基于差频中红外激光的痕量气体高分辨光谱检测研究

研究了基于差频光源的高分辨中红外激光光谱检测系统,差频中红外光源使用两台近红外半导体激光器作为种子光源,采用PPLN晶体作为非线性混频器件,结合准相位匹配技术实现了3.2～3.7μm中红外相干光源输出,最大差频输出功率约为1μW.以CH4为例检验了系统的高分辨红外光谱检测特性,选择CH4分子3028.751cm-1 v3基频吸收线作为分析谱线,10cm光程的检测限为0.8ppm.光谱数据分析表明,系统检测限主要受到标准具光学噪音的限制.     

真空条件下低温红外辐射测量技术研究

针对红外载荷在轨服役期间低温目标的红外辐射探测需求，提出一种真空条件下的低温红外辐射测量方案，并研制了测量装置。测量装置主要由低温红外光学系统、低温机械结构、低温红外探测系统及微弱信号处理系统构成。低温红外辐射经过光学系统会聚到探测器像面，锁相放大器利用相干检测技术将目标信号提取，完成低温红外辐射的测量。测量装置研制完成后，在真空仓内使用标准黑体辐射源，在198 K～423 K温度范围内进行了低温红外辐射定标试验，取得了有效的试验数据，测量不确定度在5%以内。该文提出的真空条件下低温红外辐射测量技术可为在轨空间红外载荷低温红外目标探测设计提供重要数据支撑。     

连续波光参量振荡器定向红外干扰

介绍了基于光纤激光器泵浦的光学参量振荡器发展现状及其在定向红外干扰技术中的应用前景,对定向红外干扰技术的一些基本原理进行了讨论。利用自研的一台基于光纤激光器泵浦的连续波光学参量振荡器,通过周期调谐的方式分别实现3.414,3.630和3.820 m的瓦级中红外激光输出。采用这3个波长的激光对中红外热像仪进行了干扰原理性实验。对比实验结果可以得出:对于3.820 m波长的中红外激光,当其辐照的HgCdTe探测器前功率密度大于10 W/cm2量级时,在传输750 m距离后,热像仪实现饱和效果并且非饱和区域图像灰度级发生较大变化,达到了掩盖有用信号的目的。     

Intracenter Raman silicon lasers

Raman-type Stokes stimulated emission in the far-infrared wavelength range (52–65 μm) has been realized in silicon crystals doped by group-V hydrogen-like donor centers at low temperatures under optical excitation by radiation from a pulsed frequency-tunable infrared free-electron laser. The light scattering appears as an entire intracenter process and occurs on the donor electronic transitions being resonant to the intervalley transverse acoustic g phonon. The outgoing and incoming electronic donor resonances amplify the efficiency of scattering, so that the Raman optical gain increases to the values observed for the infrared room temperature Raman silicon lasers.     

基于微机电系统红外光源的长光程气体检测

针对红外气体传感器对光源的要求,选用了一种宽波长、高调制频率、低功耗的小体积微机电系统(micro-electro-mechanic system, MEMS)红外光源作为辐射源,其各项性能均能很好的满足红外传感系统对于光源的要求。由于其面光源的朗伯辐射特性,整形之后的红外光数值孔径仍然很大,采用传统的长光程气室结构很难实现长光程从而提高系统的检测灵敏度。本文结合双波长单光路的差分检测方法,设计了一种基于积分球特性的吸收气室,有效地解决了MEMS红外光源在高灵敏度气体检测应用中难于实现长光程的问题;并运用光在传输过程中光通量守恒的原理,推导了此积分球吸收气室的等效光程,解决了积分球气室等效光程计算的难题;同时采用FPGA主控芯片对MEMS红外光源进行高频调制并处理探测器的输出信号,使得外围电路的设计更加简单、灵活。设计中,使用直径为5 cm的积分球吸收气室便可实现166.7 cm的等效光程,研究结果显示系统可测得的最小甲烷浓度达0.001×10-6,极大地提高了红外检测系统的灵敏度。     

微波电真空器件用热阴极的温度测量

利用红外测温仪、光学测温仪、热电偶测温仪(铂铑-铂)对微波电真空器件用浸渍阴极表面、覆膜阴极表面、阴极侧面（钼筒）进行了温度对比测试研究。结果表明:采用红外测温仪和光学测温仪测试浸渍阴极表面的温度与采用热电偶测温仪测试的温度相差不大,而覆膜阴极却相差约50 ℃;采用红外测温仪和光学测温仪测试阴极侧面（钼筒）的温度相差不大,都低于热电偶测温仪测试的温度约60 ℃,这说明红外和光学测试温度值低于阴极的实际温度（热电偶测量值）。由于在阴极表面出现了物理、化学变化,红外测温仪和光学测温仪测试的阴极表面温度值在1150 ℃左右加热100 min内增加约30 ℃。分析认为这些差异主要是因为覆膜阴极的表面与浸渍阴极的表面及阴极侧面（钼筒）的发射系数不同造成的,当然测试结果也会随着这些因素的变化而有一定的变化。     

Quadratic detection with two-photon quantum well infrared photodetectors

Two-photon quantum well infrared photodetectors (QWIPs) involving three equidistant subbands take advantage of a resonantly enhanced optical nonlinearity, which is six orders of magnitude stronger than in a bulk semiconductor. This approach results in a sensitive device to measure quadratic autocorrelation of mid-infrared optical pulses from modelocked quantum cascade lasers, nonlinear optical conversion, and free-electron lasers (FEL). We report on autocorrelation measurements at wavelengths in the mid-infrared and Terahertz regimes using ps optical pulses from the FEL at the Forschungszentrum Dresden Rossendorf. In particular, quadratic detection at wavelengths around 5.5 μm is still possible at room-temperature, which is crucial for applications in practical systems. We also report on a two-photon detector which works below the Reststrahlen band at 42 μm (7.1 THz).     

高功率掺镱光纤激光器的辐照影响分析及研究进展

高功率掺镱光纤激光器在空间环境中的应用日益增多,但掺镱光纤材料在空间辐照条件下会产生色心效应,导致损耗增加,影响光纤器件以及激光器整机的性能,从而给高功率光纤激光器在空间环境的长期稳定工作带来隐患。从空间辐照对高功率光纤激光器性能的影响机理、抑制方法和研究进展等3个方面进行介绍。首先介绍了空间辐照对高功率掺镱光纤激光器中关键光学器件、放大级热负载、非线性效应等方面的影响分析,其次介绍了抑制辐照效应的典型方法及其在高功率掺镱光纤激光器中的可行性分析,最后介绍了国内外典型的高功率掺镱光纤激光器的辐照影响及抑制的研究成果,并展望了未来发展趋势。     

Manufacturing of Nd:Gd3Ga5O12 ridge waveguide lasers by pulsed laser deposition and ultrafast laser micromachining

Laser radiation is used both for the deposition of the laser active thin films and for the micro structuring to define wave guiding structures for the fabrication of waveguide lasers. Thin films of crystalline and amorphous neodymium doped Gd₃Ga₅O₁₂ are grown on single crystal yttrium aluminium garnet by pulsed laser deposition using excimer laser radiation.Manufacturing of the laser active waveguides by micro structuring is done using femtosecond laser ablation of the deposited films. The structural and optical properties of the films and the morphology of the structured waveguides are determined in view of the design and the fabrication of compact and efficient diode pumped waveguide lasers. The resulting waveguides are polished, provided with resonator mirrors, pumped using diode lasers and the waveguide lasers are characterized. The spectroscopic properties of the amorphous waveguide are investigated and an infrared waveguide laser is demonstrated. To our knowledge, there have been no reports by other groups of the successful operation of a structured waveguide laser fabricated by this technique or of a waveguide laser made from amorphous neodymium doped Gd₃Ga₅O₁₂.     

Simple eye-safe lidar for cloud height measurement and small forest fire detection

A simple and robust eye-safe lidar was developed on the basis of a rangefinder optical scheme comprising an Er:glass laser which generates 8 mJ pulses of 1540-nm radiation with the pulse repetition rate of 0.17 Hz and a 38-mm-diameter telescope. Reliable measurements of the cloud height up to 3700 m and early forest-fire detection with a range of 3000 m were experimentally demonstrated. Theoretical estimations indicate that using an optical scheme built around a 10 Hz Er:glass lasers and 150 mm light gathering optics early forest fire detection in a range up to 6500 m can be achieved.     

中红外光学参量振荡器技术进展

3~5μm中红外激光器在环境污染检测、医疗、工业等领域具有重要的应用价值。本文总结了基于ZnGeP_2、MgO∶PPLN晶体的光参量振荡器(OPO)的国内外发展现状,分析了其各自不同结构系统设计的优势和发展前景。指出高功率、小体积、轻重量的光学参量振荡器是未来重要发展方向,发展的技术核心是生长更大尺寸的中红外激光晶体以及研制更高性能指标的OPO泵浦源,并对中红外激光器的发展趋势进行了展望。     

Infrared particle detection for battery electrode foils

Failures of electrochemical cells caused by internal shorts still are an important issue to be faced by the cell manufacturers and their customers. A major cause for internal shorts are contaminated electrode foils. These contaminations have to be detected securely via a non-destructive inspection technique integrated into the electrode manufacturing process. While optical detection already is state of the art, infrared detection of particles finds a new field of application in the battery electrode manufacturing process. This work presents two approaches focusing on electrode inspection by electromagnetic radiation (visible and infrared). Copper foils with a carbon based coating were intentionally contaminated by slivers of aluminum and copper as well as by abraded coating particles. Optical excitation by a flash and a luminescent lamp was applied at different angles in order to detect the reflected visible radiation. A laser impulse was used to heat up the specimen for infrared inspection. Both approaches resulted in setups providing a high contrast between contaminations and the coated electrode foil. It is shown that infrared detection offers a higher security thanks to its reliance on absorbance and emissivity instead of reflectivity as it is used for optical detection. Infrared Detection offers a potential since it is hardly influenced by the particle’s shape and orientation and the electrode’s waviness.     

Principles and performance of an electron spin echo spectrometer using far infrared lasers as excitation sources

We have built an electron spin echo spectrometer operating at 604 GHz, extending the frequency limit of existing spectrometers by more than a factor of 4. In order to handle this high frequency we have used optical techniques, i.e., molecular gas lasers for the excitation pulses and far infrared techniques for the heterodyne detection system. The different components of the spectrometer are described in detail and first experimental results are given.     

Aperiodic birefringent photonic structures based on Kolakoski sequence

A novel type of aperiodic porous silicon-based multilayered structures which can be used for the electromagnetic radiation manipulation in the visible and infrared parts of spectrum are proposed in this paper. The one-dimensional aperiodic structures under consideration are arranged by stacking together two anisotropic layers according to the Kolakoski self-generation scheme. The spectral properties of the structures are theoretically investigated by using the electromagnetic field scalarization method in coupling with the finite-difference method. It is shown that the Kolakoski multilayers have both completely transparent states in the transmission spectra and pronounced omnidirectional reflectance which can used in integrated optics, optical fiber telecommunications, vertical cavity surface emitting lasers, laser cavities, etc. Also, it is shown numerically that the anisotropic nature of layered media significantly affects on optical properties of the structures.     

低温真空红外傅里叶光谱仪噪声等效辐亮度定标系统

红外傅里叶光谱的等效噪声辐亮度(NESR)是反映其对红外目标信号的极限探测能力,也是仪器的主要技术指标。受限于我国当前的技术条件,尚无相关能力的测试定标系统和检定规范。通过借鉴当前国内外的红外辐射计量装置的标准传递思路,提出了一种NESR高精度测试装置方案。给出了该装置的溯源链路,描述了其整体和光路结构,并设计了低温真空背景抑制模块。着重介绍了宽动态范围红外积分球辐射源设计、等效光路设计和真空低温环境模块等设计方案。提出的设计方案为NESR高精度测量提供基本的参考依据,为我国傅里叶光谱的NESR的量值溯源提供支撑条件。     

弹道导弹再入段地面红外探测仿真分析

为改善弹道导弹再入段地面红外探测效果,考虑导弹再入过程中气动加热、红外辐射的大气衰减以及背景辐射等因素,建立起弹道导弹再入段地面红外探测仿真分析模型,并估算分析了探测系统在不同状况下信噪比.分析结果表明：优选工作波段、增加系统口径及曝光时间、改善光学设计、选择晴朗无云天气观测等均有利于改进地面红外观测效果.     

Autocorrelation measurements of free-electron laser radiation using a two-photon QWIP

The two-photon QWIP comprises three equidistant subbands, namely two bound states localized in the quantum well and an extended state in the continuum. This device is very promising for quadratic autocorrelation measurements of pulsed mid-infrared lasers due to its resonantly enhanced optical nonlinearity and sub-ps time resolution. We report on interferometric autocorrelation measurements of ps optical pulses from a free-electron laser (FEL). The intense FEL radiation further allows us to study the saturation properties of two-photon QWIPs at liquid nitrogen temperature and their detection properties at 300 K. The device is well suited for standard diagnostics of the FEL pulse shape via interferometric autocorrelation.     

Parametric interaction and backward wave oscillation in stimulated compton scattering

Stimulated Compton-Raman scattering and free electron lasers are formulated as parametric (four-photon) or three-wave interaction processes. Manley-Rowe relations and depletable pump equations are derived for both free electron lasers and optical klystron schemes. A process of backward wave oscillation is predicted when a pump radiation field is back scattered off a codirectionally propagating e beam with frequency down conversion. A practicable experiment in the optical regime is proposed to demonstrate this effect.     

Infrared laser based on the principle of melt crystallization or vapor condensation. Why not?

The paper discusses a possibility of new effects in quantum electronics: amplification of certain frequency infrared beams in supersaturated vapors or super-cooled melts as well as design of infrared lasers based on a new type of pumping. The basis of these effects is the existence of characteristic infrared radiation accompanying phase transitions of the first order, especially crystallization and condensation. Experimental results of the author and other researchers concerning characteristic infrared emission detection during crystallization from the melt of some substances (alkali halides, sapphire, tellurium, ice, etc.) are presented, as well as condensation of water vapor. The author has critically analyzed these experimental data in terms of correspondence to the theoretical models. The last ones are based on the assumption that the particle (atom, molecule or cluster), during transition from higher energetic level (vapor or melt) to the lower energetic level (crystal), emits one or more photons depending on the latent energy of the transition. Based on the experimental data, the author postulates a transparency window appearance for the characteristic radiation in the substances where first-order phase transitions take place.     

基于差频中红外激光的痕量气体高分辨光谱检测研究

研究了基于差频光源的高分辨中红外激光光谱检测系统,差频中红外光源使用两台近红外半导体激光器作为种子光源,采用PPLN晶体作为非线性混频器件,结合准相位匹配技术实现了3.2~3.7 μm中红外相干光源输出,最大差频输出功率约为1 μW.以CH₄为例检验了系统的高分辨红外光谱检测特性,选择CH₄分子3 028.751 cm^-1 v₃基频吸收线作为分析谱线,10 cm光程的检测限为0.8 ppm.光谱数据分析表明,系统检测限主要受到标准具光学噪音的限制.