A far infrared scanning plane Fabry-Perot spectro interferometer

We describe a mounting fitted to select a narrow frequency band between 20 and 100 cm^?1 in the far infrared; it consists of a coupling of a grating monochromator with a plane scanning Fabry-Perot interferometer (F. P.). This apparatus is intended for the fine study of profiles, pure rotation line broadening and shifting of simple dipolar molecules perturbed under low pressure.     

A vibrationally compensated far infrared laser interferometer for plasma density measurements

A modulated far-infrared laser interferometer which is presently operating on the PDX experiment at Princeton is described. The interferometer geometry permits the characterization of inside “D”, outside “D” as well as circular discharges. To achieve this versatility, a titanium corner cube reflector, mounted inside the PDX vacuum vessel is used in conjunction with a second visible wavelength interferometer for vibration corrections. In addition, the use of room temperature quasi-optical Schottky diodes in the far-infrared interferometer is reported. The minimum detectable line average density of the system is ～5×10¹¹ cm^?3.     

A two-beam interferometer for dispersive reflection spectroscopy of solids in the far infrared at temperatures between 4 and 300K

A Fourier spectrometer has been developed for determining the optical constants of highly absorbing solids in the far infrared at temperatures down to 4.2K from measurements of their amplitude and phase reflection spectra. The spectrometer has been constructed almost entirely from commercially available components, and its performance is illustrated with measurements of the optical constants of NaCl at 6K.     

A tunable far infrared laser

A continuously tunable far infrared (FIR) laser has been demonstrated; experimental results are presented. A high-pressure (10-12 atm) continuously tunable CO2TE laser is used to pump Raman transitions in CH3F; the generation of continuously tunable radiation in the250-300 mum wavelength range is reported. Accurate frequency and bandwidth measurements have been made and the FIR bandwidth in superradiant emission isapprox4-5GHz. Consequently, the generation of frequency tunable, subnanosecond pulses in the FIR appears feasible. The generation of tunable laser radiation from 150 to 1000 μm by stimulated Raman scattering should be possible using higher pump intensity and/or other gases.     

一种新型远红外声光调制器

介绍一种新型远红外声光调制器,采用高品质因子Ge单晶(III)方向传声作为声光介质,铌酸锂晶体作为压电换能器,工作中心频率为80MHz;还介绍了两种散热结构,经测试比较,环绕散热结构比背面散热结构的衍射效率提高10%,而且光斑质量也明显变好,较大地提高了远红外声光调制器的性能,利用10W高频驱动功率,测得锗声光器件的峰值衍射效率为65%。它的成功为声光调制器在激光雷达、远距离目标跟踪等方面的远红外技术应用,具有实际意义。     

A design procedure for classical offset dual reflector antennaswith circular apertures

A geometrical optics procedure for designing electrically optimized classical offset dual reflector antennas with circular apertures is presented. Equations are derived that allow the size and spacing of the main and subreflectors of the antenna system, along with the feed horn subintended angle, to be used as input variables of the design procedure. The procedure, together with these equations, yields an optimized design, starting from general system requirements. The procedure is demonstrated by designing both an offset Cassegrain and an offset Gregorian antenna, and is validated by analyzing their radiation patterns using physical optics surface current integration on both the main and subreflectors     

Realisation of generalised far fields by reflector synthesis

A method of designing reflector surfaces by the geometrical-optics approximation is introduced, in which a given generalised far field is realised when the reflector is illuminated by a point source. The problem is shown to be reduced to solving a nonlinear 2nd-order partial differential equation of the Monge-Ampère type. A computed example is given.     

A variable reflectivity output coupler for optically pumped far infrared lasers

In this paper we describe the design and performance of a variable reflectivity output coupler for optically pumped far infrared (FIR) lasers. The output coupler is a compact, tunable Michelson interferometer. The output coupling ratio (i.e. the Michelson transmission) is adjustable between 0 and ≥60% for laser line wavelengths between 110 and 500 μm. This output coupler provides increased output power and flexibility, since it can be tuned to optimum coupling ratio for different laser lines. Beam profile measurements show that the Michelson output coupler produces a well collimated Gaussian laser beam. Design features are a) the use of 10 μm reflection coated quartz vacuum window which acts as a dichroic mirror for the pump radiation and b) the high mechanical stability obtained by a leaf spring flexure mount of the movable Michelson mirror and by restricted alignment devices.     

A new stabilization system for optically pumped cw far infrared lasers

A new type of stabilization system for optically pumped far infrared (FIR) lasers based on a dual modulation technique is described, which enables to control the laser output power both as a function of the CO₂-laser pumping frequency and the FIR laser cavity length. The system greatly improves the laser output stability and causes only a negligible modulation (<1 %) of the output power. An additional feature, an electronic search circuit for emission lines, simplifies working at the laser even by ineperienced people.     

非对称针尖结构对远红外超材料谐振性能的影响研究

为提高远红外超材料的品质因子Q和检测灵敏度,本文研究了一种用于金属远红外超材料的非对称针尖设计。以传统双开口方形谐振环为模型,通过理论模拟,研究了开口狭缝针尖角度变化对其电场分布、谐振频谱以及品质因子Q的影响。结果表明,非对称针尖增强了谐振环的表面电场局域性,减小了谐振峰的半峰宽,并使品质因子Q提高到传统谐振环（非针尖设计）的三倍以上。该研究结果为开发高灵敏远红外超材料传感器提供了新的思路,并为传统开口谐振环提出了一种简单实用的Q因子优化方法。     

High resolution far infrared polarimeter for plasma diagnostics

A method for the Faraday rotation angle measurement in RFX is described, which does not require an interferometric structure, resulting in a considerable simplification of the diagnostic apparatus. It incorporates the same principle of operation as is employed in a high resolution polarimeter for visible wavelengths. The test on the bench performed at the Far Infrared wavelength of interest (λ=118.8 μm) is described, the results which were obtained are presented and discussed, and the feasibility of the method has been clearly demonstrated.     

Dielectric waveguide for middle and far infrared radiation

The possibility of using the normal skin effect in dielectric waveguides for long-wavelength radiation is analyzed. A design of a waveguide integrated with a heterolaser is suggested, in which an undoped layer of GaAs is clad between heavily-doped n- and p-Al _x Ga_{1 ? x} As alloy layers, reflecting radiation because of the normal skin effect. It is shown that an efficient waveguide can be formed using n-Al _x Ga_{1 ? x} As layers with x < 0.45 and the electron concentration N > 5 × 10¹⁸ cm^?3 and p-Al _x Ga_{1 ? x} As layers of any composition with the hole concentration P ≥ 3 × 1019 cm^?3.     

Modes of a tilted-mirror optical resonator for the far infrared

In an extension of the work of A. G. Fox and T. Li of Bell Telephone Laboratories, a study was made of the modes of tilted-plane mirrors having enough tilt to use the spillover radiation (at a straight edge) as output coupling. This geometry seems desirable as an oscillator to intercept a molecular beam and extract coherent power in the far infrared. Control of the tilt angle provides variableQ. Amplitude and phase of the output are smooth enough to use cylindrical optics for focusing or collimating the output. The three lowest-order two-dimensional modes were studied which, under reasonable conditions, are determined by a single parameter. It isbeta = alpha(b/lambda)^{1/2}, where α = mirror tilt, b = mirror separation, and λ = wavelength. The lowest mode (TEM0) has loss per pass that increases almost linearly from 3 percent atbeta = 10^{-2}to 37 percent atbeta = 10^{-1}. The output appears to diverge from a virtual source about 3b behind the spillover edge of the shorter mirror. The virtual source of the lowest mode is displaced (0.7 to 1.1)(lambda b)^{1/2}inward from the spillover edge. The mathematical problem proved to be an interesting exercise in devising ways to isolate an eigenfunction of an integral operator when the eigenvalues are nearly equal.     

一种多尺度远红外夜间交通行人识别方案

为降低夜间行车导致交通事故的概率,在能见度不理想的行车环境中为车辆提供主动安全系统,依据汽车辅助驾驶系统的基本要求,基于远红外传感技术,设计出夜间行人辅助模型。该模型通过远红外传感器来捕捉原始的数据源,利用灰度统计技术获取ROIs,构造出多尺度概率模板,在此基础上对数据源进行匹配检测,通过多帧校验综合处理技术将模型的漏检率和检测率进一步改善。实验表明,该模型的概率模板在匹配精度上相对于业内常用方法有了较大程度的改善,此外该模型还能够在郊区和市区两种交通路况下使用,实用性较好。     

A dual doubly curved reflector antenna having good circular polarization characteristics

A new type of shaped-beam radar antenna having good polarization characteristics is described. This antenna is composed of a dual doubly curved reflector system and a feed horn with good axial ratio, such as a dual-mode horn. The rotationally symmetrical beam of the feed horn can be converted into a shaped beam by the reflector system without degradation of the axial ratio. The design of this type antenna is discussed and the experimental results of a model antenna with a cosecant squared beam are shown. Integrated cancellation ratio of the model was 22 dB.     

Determination of the spectral width of Raman gain regions for different far infrared laser gases using a metal mesh Fabry Pérot interferometer

In this paper we report on the determination of the spectral width of Raman gain regions for different far infrared laser gases using a metal mesh Fabry Pérot interferometer. By use of broadband pump radiation emitted from a high pressure CO₂ laser we generated far infrared radiation within the Raman gain regions via stimulated Raman scattering. The spectral width of the far infrared radiation was determined using a Fabry Pérot interferometer in high interference order. We applied the method to study stimulated Raman scattering in D₂O and methylfluoride at different gas pressures.     

移相式泰曼-格林红外干涉仪及应用

研究了移相式红外泰曼-格林干涉仪，研制出光机电算一体化的仪器，仪器孔径为Φ30mm。编制了计算机软件，用于干涉图波面的拟合与红外光学系统成像质量的评价，所鳊软件与国际上同类软件的计算精度相当。介绍了红外干涉仪的多种应用：评价红外光学系统的像质，检测光学件精磨表面粗糙度、光盘基片面形的平整度。结果表明，仪器干涉系统光学质量优于λ／25，扩展不确定度优于λ／130，重复性优于λ／200(λ=10．6μm)。