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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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 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 m far-infrared laser spectrum were also discussed theoretically.     

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.     

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.     

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.     

激光波长对煤激光诱导击穿光谱特性影响的试验研究

我国电站入炉煤种复杂多变,实时快速获取煤质成分对保障锅炉的安全、高效、低污染运行具有重大意义。将激光诱导击穿光谱(LIBS)技术应用于燃煤煤质测量,观测了不同波长激光(355,532和1 064 nm)诱导产生的等离子体时间演变特性和不同电离特性元素的谱线时间特性,对比了出现屏蔽效应时的能量阈值随激光波长的变化特征,并研究了激光波长对煤LIBS光谱特性的影响规律。结果发现：使用532 nm激光作为激发光源时,煤LIBS光谱具有最强的谱线信号强度,且出现等离子体屏蔽效应的能量阈值也较高,是一种较理想的激发光源,为LIBS技术在煤质测量领域的工业应用提供了实验依据。     

复合阴极缓冲层Alq_3∶CsF对CuPc/C_(60)电池性能的影响

通过Alq_3∶CsF复合阴极缓冲层来优化CuPc/C_(60)有机小分子太阳能电池的性能。当Alq_3∶CsF厚度为5nm,CsF的掺杂比例为4%时,加入复合阴极缓冲层器件较Alq_3阴极缓冲层器件的能量转化效率提高了49%,到达0.76%,并且在室温、大气的条件下,器件的稳定性也得到了保持,与未加阴极缓冲层的器件相比,半衰期提高了6倍,达到9.8h。通过紫外-可见吸收、外量子效率和单载流子传输器件等研究了器件效率改善的主要原因是掺入CsF后,调节界面能级,改善了Alq_3的电子传输特性,提高了器件的短路电流和填充因子。比较分析复合阴极缓冲层器件于空气中放置不同的时间的电流电压曲线,表明Alq_3∶CsF可以保持Alq_3的良好稳定性,可以很好地阻挡氧气与水分的扩散,提高器件的寿命。     

低温缓冲层对氧化锌薄膜质量的影响

利用金属有机化学气相沉积(MOCVD)法,在Si衬底上外延生长ZnO薄膜。为了改善氧化锌薄膜的质量,首先在Si衬底上生长低温ZnO缓冲层,然后再生长高质量的ZnO薄膜。通过XRD、SEM、光致发光(PL)光谱的实验研究,发现低温ZnO缓冲层可有效降低ZnO薄膜和Si衬底之间的晶格失配以及因热膨胀系数不同引起的晶格畸变。利用低温缓冲层生长的ZnO薄膜的(002)面衍射峰的强度要比直接在Si上生长的ZnO薄膜样品的高,并且衍射峰的半高宽也由0.21°减小到0.18°,同时有低温缓冲层的样品室温下的光致发光峰也有了明显的增高。这说明利用低温缓冲层生长的ZnO薄膜的结晶质量和光学性质都得到了明显改善。     

掺铒光纤激光器输出特性的研究

根据掺铒光纤激光器的速率方程,对线性腔连续掺铒光纤激光器的输出特性进行了详细的理论分析,得到了980 nm泵浦的掺铒光纤激光器在稳态条件下的解析表达式.利用数值模拟结果对光纤激光器的上下能级粒子数和泵浦功率沿光纤长度分布以及泵浦阈值、斜率效率等进行了分析和讨论,并进行了980 nm泵浦的掺铒光纤激光器的实验,实验证明:光纤激光器的阈值与理论计算基本一致.     

组织凝固性坏死对基于纵向弛豫时间的磁共振测温的影响

高强度聚焦超声（High Intensity Focused Ultrasound,HIFU）治疗肿瘤时,为了保证治疗的安全性和有效性,需要对组织温度分布进行实时监测.磁共振成像（Magnetic Resonance Imaging,MRI）具有对温度敏感的成像参数,可以无创检测组织温度.本文结合组织相变对测温的影响,探讨了磁共振测温（Magnetic Resonance Thermometry,MRT）技术能否用于实时监控HIFU治疗.利用两态快速交换模型,提出在组织凝固性坏死的相变前后,MRI的纵向弛豫时间（T₁）参数与组织温度之间具有不同关系.并通过实验验证了上述假设.相对于传统的磁共振测温方法模型,本文考虑了HIFU治疗过程中组织相变对检测温度的影响,对利用磁共振测温引导HIFU治疗具有重要的参考价值.     

激光引发自由基反应磁效应的光谱学研究

“动态自旋化学”(dynamic spin chemistry)作为一门新兴的交叉研究领域,其重要性已得到广泛的共识。涉及的研究内容包括： 化学反应的磁效应(MFE)、同位素效应(MIE)、化学诱导动态核极化(CIDNP)和化学诱导动态电子极化(CIDEP)。文章简要介绍了激光引发自由基反应的磁效应发展历史及其光谱学研究方法。分析并总结了自由基反应磁效应产生的原因、单-三转换理论及磁效应机理。同时,也为国内同行介绍了自由基反应磁效应研究新的发展动态。