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.     

CW and pulsed Pb1–xSnxSe diode laser spectroscopy of 14NH3 and 15NH3 molecules

The absorption spectra of ¹⁴NH₃ and ¹⁵NH₃ molecules from 930 cm^-1 to 1220 cm^-1 have been obtained with CW and pulsed Pb_1–xSn_xSe diode lasers. The laser emission frequency has been tuned by varying crystal composition, diode temperature, hydrostatic pressure, or injection current. The registration of the absorption spectra with CW PbSe laser continuously tuned by varying hydrostatic pressure has been accomplished. The possibility of gas isotope abundancies measurements by diode lasers is considered.     

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     

Optimized operation of optically pumped NH3 laser emission at 12.08 μm and 12.81 μm

Based on the semi-classical density matrix equations, optimized operation of optically pumped NH₃ MIR laser emission at 12.08μm and 12.81μm was studied theoretically and experimentally. The effect of pump power, gas pressure and buffer gas N₂ on MIR output power were discussed in detail. Supported by theNatural Science Foundation of Guangdong Province, P.R. China.     

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.     

Absorption measurements using CW MIR NH3 laser

The intensity and half-widths of the v₂ [sP(7,0)] line of ammonia have been measured using an optically pumped CW NH₃ laser. The influence of buffer gas is reported.     

Modeling of high-pressure 12-μm NH3 lasers

Experimental measurements of small-signal gain in an optically-pumped NH₃ amplifier are carried out at pressures ranging from 40 Torr to 760 Torr, and the results are used to validate a rate-equation model describing the amplifier dynamics. The gain measurements show that dilute mixtures of <0.5% NH₃ in N₂ are reqired to minimize the problems of gas heating due to pump absorption. The model is used to extrapolate the results to gas pressures of several atmospheres, and to demonstrate the potential for highpressure operation of optically-pumped NH₃ lasers. For a pump intensity of 100 MW/cm², calculations indicate that operation of an NH₃–N₂ laser is feasible up to a pressure of 10 atm, which would provide a maximum continuous tuning range of 4 cm^–1. High-resolution spectroscopy reveals that gain on a few NH₃ transitions is eliminated at high pressures due to the presence of overlapping absorptions in other NH₃ bands.     

Pulsed laser deposition of fluoride glass thin films

The development of integrated waveguide lasers for different applications such as marking, illumination or medical technology has become highly desirable. Diode pumped planar waveguide lasers emitting in the green visible spectral range, e.g. thin films from praseodymium doped fluorozirconate glass matrix (called ZBLAN, owing to the main components ZrF₄, BaF₂, LaF₃, AlF₃ and NaF) as the active material pumped by a blue laser diode, have aroused great interest. In this work we have investigated the deposition of Pr:ZBLAN thin films using pulsed laser radiation of λ = 193 and λ = 248 nm. The deposition has been carried out on MgF₂ single crystal substrates in a vacuum chamber by varying both processing gas pressure and energy fluence. The existence of an absorption line at 210 nm in Pr:ZBLAN leads to absorption and radiative relaxation of the absorbed laser energy of λ = 193 nm preventing the evaporation of target material. The deposited thin films consist of solidified and molten droplets and irregular particulates only. Furthermore, X-ray radiation has been applied to fluoride glass targets to enhance the absorption in the UV spectral region and to investigate the deposition of X-ray treated targets applying laser radiation of λ = 248 nm. It has been shown that induced F-centres near the target surface are not thermally stable and can be easily ablated. Therefore, λ = 248 nm is not suitable for evaporation of Pr:ZBLAN.     

Effects of Buffer Gas N2 on Miniature Optically Pumped NH3 Submillimeter Wave Cavity Laser Emission at 67.2 μm

The effect of buffer gas N₂ on miniature optically pumped NH₃ submillimeter wave (SMMW) cavity laser emission at 67.2m was studied theoretically and experimentally. It has been found that: 1. N₂ had a positive effect on laser output of 67.2m, 2. sharp absorption in laser spectrum under certain gases mixture pressure corresponded to the threshold of 'bottleneck effect.     

Multi-Raman Effect and Longitudinal-Mode Structure in Optically Pumped Submillimeter Wave Laser

Based on semi-classical density matrix theory, multi-Raman interaction in multi-longitudinal-mode CO₂-9R (30) optically pumped NH₃ molecules laser was studied theoretically. With different parameters such as pumping power and operating gas pressure, the effect of multi-Raman interaction and the longitudinal-mode structure of submillimeter wave laser were also discussed.     

Multiwatt optically pumped ammonia laser operation in the 12–13 μm

Design and operating caracteristics of high pulse repetition rate NH₃ laser producing up to 20 W of average output power are described. The NH₃ laser, operating in the 12–13 μm region was optically pumped with a high pulse repetition rate TEA CO₂ laser. Dependences of the NH₃ laser output on the pump energy, ammonia and buffer gas pressures and pulse repetition rate have been studied. The conversion efficiency of up to 16% has been received.     

Effects of Buffer Gas on the Output of Optically Pumped NH3 Far-Infrared Cavity Laser

By solving the semi-classical density matrix equations and developing a buffer gas mechanism model, the effects of buffer gas on the output power of optically pumped NH₃ far-infrared cavity laser were calculated and verified by experiment. Our results showed that: the output power of NH₃ far-infrared laser could be increased when certain buffer gas was added into the laser medium, and there existed an optimum ratio of gases mixture and an optimum operating gas pressure which could make the output power of far-infrared laser reach maximum.     

703-to 731-nm FI laser excited by a transverse inductive discharge

It is proposed to use a pulsed transverse inductive discharge for exciting gas lasers operating on electron transitions in atoms and molecules. An electron transition laser on fluorine (FI) atoms pumped by a transverse inductive discharge is developed. Lasing at three wavelengths (703.75, 712.79, and 731.1 nm) is obtained by exciting He-F₂ (NF₃) gas mixtures in a pressure range from 20 to 350 Torr. The results of experimental investigation of the spectral, temporal, and energy characteristics of the inductive FI laser are presented.     

An efficient cavity for optically pumped terahertz lasers

The efficiency of a simply designed cavity for optically pumped pulsed terahertz lasers is studied experimentally. A coated Ge and a crystal quartz act as the input and output windows, respectively. The thickness of the Ge window is designed according to etalon effects to maximize terahertz reflectivity. NH₃ is filled in the cavity as the active medium. When NH₃ is pumped by the 10P(32) line of a TEA CO₂ laser, intense 151.5 μm terahertz radiation is emitted. As high as 19.6 mJ terahertz radiation is extracted from 1.57 J pump energy. The corresponding photon conversion efficiency reaches 35.3%.     

Superradiance effects on the infrared absorption and vibrational temperature of optically pumped molecules

Using controlled feedback and coincident far infrared absorption, we have shown that the superradiant emission process in NH₃ pumped by the 9R16 line of a CO₂ TEA laser has a marked effect on the absorption of laser energy and vibrational heating of the gas. Since many polyatomic molecules pumped by IR laser are efficient superradiant far infrared sources, the effect is important for laser induced fluorescence studies in these polyatomics.     

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.     

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     

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.     

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.     

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.