Design consideration of miniature OPFIRL. II. Popt of miniature cavity OPFIRL affected by Ro

The influence of the optimum parameters of mini-OPFIRL by the output couple of laser cavity was studied theoretically. The Density Matrix treatment is applied to a three-level system for steady state. The Density Matrix equations were solved under the assumption that Is 1E–13 w/cm² equal to the actual FIR power density at any points in the sample tube. Through numerical calculations, we found that the output coupling of OPFIRL affected seriously the energy exchange between pumping signal and FIR signal the stored energy of FIR signal and the optimum operating gas pressure. These problems are important to design a practical miniature OPFIRL.Supported by national natural science foundation of P. R. C.     

Study of the spectral characteristics and the output coupling of pulse optically pumped cavity SMMW laser

The miniaturization of OPFIRL plays an important role in application of this new wavelength range of electromagnetic wave, especially in that of spaceflight where efficiency and miniature are emphasized.[1][8] So it is important to optimize the operating parameters of OPFIRL. This article will start with density matrix equations, then calculate the FIR output power density under different operating conditions by means of iteration calculation. And then parameters of the laser will be changed in order to study it's spectral characteristic of the FIR laser. We found that, working under the optimum operating gas pressure, FIF output power varies with the output coupling of the cavity OPFIRL. There is an optimum value of reflection coefficient R_o of the output window which makes the output FIR power denity and spectral characteristic of miniature OPFIRL optimum.     

The dispersion of the lasing medium and optimum length of the sample tube of OPFIRL

The dispersive characteristic of the optically pumped FIR laser (OPFIRL) system had been studied theoretically. It was found that the refractive index of the lasing medium was not a constant in the OPFIRL, and the approximate value n=1 must be corrected, otherwise, it will lead to a large error for theoretical calculation of the optimization of the operating parameters of the OPFIRL. The value of n as function of (Ip, Is, x, y, z, P) was calculated theoretically. The additional losses due to the energy exchange between the lasing system and the molecules populated in the energy levels except the appointed three-level system was estimated. The calculated optimum length of the sample tube of OPFIRL with the corrected theory was in pretty good agreement with the experimental result.Supported by national science foundation of PRC     

小型光泵NH_3分子远红外激光器的模式竞争

通过求解四能级系统的半经典密度矩阵方程，用迭代法计算了ＣＯ２－１０Ｒ（６）泵浦小型超辐射光泵ＮＨ３分子远红外激光器（ｍｉｎｉ－ＮＨ３－ＯＰＦＩＲＬ）的Ｐ支和Ｑ支跃迁输出光强的增量比。计算表明在超辐射小型ＮＨ３光泵远红外激光器中，Ｖ２ａ→ｓＰ（５，４）和ａ→ｓＱ（５，４）模式竞争结果，Ｑ支跃迁占优势，使Ｐ支被抑制。理论计算与实验结果一致     

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.     

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.     

Output characteristic of transverse feedback enhanced mini-OPFIRL

The output power of a miniature OPFIRL was affected by the reflectivity of the inner wall of the sample tube. The greater the transverse feedback enhancement, the greater the output power. There was double-peak of the operating pressure when the transverse feedback was strong enough.Supported by the Chinese Foundation of Doctorate Studies and partly Supported by the Science Foundation of University Sunyatseni     

A very short OPFIR superradiant laser

A very short OPFIR superradiant laser was studied theoretically and experimentally. The density matrix equations of a three-level quantum system for NH₃ gas was solved for the gains of the FIR signal and the IR signal in the very short OPFIRL system. The output characteristics of the OPFIR superradiant laser were calculated numercally. A curve showing the relation between the length of the sampe tube of the OFFIRL and the corresponding optimum pressure was obtained. In our experiment, a 10cm OPFIRL and a 5cm OPFIRL were constructed and operated successfully. The output characteristics were meassured and the calculated results were verified.     

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.     

Laser induced line narrowing and saturation broadening effects in OPFIRL

The variation of the laser linewidth within an optically pumped NH3 FIR laser has been studied theoretically on the basis of three-level quantum system approach. It has been shown that the activated medium within the sample tube of an optically pumped ASE FIR laser can be divided into three regions: A). Laser induced line narrowing region, in which the FIR laser linewidth is less than Lorentz linewidth; B). Saturation broadening region, in which the power density of the FIR. signal becomes large enough to make saturation effect important and the linewidth broadens; C), Self-absorption narrowing region, in which the pumping energy density is below the threshold, so self-absorption dominates and the linewidth decreases. The necessary linewidth of the OPFIRL can be obtained by appropriate selection of the length of the sample tube.     

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.     

Experimental study on miniature pulsed CH3OH far-infrared laser

Using a grating tuned TEA-CO₂ laser with 9P(16) line to pump a 10cm or 20cm long miniature Fabry-Perot cavity CH₃OH laser, pulsed far infrared(FIR) lines of 570.6um and 918um wavelengths were observed, the latter is a new line. Operation performance and spectral characteristics of the miniature CH₃OH laser were studied. The project was supported by the Special Research Foundation of Doctorate Station in University of P.R.C.     

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 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.     

芯片原子钟相干布居囚禁谱线特性研究

通过微型原子蒸汽室产生质量满足要求的相干布居囚禁(CPT)信号是实现芯片原子钟的关键之一.本实验通过对光源实施频率调制和对光场与⁸⁷Rb原子作用产生的信号作相敏解调获得高信噪比的CPT微分谱线, 利用CPT微分谱线研究了CPT信号随工作参数变化的规律以及信号质量对原子钟频率稳定度的影响, 所获研究结果与理论模型预期相符合, 实验结果为芯片原子钟推荐了最佳工作参数.实验所采用的方法利用芯片原子钟自身的资源就可以实施, 因此为芯片原子钟开展性能研究和实施工作参数优化提供了实用的手段.     

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.     

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.     

内泵浦的小型管状Nd：YAG激光器的初步实验研究

介绍了小型化的内泵浦管状Ｎｄ：ＹＡＧ激光器的设计及初步实验结果，斜效率达２．７３％，得到了近３Ｊ的脉冲能量输出。     

Theoretical Study of Optimum Operation of Two-Longitudinal-Mode Optically Pumped Miniature FIR Laser

Based on the semi-classical density matrix equation, the optimum operation of two-longitudinal-mode optically pumped miniature FIR laser was studied theoretically. The relations and the contributions to FIR laser output power of the laser structural parameters and operating parameters were calculated and discussed.     

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.