are formed under the effect of the Gaussian beam about 1mm in diameter and the light field with a homogeneous intensity distribution.     

Enhanced four-wave mixing in a high-finesse highly nonlinear fiber Fabry-Perot resonator

We have achieved a four-wave mixing process in a high-finesse highly nonlinear fiber Fabry-Perot resonator, where the amplified signal and idler were enhanced in transmission by 6 dB and 10 dB respectively comparing with those in a single fiber. We used a 6 m long low-loss Fabry-Perot resonator with two high-reflectivity fiber Bragg gratings written directly into a highly nonlinear fiber provided by Sumitomo Electric Inc., where the minimised intracavity loss resulted in the finesse in excess of 100. The resonator length was locked for 30 min by means of a modified Pound-Drever-Hall technique. The maximum intracavity power was increased by 14.3 dB by increasing the stimulated Brillouin scattering threshold with periodic phase modulation by a pseudo-random bit sequence, with length matching that of the cavity.     

Hysteresis and nonlinear thermooptic waves in a semiconductor Fabry-Perot interferometer

We propose and demonstrate the existence of temperature hysteresis phenomena in a Fabry-Perot interferometer, resulting from a change in the refractive index of the interferometer material when heated by laser radiation. We also demonstrated theoretically that temperature multistability in the distributed interferometric system may cause the emergence of nonlinear thermooptic switching waves and found an approximate expression for the propagation velocity of such waves. We present the results of experimental observations of temperature multistability and thermooptic switching waves in a germanium Fabry-Perot interferometer illuminated by CO₂-laser radiation.     

Transformation of the amplitude profiles of coherent light beams in a nonlinear photorefractive Fabry-Perot interferometer

The transformations of the transverse profiles of laser beams in a nonlinear Fabry-Perot interferometer based on lithium niobate crystals with a surface layer doped with a combination of photorefractive impurities (iron and copper ions) have been experimentally investigated. It is demonstrated that the distribution of transmitted beam intensity significantly changes for a few seconds at milliwatt beam powers.     

Limiting instrumental function of the Fabry-Perot interferometer

Journal of Applied Spectroscopy -     

Theory of the Fabry-Perot interferometer with nonparallel reflectors

Taking into account the wave structure of the light beam, determined by diffraction theory, we consider the harmful effect of the inclination of the mirrors of a Fabry-Perot interferometer when fringes of equal inclination are being observed. It is found that the contrast and resolution of the fringes of equal inclination are reduced as the angle of the wedge so formed is increased, and the interferometer (resonator) completely loses its high-resolution capability (Q-factor) when the mirrors deviate from parallelism by an angle equal to half the diffraction angle at its aperture. The advantages of stopping down both the incoming and outgoing beams in improving the contrast and increasing the resolution of the fringes of equal inclination are pointed out.The author thanks Professor F. A. Korolev for his interest.     

扫描式法布里-珀罗干涉仪测量高空大气风速

为测量中低纬度地区250km高空大气风速，采用扫描式法布里 珀罗干涉仪记录250km高度附近的OI630nm气辉辐射谱线的干涉图像。通过对观测图像分析处理，用高斯函数匹配干涉条纹强度分布以确定干涉条纹强度中心的精确位置，进而求出谱线的多普勒频移，反演出经向和纬向风速。经过理论推导，求出F P腔间距的漂移量对风速的影响，对反演风速进行修正。由风速随时间变化曲线得到在观测期间，经向风朝南，大小在4～67m/s间变化；纬向风朝东，大小在20～100m/s间变化，最小风速误差约为6m/s。     

Dynamics of the nonlinear four-wave mixing interaction

We present an analysis of the impulse response of four-wave mixing, in the case where the two-photon term of the nonlinear susceptibility is dominant. The nonlinear interaction itself will be considered to be steady state. The conditions of negligible pump depletion are considered first. It is shown that the reflected beam has only the character of perfect phase conjugation if the pulse length is longer than the medium length, and the latter is short compared to the characteristic distance of the problem. The weak-pulse approximation involving only two coupled equations is compared to the exact four-wave solution, when the medium thickness approaches the critical oscillation threshold. Finally, the stability and existence of steady-state solutions is analyzed for very long media (compared with the oscillation length).     

On the finesse of a phase-conjugate Fabry-Perot resonator using nearly-degenerate four-wave mixing

We consider a Fabry-Perot cavity in which one of the mirrors is a phase-conjugate mirror (PCM) using near-degenerate four-wave mixing. We show that when taking pump depletion into account, the divergence in finesse of the resonator predicted by linear theories for a resonator round trip gain approaching unity is eliminated. The saturation of the finesse as a function of pump intensity leads to a new kind of bistability in the transmission characteristics of the system.     

非共振条件下高斯光束斜入射法布里-珀罗干涉仪的透射特性

基于多光束干涉原理,研究了当高斯光束的载波频率与法布里—珀罗(F P)干涉仪的谐振频率存在偏差(即非共振)时,高斯光束斜入射F P干涉仪的透射特性。结果表明,与共振情况相比,非共振条件下透射光束的峰值强度及其所对应的位置、以及光斑的大小随入射角的变化都发生了显著的改变。     

Downstream Fabry-Perot interferometer for acoustic wave monitoring in photoacoustic tomography

An optical detection setup consisting of a focused laser beam fed into a downstream Fabry-Perot interferometer (FPI) for demodulation of acoustically generated optical phase variations is investigated for its applicability in photoacoustic tomography. The device measures the time derivative of acoustic signals integrated along the beam. Compared to a setup where the detection beam is part of a Mach-Zehnder interferometer, the signal-to-noise ratio of the FPI is lower, but the image quality of the two devices is similar. Using the FPI in a photoacoustic tomograph allows scanning the probe beam around the imaging object without moving the latter.     

Quantum effects of a nonlinear interferometer with a Kerr cell

With the help of the optical Kerr effect we can produce phase fluctuations caused by intensity fluctuations. For this effect we present an exact solution in the Heisenberg picture. Interference of such a light beam with a reference beam produce enhanced bunching as well as antibunching of weak fields.     

Submicrometer fiber-optic Fabry-Perot interferometer formed by use of the Langmuir-Blodgett technique

The fabrication of an optical cavity at the distal end of an optical fiber has been achieved by Langmuir-Blodgett (LB) deposition of tricosanoic acid. This technique allows nanometer-scale control over the cavity length to a total thickness of ~0.5 microm . The cavity has been shown to act interferometrically and, thus, has potential sensing applications.     

The use of the Fabry-Perot interferometer for high resolution microwave spectroscopy

A simple Fabry-Perot interferometer was used for measurements of microwave spectra. Both basic experimental arrangements, absorption and emission, were tested on the rotational spectra of acetonitrile. The interferometric results obtained were compared with the spectra measured using a standard high resolution microwave spectrometer.     

Structuring mechanism in a nonlinear fizeau interferometer: Two-dimensional effects and the bifurcation pattern

Forming is examined for a nonlinear Fizeau interferometer with two-dimensional feedback [1]. A previous paper [2] dealt with explaining the formation mechanism for simple optical structures and detailed interferometer an input beam parameters. Here we consider factors responsible for the rate of change in the phase shift u(x, y, t) in a beam cross section; the role of the nonlinearity is considered in detail, which determines the number of possible states of u(x, y, t), and the limits to the applicability of the approach are considered. Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 10–14, March, 1997.     

Focusing effects in nonlinear resonant four-wave mixing (RFWM) MIR and FIR generation

Summary The influence of pump beam geometry in a NH₃ superradiant Raman FIR laser with RFWM generation of MIR emission has been analysed. We have observed that, in general, MIR radiation is emitted in a stimulated configuration, so pump and MIR beam overlap is basically important to exhibit an efficient RFWM. In particular, strong focusing, also in the presence of self-focusing, shows a lowering of the threshold of Raman FIR emission, as expected, plus a reduction of RFWM MIR emission. COMB-Arrich., CRE Frascati.