Jiayin Qin

Study on spectral characteristics and operating parameters of optically pumped NH/sub 3/ FIR cavity laser

By solving the density matrix equations of a quantum system and taking into account the multibeam interference characteristics of a Fabry-Perot cavity, the output power density of an optically pumped NH/sub 3/ far-infrared (FIR) cavity laser was calculated by means of the iteration method. Based on the calculations, the spectral characteristics and operating parameters of the laser were studied. Experimentally, by using inductive metallic meshes as reflectors and couplers, a series of FIR cavity lasers with a sample tube of 10, 20, and 100 cm in length were designed and constructed, and the emissions of the NH/sub 3/ cavity lasers pumped by a TEA-CO/sub 2/ laser with a 10R(8) or 9R(16) line were measured. The experimental results were in good agreement with theoretical calculations.

Monte Carlo Simulation of THz-Pulse Generation from Bulk GaAs Surface

An ensemble Monte Carlo simulation method has been used to study THz-pulse generation from semiconductor GaAs surface excited by a femtosecond laser pulse and biased in high electrical field near 100kV/cm. Electron transport is simulated using the three-valley conduction band model and taking into account acoustic, optical (polar and nonpolar) and intervalley phonon scattering mechanisms. Our simulations show that the THz temporal waveforms have a close relationship with the biased external field and the THz radiation is saturated with the increase of the biased field, these findings have not been exploited by the existing theoretical analyses. Power spectra show that the higher biased electrical field benefits the frequency extension for the THz radiation.

Spikes in Raman spectrum of miniature optically pumped NH3 FIR laser

In this paper, the semiclassical density matrix equation was solved to calculate the spectral characteristics of V2:a--sR(0,0) transition in a miniature optically pumped NH3 far infrared laser (mini-NH3-OPFIRL), which was pumped by CO2-10R(6) line. The results of theoretical calculation showed that the spikes in Raman spectrum of V2:a--sR(0,0) would appear when the operating NH3 gas pressure was higher than a certain critical value or pumping power density was lower than a certain critical value, which was caused by Raman processes interaction of AC-Stark splitting. In our experiment, 298 µm FIR spetral line of a--sR(0,0) pumped by a TEA-CO2 laser with 10R(6) line was observed but the spikes could not be observed owing to the limitation of the resolution of the F-P interferometer.

Operating parameter optimization of optically pumped CH3OH far-infrared laser

By solving the density matrix equations of a quantum system, the output power intensity of an optically pumped CH3OH FIR laser (CH3OH-OPFIRL) was calculated by means of iteration method, and the spectral characteristics were got. Base on the calculation, optimization of operating parameters including operating gas pressure, pumped power and output coupling coefficient of the CH3OH cavity laser were systematically studied. Experimental, a series of FIR emissions of the CH3OH cavity laser pumped by TEA-CO2 laser with 9P(16) line were measured. The experimental results were in good agreement with theoretical calculations.

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.

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.

Spectral Characteristics of Miniature Two-Longitudinal-Mode Optically Pumped FIR Laser

With the assumption that the pump source was two-longitudinal-mode, the semiclassical density matrix equation of a three-energy-level system was solved. By means of iteration method, the spectral characteristics of miniature two-longitudinal-mode optically pumped NH3 far-infrared cavity laser, which was pumped by CO2-9R(16) line, were calculated numerically. The influences of operating parameters on laser spectrum were studied intensively.

The tuning characteristics of optically pumped fir cavity laser

Based on the quantum mechanics theory of density matrix and the principle of multiple-beam interference, the tuning characteristics of optically pumped NH3 FIR lasers were studied. A series of metallic mesh Fabry-Perot cavity lasers with sample tubes of 10cm, 20cm and 100cm in length were constructed and operated successfully, and the FIR laser spectra of the NH3 cavity lasers pumped by a TEA-CO2 laser were measured.

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.

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.