远红外激光的研究进展

就提高远红外激光光束质量、探讨新的微观机理和探索新现象三个方面介绍了近年来远红外激光的研究进展和最新研究成果。     

用远红外HCN激光干涉仪测量等离子体电子密度

在大多数托克马克上，远红外激光干涉仪是等离子体诊断中的一种重要的装置。本文介绍了用远红外ＨＣＮ激光干涉仪测量等离子体电子密度的原理和激光干涉仪结构，并给了了首次在我国第一以大型超导托克马克ＨＴ－７装置上测到的中心弦等离子体电子平均密度。     

超小型光泵远红外激光研究

在求解NH_3分子三能级系统密度矩阵的基础上,用迭代法计算了长为10cm—1.5cm的5支超小型光泵远红外激光器(OPFIRL)的输出激光能量密度和频谱特性.实验研制的5支超小型OPFIRL成功地产生了远红外激光.研究表明:纵向腔效应和横向反馈效应对超小型OPFIRL激光输出有积极作用,对最佳工作气体压强和频谱特性有重要影响.     

远红外技术的发展近况

就远红外激光在基础学科的研究、天体物理研究、通信和军事应用、工程应用、医学生物学研究和其它应用几个方面介绍了近年来这方面研究进展和最新研究成果。     

光泵远红外激光的缓冲气体的选择因素

在半经典密度矩阵理论和SSH理论的基础上,理论研究了光泵远红外激光的缓冲气体作用,分析了势阱深度和碰撞半径两个参数对光泵远红外激光系统中缓冲气体作用的影响,从而得到选择缓冲气体的规律。研究成果对寻找小型光泵远红外气体激光器的高效缓冲气体,并推动其实际应用起一定的指导作用。     

缓冲气体对超辐射光抽运远红外激光器的影响

以NH3作为远红外激光的工作气体 ,以N2 作为缓冲气体 ,对加入缓冲气体前后的小型超辐射光抽运远红外激光器作理论比较研究。基于缓冲气体作用机理模型 ,计算出激光工作物质的综合弛豫时间 ;通过解半经典的密度矩阵方程 ,计算出远红外激光输出的频谱特性和工作气压。计算表明 ,加入缓冲气体后 ,远红外激光的输出得到提高 ;存在一个最佳混合气体比例 ,在这一比例下远红外激光输出达到最大 ;加入缓冲气体后 ,最佳工作气压比加入缓冲气体前获得提高。     

多纵模光泵远红外激光的实验研究

实验研究了多(双)纵模和单纵模光泵NH_3分子系统的远红外激光输出特性,与理论计算作了比较,结果表明:在相同泵浦总功率条件下,适当控制激光器的工作参数,两者可产生相同的远红外谱线,能保持相同的波谱质量,并有大致相同的输出功率密度。     

光泵浦远红外气体激光器的研究发展

远红外激光具有穿透性强、光子能量低、带宽宽、通信传输容量大等优点,在公共安全、环境探测、生物医学、天文观测、军事以及通信等方面得到了广泛应用。在介绍了远红外波段激光器发展的基础之上,对产生远红外激光的各种方式进行了对比分析和总结,讨论了光泵浦远红外气体激光器的技术优势,并针对近年来远红外激光工作介质及其新谱线进行了归纳。通过对连续和脉冲光泵浦远红外气体激光器发展的回顾,结合该领域的一些重点研究方向,给出了未来光泵浦远红外气体激光器的研究趋势。     

远红外激光辐照水稻育种研究——水稻生物效应

报道了远红外激光辐照水稻种子对水稻生长影响的试验研究。介绍了远红外激光辐照水稻种子的秧苗、植株生长及经济性状的实验结果。     

单、双纵模腔式光泵远红外激光器的实验研究

实验上采用可选纵模的TEA－CO2激光器作泵浦源,用CO2－9R（16）线泵浦小型腔式NHG3远红外激光器,在单、双纵模泵浦条件下均获得波长为90．4μm的远红外谱线。对单、双纵模腔式光泵远红外激光的输出特性和工作气压作了实验比较研究,发现双纵模腔式光泵远红外激光可获得更强的远红外输出,具有较低的最佳工作气压值,并可在较宽的气压范围内工作。     

Frequency measurements of optically pumped far-infrared laser lines

In this work, we report the frequency measurements of optically pumped far-infrared (FIR) laser lines. We use the heterodyne technique of mixing FIR laser radiation and microwave radiation on a metal-insulator-metal (MIM) point contact tunnel diode, to determine the FIR laser frequencies. The two FIR laser systems, consisting of CO₂ waveguide pump lasers and Fabry-Perot FIR laser cavities, and MIM diode were developed by us. To check the system, we have measured some FIR laser line frequencies previously reported in the literature. An average fractional frequency reproducibility of ±7×10^-7, between our measurements and the previous ones, permit us to use our system to measure five new FIR laser frequencies     

Spectral Characteristics of Raman Emissions from Miniature Pulsed Optically Pumped Far Infrared Laser

A miniature FIR laser with a sample-tube in 10 or 20cm length were constructed, and the laser's cavity consisted of a pair of metallic meshes, with NH3 molecules as active medium pumped by a TEA-CO2 laser, a series of FIR laser lines were observed. By taking account of the properties of the Fabry-Perot cavity and the gain characteristics of Raman transitions in the miniature optically pumped FIR laser, the spectral characteristics of the FIR laser were studied.     

High power FIR NH3 laser using a folded resonator

A compact FIR laser cavity having a couple of folding mirrors was designed. By inserting this FIR cavity into the pump TE CO₂ laser resonator, we observed 19 FIR NH₃ laser lines of which 4 new lines were included. The maximum output power was over 500 W at 90 μm.     

The generation and frequency measurement of short-wavelength far-infrared laser emissions

A significantly improved three-laser heterodyne system has been assembled to generate and measure short-wavelength far-infrared (FIR) laser emissions. Over the past several years, this system has been used to discover fifty-five FIR laser emissions, ranging in wavelength from 26.3 to 185.0 /spl mu/m. These emissions were generated by optically pumping a FIR cavity with a continuous-wave carbon dioxide laser in a X-V geometry when using either hydrazine or a methanol isotopologue as the FIR laser medium. Although heterodyne techniques can be used to measure the frequencies of these FIR laser emissions with fractional uncertainties of /spl plusmn/2/spl times/10/sup -7/, shortcomings in the previous system limited its effectiveness. Improvements made to the three-laser heterodyne system have resulted in an increase in the spectral range used to search for the beat between the known and unknown laser frequencies (an increase of up to 25 GHz) as well as an increase in the system's sensitivity (by up to a factor of 30), all without requiring the use of an additional microwave frequency source. With this improved system, the FIR laser frequencies for the recently discovered 53.9- and 90.0-/spl mu/m laser emissions generated by optically pumped CH/sub 3/OD have been measured.     

一体化的小型腔式光泵NH3分子远红外激光器

研制了包括泵浦源在内的一体化小型腔式光泵ＮＨ３远红外激光器，实验测量了输出功率、工作气体压强、腔体长度与腔体耦合条件之间的优化规律：发现了小型腔式光泵远红外激光器中普遍存在的特别宽带的激光辐射现象，这将是解决远红外激光频率大范围连续可调谐的一个新途径。     

Characterization of new FIR laser lines from CHD/sub 2/OH

In this work, we report new optically pumped far-infrared (FIR) laser lines from CHD/sub 2/OH. A waveguide CO/sub 2/ laser of wide tunability (290 MHz) was used as pump source, and a Fabry-Pe/spl acute/rot open cavity was used as a FIR laser resonator. Optoacoustic absorption spectra were used as a guide to search for new FIR laser lines. We could observe 15 new laser lines in the range from 116.4 to 401.4 /spl mu/m. The lines were characterized according to wavelength, relative polarization, relative intensity, and optimum working pressure. The transferred Lamb-dip technique was used to measure the frequency absorption transition both for the new and previously reported laser lines.     

Assignments of far-infrared laser lines in the CO-stretching state of 0–18 methanol

Far-infrared (FIR) laser and infrared pump transitions of the O-18 isotopic species of methanol have been assigned for a number of CO₂ laser pump lines with the aid of high-resolution Fourier transform spectra in the FIR and CO-stretch band regions. The structures of the FIR laser energy level systems and the transition assignments were established through the use of closed transition combination loops, which also yield improved accuracies for the FIR laser wavenumbers.     

The energy exchange and the optimum length of the sample tube of opfirl

The energy exchange between the pumping laser and FIR signal in the optically pumped FIR laser (OPFIRL) system was studied. The iteration method has been used to calculate the power density of the pumping and FIR signals at any point along the optical axis of the sample tube. It was found that the power density of the FIR signal did not always increase along the length of the laser tube. There was a maximum FIR power density at the appropriate point in the sample tube. If the distance of maximum power point from the entrance of the OPFIRL tube was taken as the length of sample tube Z_opt, the maximum FIR laser output should be obtained. This was the optimum length of OPFIRL tube. The value of Z_opt was closely related to the parameter of OPFIRL such as the pumping power density, the pumping detuning and the frequency of the FIR laser. The energy-exchange and the maximum output of the fir laser were calculated under the ideal condition.     

FIR Laser Efficiency Enhancement by Double Resonance Tuning-Detailed Analysis

In a previous paper by the author (Ref. 1), FIR laser resonators with aperture coupling were shown to have resonance effect at the frequency that could be used to enhance the efficiency of the laser. This paper studies this effect over a wide range of laser parameters such as coupling aperture, cavity length and Fresnel Number. A set of curves are given to help a FIR laser designer optimize the laser.     

New CH3OH laser lines pumped with a fine-tuned high-power CO2-TEA laser

Joule-level pulses from an etalon tuned CO₂-TEA laser with an ～ 4GHz intraline tuning range have been used to pump a large number of new CH₃OH FIR laser lines. FIR wavelength measurements, pump laser offsets which produced FIR laser lines and pump laser offsets at which CH₃OH absorption lines were observed are reported. Identifications are proposed for most of the absorption lines, and an attempt to identify the FIR laser lines is described.