Quantum-optical Phase and Canonical Conjugation

Abstract

We use a new limiting procedure, developed to study quantum-optical phase, to examine canonically conjugate operators in general. We find that Dirac's assumption that photon number and phase should be canonically conjugate variables, similar to momentum and position, is essentially correct. The difficulties with Dirac's approach are shown to arise through use of a form of the canonical commutator which, although the only possible form in the usual infinite Hilbert space approach, is not sufficiently general to be used as a model for a number-phase commutator. The approach in this paper unifies the theory of conjugate operators, which include photon number and phase, angular momentum and angle, and momentum and position as particular cases. The usual position-momentum commutator is regained from a more generally applicable expression by means of a domain restriction which cannot be used for the phase-number commutator.     

Picosecond Phase Conjugation in Sodium Vapour

Abstract

Phase conjugation by degenerate four-wave mixing in sodium vapour was demonstrated using 80 ps transform-limited pulses. Values of the phase-conjugated reflectivity were measured as a function of the temperature of the vapour and the delay of the probe beam.     

Atomic Phase Conjugation From a Bose Condensate

We discuss the possibility of observing atomic phase conjugation from Bose condensates, and using it as a diagnostic tool to access the spatial coherence properties and to measure the lifetime of the condensate. We argue that since phase conjugation results from the scattering of a partial matter wave off the spatial grating produced by two other waves, it offers a natural way to directly measure such properties, and as such provides an attractive alternative to the optical methods proposed in the past.     

被动相位共轭处理在水声通信中的应用

由于海洋信道的复杂性,要实现可靠的水下声通信,必须进行有效的信道匹配.本文描述了一种能利用信道特性的信道匹配技术-被动相位共轭处理.仿真计算结果表明该技术在水下声通信中有很好的应用前景.     

Phase Conjugation in Degenerate Four-wave Mixing with Finite Apertures

The phase-conjugate field fidelity in backward-going four-wave mixing, based on the diffraction model solvable analytically, is investigated. The method assumes interaction of the non-depleted infinite plane pump waves with the spatially limited probe and signal waves inside the nonlinear medium. Solutions are obtained applying the Fourier transformation and the Green function technique under various boundary conditions for coupled wave equations. The probe and its phase-conjugate waves are defined by using a complex phase formulation including both the phase variation and amplitude modulation. It is shown that the analysed approach can involve assumptions leading to the ideal or distorted phase conjugation.     

Picosecond Phase Conjugation and Two-wave Coupling in Strontium Barium Niobate

Abstract

Picosecond phase conjugation and two-wave coupling in cerium-doped strontium barium niobate at 778 nm were studied. The phase conjugation reflectivity at 778 nm was measured to be R _pc = 58%. It is close to that pumped by a continuous-wave pump source. The temporal width t _pc and spectral width δγ_pc of the phase conjugate pulse were measured to be the same as that of the pump pulse. The intensity coupling gain of two-wave coupling as a function of time delay τ_D between two beams was also studied.     

Phase Conjugation by Degenerate Four-wave Mixing in Inverted Dye Solutions

Abstract

Phase conjugation has been observed in an amplifying medium of rhodamine 6G dye molecules in solution, excited either by flashlamps or by a laser. It is found that the mechanism involved in phase conjugation is degenerate four-wave mixing through gain saturation, and reasonable agreement obtained with the theory of saturable amplifiers. A phase-conjugate signal was observed over the tuning range of the dye system (580–605 nm) and a reflectivity up to a maximum of 25% was obtained.     

引入声汇的相位共轭方法进行声场识别

在时间反转方法中引入声汇概念的基础上,提出两种方法计算引入的声汇幅值：第一种方法是直接推导出相位共轭阵列在声源聚焦处的幅值,将其作为声汇的幅值;第二种方法是在近场引入一个测量球面计算声汇的幅值,并讨论引入测量球面半径对声场重建结果的影响。数值计算结果表明：引入声汇之后,在一定的测量距离上,采用两种计算方法都能突破声波的衍射极限;通过引入的测量球面方法,采用封闭的球形阵列在远场也能突破声波的衍射极限,得到结果更精确,与点声源理论解吻合较好;根据倏逝波传播性质,引入的测量球面半径需小于一个波长。     

High-intensity Effects in Self-pumped Photorefractive Phase Conjugation Using Nanosecond Pulses

Abstract

This paper reports on self-pumped photorefractive phase conjugation using repetitively pulsed high intensity (MW cm^?2) pulses of nanosecond duration. An intensity-dependent phase conjugate reflectivity is measured experimentally. In the corner self-pumped geometry the direction of beam fanning and corner self-pumping is observed to reverse above a critical intensity. Formation of a higher order spatial mode is reported for the external loop self-pumped geometry.     

Multipass Amplification Using Optical Phase Conjugation by Stimulated Brillouin Scattering

Abstract

We built up a multipass amplifier for multiplication of infrared nanosecond pulses based on stimulated Brillouin scattering in acetone. Starting with a Q-switched Nd-doped yttrium aluminium garnet oscillator emitting pulses with less than 5 ns duration, we were able to generate a train of up to five pulses with a pulse shortening. Because only phase-conjugating mirrors have been used, we expect the pulses to have a high transverse homogeneity.     

Phase Conjugation of a Plane Electromagnetic Wave at an Interface

Boundary conditions for electromagnetic waves which undergo phase conjugation at an interface between two media of different refractive index are considered. Appropriate laws of reflection and refraction are derived, showing a certain symmetry with ordinary interaction at a boundary, and affecting the Fresnel equations accordingly.     

用相位共轭法进行平板辐射声场的识别

基于相位共轭方法采用数值方法对平板辐射声场进行识别和重构,采用不同的阵列形式重构了平板的法向速度,辐射声功率以及声强。数值计算结果表明：在近场基于声压梯度测量使用偶极子源的平面相位共轭阵列形式对声场重构的效果最好,并能准确识别平板的法向速度,辐射声功率以及声强。相位共轭方法具有测点少,可自然使用局部重建方法,不存在解不稳定问题等优点,具有很好的应用前景。     

Polarization Characteristics of Phase Conjugation at Four-wave Mixing in Uniaxial Crystals

The phenomenon is considered of degenerate phase conjugation at four-wave mixing in uniaxial crystals. Polarization characteristics are calculated. The cases of complete and incomplete phase conjugation are analysed.     

On the Scattering Matrix of Multimode Fibres for Polarization Recovery by Phase Conjugation

Abstract

A phenomenological model for the scattering matrix of a long mode-scrambling optical fibre is derived, predicting incomplete polarization information recovery using a single-polarization phase-conjugating mirror at the fibre output, in agreement with some recent experimental findings.     

配制配合中实际尺寸测量误差对配合公差的影响

阐述了在配制配合中由于先加工件实际尺寸与测量误差的来源及其所引起的配合公差的变化以及它对配合件配合性质的影响, 给出了配制配合公差的计算方法和在单件小批生产时配合公差超出给定值的可能性。最后还给出了为保证配制配合设计和实际尺寸检测时应采取的措施。     

高斯光束强度共轭的数值模拟

本文从傍轴波动方程出发,在线性化假设下,导出了任意振幅分布的发射场相位与接收场振幅分布之间的解析关系式,并对高斯光束进行了数值模拟。模拟结果表明,衍射场强度与要求场强度之间符合较好。最后对数值模拟结果进行了讨论。