Terahertz (THz) NH3 lasing with optical pumping by electron-beam-sustained discharge "long" (-100 vs) CO2 laser pulses was obtained. The NH3 laser emission pulses and the "long" pulses of the CO2 pump laser were simultaneously measured with nanosecond response time. The NH3 lasing duration and its delay with respect to the pump pulse were measured for various CO2 laser pulse energies. For the CO2 laser pump line 9R(30), three wavelengths of 67.2, 83.8, and 88.9 vm were recorded. For the CO2 laser pump line 9R(16), only a single NH3 laser line with a wavelength of 90.4 vm was detected.

Based on our experimental study of spectral characteristics of an improved compact CO laser system, the prospects of using such a laser system for solving urgent problems of atmospheric sounding were demonstrated. An increase in the number of laser lines due to intracavity generation of the second harmonic and sum-frequencies in a nonlinear zinc germanium phosphide (ZnGeP2) crystal enriches capabilities of the laser. It was shown that such a CO laser system with frequency conversion in ZnGeP2 crystal can be used for detection and measuring concentration of at least 14 minor natural and pollution gases components of the atmosphere. The advantages and disadvantages of various laser operation modes, and the prospects for using its radiation for atmospheric remote sensing in various spectral ranges are discussed.

A new repetitively pulsed cryogenically cooled slab RF discharge CO laser running in both fundamental and firstovertone bands without its active medium forced replacement with average output power three times as much as that of previous models was developed. Compared to our previous installations, the output power was increased due to using gold-coated copper electrodes of - 1.5 times larger surface area. The fundamental band freerunning lasing was obtained within the spectral range of 5.06-5.92 mu m with average output up to - 40 W. Under Q-switching the laser operated in the spectral range of 4.95-7.0 mu m with pulsed peak power up to 4.5 kW. The first-overtone band lasing was observed in the spectral range of 2.6-3.05 mu m with maximum average power of - 6 W.

In this work, we experimentally study intracavity frequency conversion of CO laser radiation in a nonlinear ZnGeP2 crystal under noncritical phase matching. Various configurations of a laser cavity are considered, in one of which the nonlinear crystal itself was an output mirror. The spectrum of the converted radiation was shifted into the short-wavelength region owing to the temperature tuning of the phase matching in the nonlinear crystal. The maximum average lasing power was obtained at room temperature of the crystal and an output mirror with a transmission T ~ 10% for the fundamental band and reached ~7.0 mW. The power ratio of sum frequency generation and the CO laser radiation was ~16%, which turned out to be higher than the value obtained earlier with the BaGa2GeSe6 crystal (11.5%) at the same laser facility.

A terahertz NH3 laser optically pumped by “long” (~100 μs) pulses of an electron-beam-sustained-discharge CO2 laser is demonstrated for the first time. The NH3 laser pulses and the “long” pulses of the CO2 laser are simultaneously measured with nanosecond resolution. The duration and the delay of the NH3 laser pulse relative to the pump pulse are measured depending on the pulse energy of the pump CO2 laser. The following emission wavelengths of the terahertz NH3 laser were observed upon pumping by the 9R(30) line of the CO2 laser: 67.2, 83.8, and 88.9 μm.

Temperature phase-matching tuning in a ZnGeP2 nonlinear crystal under intracavity CO laser sum-frequency generation (SFG) was for the first time carried out. This slab RF discharge CO laser with the intracavity frequency conversion simultaneously operated within two wavelength ranges of similar to 2.6-2.9 and similar to 4.9-6.0 mu m. The SFG conversion efficiency was up to 2.9 +/- 0.1 %. The crystal heating from the room temperature up to 115 degrees C resulted in the SFG spectrum shifting towards the short-wavelength range and in the spectrum width and the number of SFG lines decrease.

A review of researches that both initiated and provided development of a hybrid IR laser system based on conversion of Q-switched radio-frequency discharge slab CO and CO2 lasers in various nonlinear crystals is presented. The broadband laser system developed operates in the spectral range from ~2 to ~20 μm due to generation of emission on difference and sum frequencies in these crystals.

A waveform of pulsed THz NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> lasing was measured under optical pumping by "long" pulse e-beam sustained discharge (EBSD) CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> laser on 9R (30) and 9R (16) ro-vibrational transitions.

Mode-locking with an acousto-optic modulator was for the first time demonstrated for a repetitively pulsed (150 Hz) slab RF discharge CO2 laser. The mode-locked CO2 laser emitted trains of 5.5 ns pulses following with 27.25 MHz repetition rate. Mode-locking also affected the laser pulses envelope in respect to free-runing mode. The numerical estimation of the laser system scalability indicated an opportunity to develop a very compact CO2 laser emitting sub-nanosecond pulses.

A waveform of pulsed THz NH3 lasing was measured under optical pumping by "long" pulse e-beam sustained discharge (EBSD) CO2 laser on 9R (30) and 9R (16) ro-vibrational transitions.

Q-switched slab RF-discharge multiline CO laser with broadband frequency conversion in BaGa2GeSe6 and ZnGeP2 crystals was developed. The laser system operated within 2.5-6 μm wavelengths and it was tested for absorption measurement of atmosphere gases.

Nonlinear frequency conversion of broadband mid-IR radiation of different molecular gas lasers by various nonlinear crystals converting their multi-line emission into broadband radiation on sum and difference frequencies within ~ 1.7 - 17 micron is discussed.

Analysis of experimental data obtained in study of cryogenic CO laser with glow discharge and cryogenic slab CO laser with RF discharge showed that oxygen concentration in laser mixture is much less than in initial gas mixture. With low oxygen content, ozone plays role of supplier of electrons in cryogenic discharge. Since ionization potential of ozone is somewhat higher than that of oxygen, and ozone quickly condenses on cold walls of cryogenic discharge, conversion of O-2 to O-3 is accelerated. In addition, in plasma-chemical reactions, ozone regenerates carbon monoxide after dissociation. Acceleration of ozone generation in cryogenic barrier discharge was experimentally demonstrated.

Difference frequency generation under mixing of repetitively-pulsed CO- and CO2-laser radiation in AgGaSe2, BaGa2GeSe6 and PbIn6Te10 nonlinear crystals was studied. Efficiency and refractive indices were examined for this frequency conversion into the long-wave domain of ∼12-20 µm in the mid-IR. The highest frequency conversion efficiency of 10-4 was obtained for a relatively new PbIn6Te10 crystal, which is an order of magnitude higher than previous results.

Different frequency conversion processes in the mid-IR were experimentally studied with slab RF discharge CO and CO2 lasers and various nonlinear crystals ZnGeP2, GaSe, BaGa2GeSe6, AgGaSe2 and PbIn6Te10 : second and third harmonic generation of CO laser; sum and difference frequency generation of CO and CO2 lasers. Mid-IR emission on hundreds of narrow spectral lines from 1.7 mu m to 19.3 mu m was obtained

Broadband sum frequency conversion of a slab RF discharge Q-switched CO laser system was performed with two BaGa2GeSe6 crystals resulting in its spectrum lying within 1.7-6.0 um spectral range. The first BaGa2GeSe6 crystal was located in the CO laser cavity and operated as both CO laser sum frequency (second harmonic) generator and laser output coupler. Another BaGa2GeSe6 crystal was applied for external third harmonic generation, i.e. as sum frequency generator for fundamental CO laser radiation and its sum frequencies obtained within the cavity. Peak powers of fundamental CO laser radiation, its second and third harmonics were up to 4.7 kW, 100 W and 0.5 W, respectively.