Raman Effect in Two-Longitudinal-Mode Superradiant Terahertz Laser

Multi-Raman effect in optically NH₃ pumped superradiant two-longitudinal-mode CO₂-9R(30) laser was theoretically studied. And with different pumping power, operating gas pressure and length of laser tube, the rule of multi-Raman interaction and its effect to THz laser spectral characteristics were discussed.     

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.     

Comparison Between Single-Longitudinal-Mode and Two-Longitudinal-Mode Pumping Cavity OPSMMWL

A CO₂ infrared laser system with a etalon to be the longitudinal mode select equipment was set up to be the optically pump source, as well as a mini NH3 with 20cm long sample tube to be the sub-millimeter wave laser. CO2-9R(16) line was chose to pump the mini-NH3 SMMW laser, and 90.4um SMMW line was obtained by single-longtudinal-mode or two-longitudinal-mode pumping. Experimental comparison of output power and operating gas pressure between single and two-longitudinal-mode OPSMMWL were studied. It was found that the two-longitudinal-mode OPSMMWL could get higher output power and broader spectrum, existed a lower operating gas pressure and wider range of operating gas pressure. These experimental results verified the theoretical calculations before.     

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.     

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.     

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. The project was supported by the Special Research Foundation of Doctorate Station in University of P.R.C.     

Pulsed laser action of Pr:GdLiF4 at room temperature

We realized, to our knowledge for the first time, laser emission in Pr:GdLiF₄ at seven wavelengths: 522 nm, 545 nm, 604.5 nm, 607 nm, 639 nm, 697 nm, and 720 nm. The crystal was pumped with an excimer laser pumped dye laser at 468 nm. All laser experiments were carried out at room temperature. We also achieved pulsed room temperature laser oscillation of Pr:KYF₄ at 642.5 nm pumped at 465 nm wavelength.     

Infrared multi-line NH3 laser and its application for pumping an InSb laser

In this paper, infrared (IR) emissions from a TE CO₂ laser pumped NH₃ laser are reported. 38 IR laser lines were obtained from a CO₂ 9R(30) line pumped NH₃ : N₂ mixture by cooling a NH₃ laser tube, and 13 lines of them were new emission lines as far as we known. Four Q-branch lines were included and the others belonged to P-branch transitions. The 12.078 μm line, which was the strongest line in this experiment, was used to pump an InSb spin-fip Raman (SFR) laser which could be tuned from 13.35 to 13.55 μm.     

Stimulated rotational Raman scattering at multiwavelength under tea CO2 laser pumping with a multiple-pass cell

Stimulated rotational Raman scattering (SRRS) at multiwavelength pumped by TEA CO₂ laser was demonstrated in this paper. Raman mediums were cooled by liquid-N₂ and a multiple-pass cell (MPC) with 25 passes was designed and used. When the para-H2 was pumped by single-longitudinal-mode (SLM) circular polarized TEA CO₂ laser on 10P(20), 9P(20), and 10R(20), 50 mJ 16.95 μm, 350 mJ 14.44 μm, and 536 mJ 16.9 μm radiations were obtained, corresponding to energy conversion efficiency of 1.2, 11.7, and 13.4%, respectively. When the ortho-D₂ was pumped by CO₂ laser on 10R(18), 108 mJ 12.57 μm Raman laser was obtained with energy conversion efficiency of 2.9%.     

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.     

Efficient 1.06 μm laser operation in an unprocessed Nd3+:BaGd2(MoO4)4 cleavage microchip

A 1.2 mm thick microchip cleaved from a 1.2 at.% Nd³⁺: BaGd₂(MoO₄)₄ crystal was used as the laser gain medium directly. The laser cavity mirrors were coated on the microchip without cutting and polishing. In the 1.06 μm quasi-CW laser operation, the microchip was pumped by a Ti:sapphire laser with a duty cycle of 10%, the threshold is 10 mW, and the slope efficiency is 50%. In the CW laser operation pumped by a diode laser, the threshold and slope efficiency are 140 mW and 33%, respectively. The results demonstrate that the unprocessed surfaces of the cleaved microchip have good enough flatness and parallelism for laser operation.     

Comparison of eye-safe KTA OPOs pumped by Nd:YVO4 and Nd:YLF lasers

An eye-safe KTA OPO pumped by a Nd:YLF laser is demonstrated and a comparison with that pumped by a Nd:YVO₄ laser is performed. Although the slope efficiency of the continuous-wave free-running Nd:YLF laser is lower than that of the Nd:YVO₄ laser, the performance of KTA OPOs pumped by the Q-switched Nd:YLF laser is better, especially at lower repetition rates. The slope efficiency of KTA OPO pumped by a Nd:YLF laser is 14.6% at 30 kHz and 11.04% at 10 kHz. The better energy storage ability of Nd:YLF makes it an excellent laser medium in IOPOs.     

Identification and prediction of optically pumped laser lines in ozone

Three previously observed optically pumped submillimeter laser lines are shown to be pure rotational transitions in the v₃ = 1 vibrational level of ozone. Using other anticipated coincidences between CO₂ laser lines and ozone absorption lines, a number of optically pumped laser transitions are predicted.     

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.     

Diode-pumped Nd:LuVO<Subscript>4</Subscript>-Nd:YVO<Subscript>4</Subscript> laser at 492 nm with intracavity sum-frequency-mixing in LiB<Subscript>3</Subscript>O<Subscript>6</Subscript>

We present for the first time a Nd:YVO₄ laser emitting at 1064 nm intracavity pumped by a 916 nm diode-pumped Nd:LuVO₄ laser. A 809 nm laser diode is used to pump the Nd:LuVO₄ crystal emitting at 916 nm, a Nd:YVO₄ laser crystal was pumped at 916 nm and lased at 1064 nm. Intracavity sum-frequency mixing at 916 and 1064 nm was then realized in a LiB₃O₆ (LBO) crystal to reach the blue range. We obtained a continuous-wave output power of 216 mW at 492 nm under 19.6 W of incident pump power at 809 nm.     

Interaction of polarized fields with A resonant medium of NH3 laser

A numerical model of optically pumped FIR laser for arbitrary field polarizations is discussed. A restricted set of linear equations is proposed. Calculated spectra for NH₃ laser pumped by CO₂ laser are presented. The validity and limitations of the model are considered.     

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     

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.     

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. Supported by the Natural Sciences Foundation of Guangdong Province, PRC     

Measurements and assignments of new large offset CD3OH FIR laser lines

By using an acoustooptic modulator we extend the 300 MHz tunability of a waveguide CO₂ laser to 480 MHz. The CD₃OH was optically pumped by the 10R(32), 10R(34), and 10R(36) CO₂ laser lines, and 17 new FIR laser lines were discovered. The Stark effect on previously known FIR laser lines was investigated, and some tentative FIR laser lines assignments are suggested.