Quasi-optical analysis of a far-infrared spatio-spectral space interferometer concept

FISICA (Far-Infrared Space Interferometer Critical Assessment) was a three year study of a far-infrared spatio-spectral double-Fourier interferometer concept. One of the aims of the FISICA study was to set-out a baseline optical design for such a system, and to use a model of the system to simulate realistic telescope beams for use with an end-to-end instrument simulator. This paper describes a two-telescope (and hub) baseline optical design that fulfils the requirements of the FISICA science case, while minimising the optical mass of the system. A number of different modelling techniques were required for the analysis: fast approximate simulation tools such as ray tracing and Gaussian beam methods were employed for initial analysis, with GRASP physical optics used for higher accuracy in the final analysis. Results are shown for the predicted far-field patterns of the telescope primary mirrors under illumination by smooth walled rectangular feed horns. Far-field patterns for both on-axis and off-axis detectors are presented and discussed.     

Ground Layer Adaptive Optics

We will introduce the present knowledge of the turbulence profile and in particular we will emphasise the existence of a turbulence layer close to the ground. Then we will present the concept of Ground Layer Adaptive Optics and will provide estimates of performance expected from such systems and their potential for astronomical applications. Finally we will provide practical implementation concepts for two instruments at the VLT, MUSE and HAWK-I using multi-Laser Guide Stars and a large Deformable Secondary Mirror. The latter will also be described as its use is optimum for GLAO systems. To cite this article: N. Hubin et al., C. R. Physique 6 (2005).     

A label swapping technique using synchronous phase modulation without wavelength conversion

We demonstrate a label swapping technique for differential-phase-shifted-keying (DPSK) encoded labels using synchronous phase modulation (SPM). For the first time label erasure and insertion are performed in a single step without a need for wavelength conversion. The receiver sensitivity penalty of label swapping is limited to 1 dB when the timing mismatch between the new label and old label is kept from −18% to 18%.     

宽谱段折射式长焦光学镜头

介绍了宽谱段、折射式长焦镜头的光学设计.重点讨论了宽谱段(420～900 nm)二级光谱的校正问题,修正了部分色散（P）和阿贝数（V）的计算公式,使之适合于宽谱段光学系统的设计,并给出了设计实例及设计结果.本系统理论上的二级光谱约为1.2 mm,而设计结果使三条谱线（420 nm、600 nm、900 nm）基本交于一点,实际二级光谱约0.23 mm.     

Anisotropic laser trapping in nematic colloidal dispersion

The interaction between a colloidal particle and a focused laser beam in a nematic liquid crystal reveals an unusual anisotropic Coulomb-like character. Experiments demonstrate two opposite directions in which the particle is attracted to and repelled from the nematic region deformed by the light-induced director reorientation. In this work we present analytical analysis of such behavior and derive the energy of interaction between colloidal particle and deformed director field. The analytical solution is in good agreement with recent results obtained by computer simulation.     

基于集成光学的ICF脉冲整形系统

本文对基于集成光学的激光约束核聚变（ＩＣＦ）脉冲整形进行了系统研究,分析了这种新型脉冲整形技术与以往技术相比所具有的优越性能及所包含的关键技术成分,并指出了脉冲整形系统性能的影响因素     

Invited review

The studies of superlattices in ferroelectric crystals have made a rapid progress since 1980s. A superlattice is composed of modulated domains on the micron scale, controllable with modern techniques. It reveals a number of novel physical properties of optical and acoustic character. In this paper, we review recent advances in developing new techniques for fabrication and characterization of ferroelectric superlattices, and in exploring new physical effects for applications. The outlook for superlattice applications is briefly described.     

Characterization for stability in planar conductivities

We find a complete characterization for sets of uniformly strongly elliptic and isotropic conductivities with stable recovery in the $L^2$ norm when the data of the Calderón Inverse Conductivity Problem is obtained in the boundary of a disk and the conductivities are constant in a neighborhood of its boundary. To obtain this result, we present minimal a priori assumptions which turn out to be sufficient for sets of conductivities to have stable recovery in a bounded and rough domain. The condition is presented in terms of the integral moduli of continuity of the coefficients involved and their ellipticity bound as conjectured by Alessandrini in his 2007 paper, giving explicit quantitative control for every pair of conductivities.     

Stable Soliton Propagation in a System with Spectral Filtering and Nonlinear Gain

Stable soliton propagation in a system with linear and nonlinear gain and spectral filtering is investigated. Different types of exact analytical solutions of the cubic and the quintic complex Ginzburg-Landau equation (CGLE) are reviewed. The conditions to achieve stable soliton propagation are analyzed within the domain of validity of soliton perturbation theory. We derive an analytical expression defining the region in the parameter space where stable pulselike solutions exist, which agrees with the numerical results obtained by other authors. An analytical expression for the soliton amplitude corresponding to the quintic CGLE is also obtained. We show that the minimum value of this amplitude depends only on the ratio between the linear gain and the quintic gain saturating term.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.