Infrared and far-infrared laser emissions from a TE CO2 laser pumped NH3 gas

In this paper, infrared (IR) and far-infrared (FIR) laser emissions from a TE CO₂ laser pumped NH₃ gas are reported. 8 IR laser emissions near the wavelength of 12 μm were observed by using 4 different CO₂ laser lines for the pumping. 3 IR laser emissions in P-branch of vibrational-rotational band (ν₂ → G) oscillated simultaneously in two pumping cases, i.e. pumping with the R(30) or R(16) line of 9.4 μm band from the CO₂ laser. 26 FIR laser emissions (26.45 μm ～ 281.0 μm) were observed by using 12 different CO₂ laser lines, and the 10 FIR emissions of them may be new laser emissions as far as we know.     

Simulation of pumping beams self focusing and defocusing in NH3 Raman laser

High power IR pumping beams self focusing and defocusing in NH₃ Raman laser is investigated by numerical methods on the basis of the solution of nonlinear quasioptical equations. The analysis of self focusing have been done for a wide range of parameters of radiation and of active medium. Spatial evolution of the beam configuration have been investigated for different regimes of nonlinear diffraction. Developed model enables to allow exactly for the spectroscopic features of active molecules and may be applied to the analysis of the properties of powerful optically pumped FIR lasers.     

Partly tunable mid-infrared NH3 laser

Using a continously tunable pulsed 20-atmosphere CO₂ laser as a pump source, we generated pulses of mid-infrared radiation, partly tunable in frequency intervals in the range between 200 and 900 cm^–1 via stimulated Raman scattering in gaseous ammonia. As a Raman cell we used a multiple pass cell. We observed for¹⁴NH₃ and¹⁵NH₃ laser lines at 52 different frequencies with 39 lines observed for the first time. Tuning ranges up to 150 GHz and peak powers of several MW were achieved. The quantum efficiency reached 40 %.     

High energy density NH3 laser using an unstable resonator CO2 laser pump

The design and operation of a novel optically pumped molecular gas laser cell, which uses geometrical coupling and is compatible with high energy unstable resonator CO₂ laser pump beams, is described. The attainment of high energy output densities (>0.5J$\text{e}$?1>^-1) from the 12.08 μm and 12.81 μm NH₃ laser transitions using this pumping arrangement is reported.     

Optically pumped NH3 laser using a continuously tunable CO2 laser

The use of a continuously tunable CO₂ laser to optically pump the NH₃ laser via previously inaccessible absorption lines is described. Efficient laser action has thus been achieved in the 11–13 μm region on transitions formerly only obtained in buffered mixtures.     

Self focussing of CO2 laser radiation in NH3 gas

Self focussing of CO₂ laser radiation in ammonia gas is reported for a number of laser emissions in near coincidence with NH₃ absorption lines. Detailed results for the aR(11) NH₃ transition are in excellent accord with theory accounting for intensity dependent saturation of both absorption and the associated anomalous dispersion responsible for nonlinear refraction n₂, giving a value for n₂ of 2.375 x 10^-11 esu torr^-1.     

Compact Raman CH3F, NH3 optically pumped FIR laser

Conclusion The compact superradiant FIR laser is developed using Herriott cell with long optical path as a FIR cell. The employment of the multipass cell gave an opportunity to increase the IR to FIR conversion efficiency in comparison with traditionally constructed FIR lasers and to observe many intensive FIR lines. The given of multipass cell can be useful for employment in continuously tunable FIR lasers.     

Study of miniature optically pumped NH3 fir cavity laser

A miniature NH₃ molecule FIR cavity laser of 15cm in length pumped by a TEA CO₂ laser was built. The spectral characteristics of the cavity laser and the optimum operating parameters were studied.Supported by the National Natural Sciences Foundation of China     

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.     

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 m.     

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     

Classical theory of the dielectric loss for NH3 and ND3

A formula for the frequency dependent dielectric loss in dilute gases of NH₃ and ND₃ describing the deviation of the nonresonant spectrum from the Debye shape and demonstrating the importance of dipole reorientation memory loss effects in lineshift calculations has been developed.     

Pump polarization effect in a superradiant NH3 and CH3F FIR Raman laser

The pump polarization has an evident effect on a superradiant FIR Raman laser both in NH₃ and CH₃F gases when the pump detuning from the resonant line is larger than the Raby frequency. In particular for R resonant lines the circular polarization shows a spontaneous gain about 1.5 times greater than the linear polarization as expected from the theory.     

A high-power far-infrared NH3 laser pumped in a three-mirror CO2 laser cavity with optically-switched cavity-dumping

Results are reported of cavity-dumping a submillimeter radiation high-Q, zig-zag optically-pumped resonator which utilizes a silicon optical switch photo-excited by a NdYAG laser. Peak powers at 152 m approaching 10 kW in temporally smooth pulses of 5 ns (FWHM) duration have been obtained at a pulse repetition rate of 12 Hz. The far-infrared laser radiation, as measured with a scanning metal-mesh Fabry-Perot interferometer and averaged over many pulses, is, upon deconvolution of the 125 MHz instrumental linewidth, found to oscillate in a predominantly single longitudinal mode of width 250 MHz. Theoretical investigations of the transient far-infrared reflectivity of the silicon optical switch predict a rise in the Brewster-angle reflectivity from 0% to nearly 80% in 1 ns, when activated by a Q-switched, frequency-doubled NdYAG laser providing an incident energy density of 50 mJ/cm² in a pulsewidth of 10 ns.     

Compact, high power FIR NH3 laser pumped in a three mirror CO2 laser cavity

A compact CO₂–NH₃ FIR laser system where an NH₃ laser cavity was inserted in pump, three mirror CO₂ laser cavity was designed. The total length of this system was about 1.8 m. Output energy of about 1 mJ (10 KW pea power) was obtained at the 152 m and 90 m lines in NH₃. Power conversion efficiency of 1.7 percent was obtained at the 90 m line.     

NMR spectral densities and two dimensional diffusion in TiS2(NH3)1.0 and TaS2(NH3)x

NMR measurements of proton spin-lattice relaxation times T₁ and T_1? in the layered intercalation compounds TiS₂(NH₃)_1.0 and TaS₂(NH₃)_x (x = 0.8, 0.9, 1.0) are reported as functions of frequency and temperature (100 K – 300 K). These observations probe the spectral density of magnetic fluctuations due to motions of the intercalated molecules at frequencies accessible to the T₁ (4–90 MHz) and T_1? (1–100 kHz) measurements. Since the average molecular hopping time (τ) can be changed by varying temperature, different regions of the spectral density can be examined. For T > 200 K, both T^?1₁ and T^?1_1? vary logarithmically with frequency, reflecting the two dimensional character of the molecular diffusion. The temperature dependence of T₁ suggests that a more accurate picture of the short time dynamics is required. No dependence of relaxation rate on vacancy concentration is found.     

Dissociation of NH3 to electronic ground-state fragments by high-intensity CO2 laser radiation

The dissociation of NH₃ into electronic ground-state fragments NH₂(²B₁) + H by high-intensity CO₂ laser radiation has been observed under essentially collision free conditions and as a function of NH₃ pressure, using laser fluorescence excitation for the NH₂ detection. Luminescence from excited NH₂ (²A₁) produced directly by the CO₂ laser has also been observed. The relative yield of NH₂ (²A₁) is estimated to be smaller than that of NH₂ (²B₁) by several orders of magnitude.     

Interaction of multi-raman-processes in miniature optically pumped NH3 fir laser

The principle of Raman gain superposition was introduced to the theory of multi-Raman- processes interaction. Spectral characteristics of Raman lines from miniature NH₃-optically pumped FiR lasers were studied and measured.supported by the National Nature Science Foundation of P.R.C. and the Special Research Foundation of Doctorate Stations of P.R.C.     

(NH4)2SO4，NH4NO3和(NH4)2SO4/NH4NO3混合气溶胶吸湿质量增长因子的快速测量方法

气溶胶颗粒的吸湿性决定了其尺寸、浓度、化学组成以及相态,从而显著影响着全球气候、大气异相化学以及人类健康。运用在线、原位、连续扫描衰减全反射傅里叶变换红外光谱（ATR-FTIR）技术, 结合线性湿度（RH）控制系统,实现了RH连续变化条件下气溶胶FTIR-ATR光谱的快速测量。根据水弯曲振动谱带（~1 640 cm-1）峰面积随RH的变化,得到了(NH₄)₂SO₄,NH₄NO₃和(NH₄)₂SO₄/NH₄NO₃混合气溶胶的质量增长因子（MGFs）、潮解点（DRH）和风化点（ERH）。与气溶胶的E-AIM模型预测值相比较,实验结果表现出良好的一致性,证实该方法是一种测量大气气溶胶MGFs,ERH和DRH的快速测量方法。     

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.