Super-broadband mid-IR laser systems are under development in the Gas Lasers Lab of the Lebedev Physical Institute. These systems consist of different sorts of molecular gas lasers and various nonlinear crystals converting multi-line emission of those lasers into broadband radiation on sum and difference frequencies. As frequency converters, both main mid-IR nonlinear crystals such as ZnGeP<sub>2</sub>, GaSe, AgGaSe<sub>2</sub> and new ones such as BaGa<sub>2</sub>GeSe<sub>6</sub>, PbIn<sub>6</sub>Te<sub>10</sub> are applied. As radiation sources, repetitively-pulsed Q-switched lasers pumped by both longitudinal DC discharge and transverse slab RF discharge emitting microsecond pulses, and also actively mode-locked e-beam sustained discharge lasers emitting nanosecond pulses are applied. It was experimentally demonstrated for the developed laser systems to emit broadband radiation on hundreds spectral lines covering mid-IR range from ~1.7 to ~17 micron due to sum and difference frequency generation including third harmonic generation.
The results of experimental and theoretical study of the Zeeman splitting of the vibrational-rotational lines in the NO molecule as a function of magnetic field are presented. To record the spectrum the method of laser magnetic resonance (LMR) with using continuous wave frequency-tunable CO laser has been applied. To analyze experimental data of Zeeman splitting, the calculation procedure was developed. This procedure is based on the numerical diagonalization the matrix of the effective molecular Hamiltonian, which includes Zeeman operator corresponding to interaction an external magnetic field with a molecule.
Laser system emitting within IR wavelength range from 2.5 to 16.57 micron is discussed. The hybrid laser system
consists of molecular gas lasers with a frequency conversion in a nonlinear crystal. One gas laser is a carbon monoxide
laser operating in multi-line or single-line mode. Another one is a carbon dioxide laser operating in multi-line mode.
These lasers operate in a Q-switched mode. The laser emission is mixed in various nonlinear crystals producing sum and
difference frequency conversion into above mentioned broadband IR spectral range.
A Master Oscillator - Power Amplifier (MOPA) carbon monoxide laser system emitting nanosecond pulses was
developed on the basis of the wide-aperture pulsed electron-beam-sustained-discharge CO-laser facility. Amplification
parameters including gain and saturation intensity of amplifying media consisted of gas mixtures CO : He or CO : Ar
were measured. The MOPA system emitted a train of nanosecond pulses with peak power up to ~0.1MW on a single
spectral line and up to ~0.4MW with multiline spectrum.
Experimental and modeling results on CO laser frequency conversion are presented. A Q-switched multiline CO laser
with pulse repetition rate 20-150 Hz of sub-microsecond pulses and electron beam sustained discharge frequency-tunable
mode-locked CO laser were used in the experiments on second harmonic generation (SHG) in high-quality ZnGeP<sub>2</sub> and
GaSe crystals. Internal SHG efficiency exceeded 12.4 % in 12 mm ZnGeP<sub>2</sub> crystal. The SHG in 4 mm GaSe crystal was
observed with internal efficiency of 0.3%. A possibility of difference frequency generation of fundamental and firstovertone
CO laser lines to cover spectral range of ~4.0-5.0 μm is discussed. It is estimated that the difference frequency
generation of neighboring lines of both fundamental and first-overtone bands allows one to obtain oscillation in THz
spectral range within ~200-3000 μm.