Several second order nonlinear crystals were numerically studied from a point of view of broadband ultrashort mid-IR pulse generation. The following crystals were considered: AgGaS2, AgGaSe2, ...BaGa2GeSe6, CdGePAs2, CdSiP2, GaSe, HgGa2S4, PbIn6Te10, and ZnGeP2. Crystal properties responsible for efficient frequency conversion were estimated. The optimal pump laser wavelength, mid-IR pulse bandwidth, and relative efficiency were determined and compared for each crystal.
•second order nonlinear crystals.•AgGaS2, AgGaSe2, BaGa2GeSe6, CdGePAs2, CdSiP2, GaSe, HgGa2S4, PbIn6Te10, ZnGeP2.•Ultrashort mid-IR pulse generation.•Broadband frequency conversion.
In this work, we experimentally study intracavity frequency conversion of CO laser radiation in a nonlinear ZnGeP
2
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 BaGa
2
GeSe
6
crystal (11.5%) at the same laser facility.
•Intracavity sum-frequency generation in a slab RF discharge CO laser with a ZnGeP2 nonlinear crystal.•A compact slab RF discharge CO laser simultaneously operating within two wavelength ...ranges.•Spectrum shifting by temperature phase-matching tuning of an intracavity ZnGeP2 nonlinear crystal.
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 ∼ 2.6–2.9 and ∼ 4.9–6.0 μm. The SFG conversion efficiency was up to 2.9 ± 0.1%. The crystal heating from the room temperature up to 115 °C resulted in the SFG spectrum shifting towards the short-wavelength range and in the spectrum width and the number of SFG lines decrease.
We report an experimental study of broadband sum-frequency generation of a nonselective
Q
-switched CO laser (pulse duration, ~0.3 μs; repetition rate, ~90 Hz) in ZnGeP
2
crystals with and without an ...antireflective interference coating. The uncoated crystal surface is found to be optically damaged at a laser radiation intensity of 0.033 GW/cm
2
. Under the same conditions, no damage to the antireflection-coated surface of the crystal is observed. The maximum efficiency of broadband sum-frequency generation of the CO laser in the antireflection-coated sample is 4.8% and turns out to be two times higher than in the uncoated sample. The spectral characteristics of the radiation at sum frequencies do not change in using antireflection-coated and uncoated samples.
Broadband sum-frequency conversion of multiline (~ 60 spectral lines within ~ 5–6 μm wavelength interval) Q-switched CO laser emission in an AR-coated ZnGeP
2
crystal was experimentally studied by ...application of both single-pass and double-pass optical schemes. The maximum conversion efficiency in the double-pass scheme reached ~ 10% that is 2.5 times higher than one obtained in the same optical scheme with an uncoated ZnGeP
2
. The spectrum control of frequency converted radiation by changing angles of incident and reversed CO laser beams in the ZnGeP
2
crystal was implemented within the wavelength range from 2.52 μm up to 2.92 μm. The maximum spectrum width of 0.35 μm was obtained with the double-pass scheme when the angle of the laser beam incident on the crystal and the angle of the deflected reversed laser beam were −4.0° and 1.0°, respectively, the spectral bandwidth being three times broader than one obtained with the single-pass scheme.
•Slab RF discharge Q-switched multiline CO laser with intracavity frequency conversion.•BGGSe crystal operating both intracavity frequency converter and output coupler.•Optimized mode of slab RF ...discharge Q-switched multiline CO laser.•Second and third harmonic generation of CO laser.
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 μm 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.
Abstract
The article analyzes the registered forest fires on the territory of the Republic of Bashkortostan in the period from 2018 to 2020. It is established that during the period under review ...there was an increase in the number and area of forest fires. The causes of most fires were natural (thunderstorms) and human factors.
A terahertz NH
3
laser optically pumped by “long” (~100 μs) pulses of an electron-beam-sustained-discharge CO
2
laser is demonstrated for the first time. The NH
3
laser pulses and the “long” pulses ...of the CO
2
laser are simultaneously measured with nanosecond resolution. The duration and the delay of the NH
3
laser pulse relative to the pump pulse are measured depending on the pulse energy of the pump CO
2
laser. The following emission wavelengths of the terahertz NH
3
laser were observed upon pumping by the 9R(30) line of the CO
2
laser: 67.2, 83.8, and 88.9 μm.
Broadband three-stage frequency conversion of multiline CO laser radiation in a single sample of ZnGeP2 crystal was numerically studied at various crystal temperatures. Decrease of the ZnGeP2 crystal ...temperature resulted in enhancement of efficiency for each frequency conversion stage due to phase-matching shifting. The third stage efficiency at liquid-nitrogen crystal temperature was 1.7-fold higher as compared to one at the room temperature. Also, the crystal temperature decrease resulted in spectral broadening of frequency converted radiation.
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