The Optimum Operation of an Unified Mini-Optically Pumped NH3 Submillimeter Wave Laser

An unified miniature optically pumped NH₃ submillimeter wave laser (OPSMMWL), including a mini TEA-CO₂ pump laser, was developed. It lased successfully with coherent emission at 67.2m, 90.4m and 151.5m. The optimum operation of the unified mini-OPSMMWL was studied experimentally and the relations among SMMW laser output power, operating gas pressure, length and coupling condition of the cavity were measured. It has been found that buffer gas N₂ has significant effect on 67.2m and 151.5m emissions and very wide band SMMW laser emission was a common feature of the mini-OPSMMW cavity laser.     

Theoretical Study on the Gain and Tuning Characteristics of Miniature Optically Pumped NH3 Submillimeter Laser

The gain and the tuning characteristics of miniature optically pumped super-radiant NH₃ submillimeter-wave gas laser have been studied theoretically based on the quantum density matrix equations. The density matrix equations of three-level quantum system have been solved, and the gain and the output density versus different frequency detuning of submillimeter laser and infrared pumping laser have been calculated respectively by means of iteration method. The characteristic curves corresponding to ideal monochromatic IR pumping model and broadened IR pumping model have been obtained. Meanwhile, the tuning and the nonlinear properties of the system have been revealed.     

Operating Parameters Optimization of Buffer Gas in Optically Pumped Submillimeter Wave Laser

Based on the basic theory of molecular vibration relaxation and semi-classical density matrix theory, operating parameters optimization of buffer gas in the process of miniature pulsed optically pumped submillimeter wave laser was systemically studied and the theoretical calculated result was tested by experiments. The result would do favor to develop and study high-power and wide-range tunable miniature and high-efficient pulsed optically pumped submillimeter wave laser and also had some instruction to its application.     

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.     

Multi-Raman Processes and Their Effects in Two-Longitudinal-Mode Optically Pumped Submillimeter Wave Laser

Based on the semi-classical density matrix theory, multi-Raman processes in two-longitudinal-mode optically pumped cavity submillimeter wave laser were studied theoretically. And their effects on submillimeter wave laser spectral characteristics were discussed under different pump powers, operating pressures and laser tube lengths.     

Multi-Raman Effect and Longitudinal-Mode Structure in Optically Pumped Submillimeter Wave Laser

Based on semi-classical density matrix theory, multi-Raman interaction in multi-longitudinal-mode CO₂-9R (30) optically pumped NH₃ molecules laser was studied theoretically. With different parameters such as pumping power and operating gas pressure, the effect of multi-Raman interaction and the longitudinal-mode structure of submillimeter wave laser were also discussed.     

Temperature and Mass Factor of Buffer Gas Effect in Optically Pumped Submillimeter Wave Laser

Based on semi-classical density matrix theory and SSH theory, the effect of buffer gas in optically pumped submillimeter wave laser was theoretically studied and the effect of temperature and mass on the effect of buffer gas was analyzed, then the selection rules of buffer gas were achieved. The results could do favor to find high-efficient buffer gas of miniature optically pumped submillimeter wave laser and also had some instruction to its application.     

Energy Exchange Process in Two-Longitudinal-Mode Optically Pumped Submillimeter Wave Laser

Based on the semi-classical density matrix equations and numerical iteration calculation, the gain coefficient of nine-energy-level NH₃ molecular system was figured out. Energy exchange process in two-longitudinal-mode optically pumped submillimeter wave laser was studied in detail. Laser output intensity was calculated and discussed in case of different operating parameters such as operating gas pressure, length of laser cavity. Finally the optimization rules were concluded.     

A New Model of Calculating Miniature Optically Pumped Far-Infrared Laser

Considering the broadening of infrared pumping laser, the spectrum of miniature optically pumped superradiant NH₃ far-infrared laser pumped by CO₂-10R(8) has been calculated by solving density matrix equations and using iteration method. It is first time that the theoretical spectrum has been in good agreement with experimental results.     

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.     

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.     

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.     

Theoretical study of multi-mode optically pumped NH3 FIR laser

The two or multi-mode optically pumped NH₃ FIR laser had been studied theoretically. The NH₃ molecular gas was assumed to be a three-level system and obeyed the time-dependent behavior of the density matrix equations. Considering the situation of playing the two or multi-mode optical pumping and the FIR laser field were same polarized. The gain coefficient and the output FIR power of the system could be calculated by using the iteration method.It had been predicted that the two or multiple longitudinal mode optically pumped NH₃ FIR laser could have a greater output power or higher lasing efficiency than single mode pumped FIR laser under suitable selected operating parameters of laser.Supported by The Education Foundation of PRC.     

The Current Development of Far Infrared Technology

The research development and the latest results of far-infrared laser in the last few years were introduced from the following aspects: far-infrared laser, study of basic science, study of astrophysics, communication and military applications, engineering applications, study of medical biology and other applications.     

Theoretical study of miniature optically pumped cavity NH3 Far-infrared laser

Miniature optically pumped cavity NH3 Far-infrared laser was studied theoretically, with the length of the FIRL cavity as short as 1.5cm, the dependences of FIRL output power and laser lineshape on operating gas pressure and output coupling condition, and on the effect of laser line saturation broadening were calculated.Supported by the National Natural Science Foundation of China.     

Experimental Study of Pulsed Optically Pumped Superradiant and Cavity NH3 Far-Infrared Laser

Using a grating tuned TEA-CO2 laser with 10R(8) and 9R(16) line to pumped superradiant NH3 far-infrared (FIR) laser which operated in the mode of amplified stimulated emission and Fabry-Perot cavity NH3 FIR laser with a sample tube of 100cm and 20cm in length respectively, the corresponding pulsed FIR lasers were obtained successfully. Meantime, the experimental measure method was improved. Besides, the operating performance and the spectral characteristics of superradiant and cavity NH3-OPFIRL were studied experimentally.     

980nm OPS-VECSEL关键参数的理论分析

光抽运半导体垂直外腔面发射激光器(Optically Pumped Semiconductor Vertical External Cavity SurfaceEmission Laser)的输出特性受到诸多参数的影响,理论分析和模拟显得尤为重要.设计了一种以808 nm二极管激光耦合模块为光抽运光源,In_0.159Ga_0.841As/GaAs_0.94P_0.06为增益介质的980 nm光抽运垂直外腔面发射激光器,并借助于PICS3D软件计算了器件各种特性参数.分析了芯片半径、量子阱的周期数以及外腔镜反射率对器件性能的影响,特别是对阈值和光-光转换效率的影响.模拟结果表明,器件的半径影响光-光转换效率.量子阱个数和外腔镜反射率对器件的输出功率和光-光转换效率都有影响,所以要根据实际需要,设计、生长结构和进行实验.     

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.     

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.     

Spectra of optically pumped superradiant and cavity NH3 far-infrared laser

Based on the density matrix theory of quantum system, the spectra of optically pumped superradiant and cavity NH₃ far-infrared (FIR) lasers were calculated by means of iteration method. The calculation showed that, compared with the optically pumped superradiant FIR laser, the cavity laser had a wider band spectrum of FIR emission and a higher output power under certain condition, moreover, the spectra of cavity laser had multi longitudinal-mode structure. Supported by the Research Foundation of Hubei Province Education Committee, PRC