Theoretical Study on NH3 Superradiant Miniature Optically Pumped Far-Infrared Laser with Buffer Gas

A miniature superradiant NH₃ optically pumped far-infrared laser (OPFIRL) with buffer gas N₂ was theoretically studied. Base on the mechanism model of buffer gas, synthetical relaxation time was calculated. By solving the semi-classic density matrix equations, spectra of NH₃ superradiant OPFIRL with buffer gas N₂ was calculated, also the operating gas pressure. It was found that by adding buffer gas, FIR power could be raised, and there existed an optimum ratio of gases mixture and an optimum operating gas pressure which was higher than that of pure NH₃ operating.     

Operating Parameter Comparison of Pulsed Optically Pumped NH3 and CH3OH F-P Cavity Far-Infrared Laser

Based on the density matrix theory of quantum system, the optimum operating parameters of pulsed optically pumped NH3 and CH3OH F-P cavity far-infrared laser (NH3/CH3OH-OPFIRL) were studied and compared theoretically. The differences of the operating parameters between the NH3-OPFIRL and CH3OH-OPFIRL were found and discussed. Experimentally, the curves of output power verses gas pressure in NH3 and CH3OH F-P cavity lasers pumped by TEA-CO2 laser were measured, and the optimum operating gas pressure were obtained. The experimental results were in agreement with theoretical calculations.     

The Optimum Coupling Coefficient of Optically Pumped NH3 Far-Infrared Cavity Laser

Based on the semiclassical density matrix theory, the optimum output power reflection coefficient (coupling coefficient) of output coupler for optically pumped NH₃ far-infrared (FIR) cavity laser was calculated by means of iteration method. Experimentally, FIR Fabry-Perot cavity laser was designed and constructed by using inductive metallic meshes as couplers, and the measurement showed that the theoretical calculation were in agreement with experimental results.     

Spectral Characteristics Comparison of Pulsed Optically Pumped NH3 and CH3OH Far-Infrared Laser

By solving the density matrix equations of a quantum system, the output power intensity of pulsed optically pumped NH3 and CH3OH far-infrared laser (OPFIRL) was calculated respectively by means of iteration method. Based on the calculations, the spectral characteristics of pulsed NH3-OPFIRL and CH3OH-OPFIRL were studied and compared theoretically. The differences of spectral characteristics between the NH3-OPFIRL and CH3OH-OPFIRL were found. Experimentally, a series of FIR emissions of NH3 and CH3OH cavity lasers pumped by TEA-CO2 laser were measured, and the experimental results were in agreement with theoretical calculations.     

小型光泵腔式NH3分子亚毫米波激光器的实验研究

实验上采用金属网栅耦合的小型Ｆ－Ｐ腔式ＮＨ３分子激光器,用ＴＥＡ－ＣＯ２激光器的１０Ｒ（８）谱线作为泵浦,获得了２８１μｍ的亚毫米激光,并对该激光器工作参数的优化进行了系统的实验研究。     

Effects of Buffer Gas on the Output of Optically Pumped NH3 Far-Infrared Cavity Laser

By solving the semi-classical density matrix equations and developing a buffer gas mechanism model, the effects of buffer gas on the output power of optically pumped NH₃ far-infrared cavity laser were calculated and verified by experiment. Our results showed that: the output power of NH₃ far-infrared laser could be increased when certain buffer gas was added into the laser medium, and there existed an optimum ratio of gases mixture and an optimum operating gas pressure which could make the output power of far-infrared laser reach maximum.     

Theoretical Study of Optically Pumped NH3 Far-Infrared Laser in Vibrational Ground State

In this paper, the density matrix equation of three-level system for far-infrared (FIR) Raman transition in vibrational ground state was solved. By means of iteration method and numerical calculation, the spectral characteristics of NH₃ molecules FIR laser with TEA CO₂-10R(14) laser pumping was studied theoretically. The theoretical result would help us to understand the physical mechanism of optically pumped molecular gases FIR laser with ground-state reversal transition.     

Energy Exchanged Process of Superradiant Optically Pumped Far-Infrared Laser with Buffer Gas

By means of solving the density matrix equations, base on the mechanism model of buffer gas, the output intensity of FIR and the FIR signal gain coefficient Gs and IR pumping signal absorption coefficient Gp were calculated, energy exchanged process of superradiant OPFIRL with buffer gas was analyzed. It was found that after adding buffer gas into the laser medium, the FIR output could be increased, and the active region of a FIR laser was lengthened.     

光泵腔式远红外激光器的工作参数研究

在研究光泵腔式NH3分子远红外激光频谱特性的基础上，应用量子系统的密度矩阵理论，采用迭代法和增益迭加原理计算了以TEA CO2－10R（8）泵浦的NH3分子腔式远红外激光器的最佳工作参数。提供了光泵腔式NH3分子远红外激光器（腔式NH3－OPFIRL）的工作参数之间的关系曲线。     

光泵腔式NH3分子亚毫米波激光的调谐特性研究

通过求解量子系统的密度矩阵方程，计算了不同管长和不同输入输出功率反射系数的光泵腔式激光器对281um和90.4um的亚毫米波信号的调谐特性，给出了其调谐特性随信号波长λ，激光管长l和功率反射系数R的变化关系。     

An Optically Pumped Far-Infrared Folded Mirror-Less Cavity

A compact and efficient mirror-less cavity is presented for an optically pumped 192-μm far-infrared laser. With a gold-coated mirror and 30°-inclined anti-reflection coated Ge plate serving as highly reflective mirrors, a folded mirror-less CH₃F cavity is achieved. Maximum energy of 0.72 mJ is obtained with the pump energy of 600 mJ, which gives an energy increment of 75% in comparison with the previous 1.85-m mirror-less system. The beam divergence angle of the FIR radiation from this folded mirror-less cavity is measured to be 14.2 mrad.     

Effects of Buffer Gas on Spectra of Optically Pumped Far-Infrared Cavity Laser

By developing a mechanism model of buffer gas, the comprehensive relaxation time of laser operation substance was calculated. By means of solving the density matrix equations, the effects of buffer gas N₂ on the spectrum characteristics of NH₃ FIR laser line with buffer gas N₂ were studied. It was found that by adding proper buffer gas, FIR laser output power could be increased, and spectra widened because of the molecular collision. This work made it possible to develop high output and wide range tunable FIRL.     

Effect of Multi-Mode Optically Pumped Far-Infrared Laser Cavity on Spectra and Multi-Raman Interaction

Based on semi-classical density matrix theory, the spectral characteristics and multi-Raman interaction of multi-longitudinal-mode CO₂-9R(30) optically pumped cavity NH₃ molecules 67.2 μ m far-infrared laser were theoretically studied. And with different parameters such as input and output reflection coefficient, length of tube and so on, the rules of multi-Raman interaction and effect on longitudinal structure of 67.2 μ m far-infrared laser spectrum were also discussed theoretically.     

Study on Stark Effect in Optically Pumped Far-Infrared Laser

The output intensity of optically pumped NH3 molecules far-infrared laser (NH3-OPFIRL) was calculated by solving the density matrix equation and by means of iteration method. Meanwhile, the spectral characteristic of AC Stark splitting was studied. Finally, the F-P interferogram of NH3-OPFIRL pumped by CO2-10R(8) line was measured. The experimental results were in good agreement with the theoretical calculation results.     

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.     

Operating Parameters Optimization of Miniature Optically Pumped Cavity NH3 Submillimeter Wave Laser

By means of the iteration method, the output power density of the miniature optically pumped NH₃ submillimeter wave (SMMW) laser was calculated based on the density matrix equations of a quantum system. Optimization of operating parameters including operating gas pressure, reflection coefficients of input and output meshes of the laser were studied systematically. In the paper, the concepts of the average activated length and the synthetical optimum value were defined, and some rules of the optimization were explained successfully. Experimentally, a cavity NH₃ SMMW laser that was composed of a pair of inductive metallic meshes and pumped by TEA-CO₂ 10R(8) line was used. The experimental results were in good agreement with our theoretical calculations.     

缓冲气体对光抽运远红外激光器频谱特性的影响

基于分子振动弛豫理论完善了缓冲气体的作用模型，利用半经典密度矩阵理论与量子力学理论，定量分析研究了缓冲气体对小型光抽运远红外激光过程的作用机理以及缓冲气体作用下小型腔式光抽运NH3分子远红外激光器的频谱特性，讨论了工作气压、抽运功率等工作参数对频谱特性的影响，并对理论计算结果进行了实验验证．二者符合得较好。研究结果表明，在小型光抽运远红外激光器中加入适当的缓冲气体，大量工作气体分子与缓冲气体分子之间的无规碰撞会引起谱线加宽，而且可以使远红外激光输出信号增强。     

A Revisory Mathematical Model on Optically Pumped Far-Infrared Laser

In an optically pumped far-infrared laser (OPFIRL) system, the infrared (IR) pumping laser with collision broadening which was closer to the practice was considered. A more precise mathematical model was set up. When the IR pumping laser line had the Lorentz function structure, by solving the semi-classic density matrix equations, the generalized form of FIR signal gain Gs and IR pumping signal absorption coefficient Gp were obtained.     

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。     

Study on the Spectrum of Miniature Optically Pumped NH3 Submillimeter-Wave Laser

By means of an iteration method and taking into account the broadening of the infrared pumping laser, the spectrum of a miniature, optically pumped, superradiant NH₃ submillimeter-wave(SMMW) gas laser pumped by CO₂-10R(8) has been calculated and studied by solving density matrix equations. Experimentally, the interferogram of miniature SMMW laser pumped by a TEA-CO₂ laser with 10R(8) line is measured. This is the first time that the theoretical spectrum has been in good agreement with experimental results.