Multiline CO Laser Research Articles

Broadband sum-frequency conversion of multiline Q-switched CO laser emission under its double-pass through AR-coated ZnGeP2 crystal

Broadband sum-frequency conversion of multiline Q-switched CO laser emission under its double-pass through AR-coated ZnGeP2 crystal

Broadband sum-frequency conversion of multiline Q-switched CO laser emission under its double-pass through uncoated ZnGeP2 crystal

Broadband sum-frequency conversion of multiline Q-switched CO laser emission in a single uncoated ZnGeP2 crystal was experimentally studied by application of single-pass and double-pass optical schemes. The laser emitted sub-microsecond pulses of 4 kW peak power at 100 Hz pulse repetition rate on ∼60 spectral lines within ∼5–6 μm wavelength interval. The sum-frequency emission spectrum consisted of at least ∼100 spectral lines covering the wavelength interval of ∼2.5–2.9 μm. The double-pass scheme provided about 30% higher efficiency as compared to a traditional single-pass one, while the spectral bandwidth of frequency converted radiation was the same. Moreover, a feasibility of slight spectral bandwidth extension by a variation of a reverse beam direction was demonstrated for the double-pass scheme.

Influence of ZnGeP2 crystal temperature on broadband cascaded frequency conversion (numerical study)

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.

Frequency down-conversion of multiline CO laser into the THz range with ZnGeP2 crystal

Frequency down-conversion (difference frequency generation) of a multiline Q-switched CO laser with a ZnGeP2 crystal was numerically studied. Two options of the CO laser spectrum were considered: “narrow” (44 lines) and “broad” (150 lines) ones. An influence of the ZnGeP2 crystal absorption on THz generation was taken into account and was shown to be significant. It affected optimal phase-matching angle, THz spectrum and frequency conversion efficiency, which were optimized by the crystal length. Maximal frequency conversion efficiency of 0.007% was numerically obtained for the “narrow” spectrum due to less influence of the crystal absorption.

CO laser sum-frequency comb for atmosphere sensing

Sum-frequency spectrum of non-selective (multi-line) CO laser radiation generated in ZnGeP2 crystal under noncritical spectral phase-matching conditions was experimentally studied with spectral resolution of ∼0.1 cm−1. The number of spectral lines for this spectrum was found to be about an order of magnitude larger than for previously reported one. Its spectral structure looked like a broadband mid-IR comb of multi-line groups having complicated substructure. That is attractive for the atmosphere sounding by both differential absorption technique and absorption line profile spectroscopy. A list of the atmosphere gases and pollutants that could be detected by these procedures was considered. An opportunity of absorption line profile measuring by means of CO laser sum-frequency comb was experimentally demonstrated for CO2 molecules.

Numerical Study of Multiline CO Laser Frequency Conversion in a ZnGeP2 Crystal to the THz Range

A numerical simulation was performed for frequency conversion of multiline CO laser radiation to the THz range by difference frequency generation in a ZnGeP2 crystal. It was shown that the difference frequencies spectrum can be tuned in the wavelength interval of 70–1300 μm by tuning the phase-matching angle in the range of 11° to 55°. The maximal peak power of difference frequencies radiation (integral over the spectrum) was ~0.23 W at 45° phase-matching angle, which corresponds to a peak power conversion efficiency of 6 × 10−5.

Sum frequency conversion of multiline CO laser emission in BaGa2GeSe6 crystal of one cm long

Sum frequency conversion of multiline Q-switched CO laser radiation was studied in 10.4mm-long BaGa2GeSe6 crystal under noncritical spectral phase-matching conditions. Spectrum of the CO laser consisted of 51 emission lines in the wavelength range of 4.95-6.20 μm. The frequency converted spectrum contained 85 spectral lines in the wavelength range of 2.5-2.8 μm. The internal energy conversion efficiency (taking into account optical losses on uncoated facets of the crystal) was up to 1.7%.

Broadband (1.7–6.0 μm) multiline CO laser system with intra- and extracavity sum frequency generation in BaGa2GeSe6 crystals

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.

Three-stage frequency conversion of sub-microsecond multiline CO laser pulse in a single ZnGeP2 crystal.

Broadband three-stage frequency conversion of multiline sub-microsecond CO laser radiation in a single sample of ZnGeP2 crystal was experimentally and numerically studied for the first time, to the best of our knowledge. As a result, the hybrid laser system emitted more than 200 narrow spectral lines within the 2.4-6.2μm spectral range. The measured conversion efficiencies of the first, second, and third stages were about 4.8%, 0.4%, and 0.05%, respectively. Our numerical simulation demonstrated that the third stage of this frequency conversion can extend the laser system spectrum toward the shorter wavelength of 2.2μm.

Sum-frequency generation of Q-switched CO laser radiation in BaGa2GeSe6 and GaSe nonlinear crystals

Sum-frequency generation of multiline Q-switched CO laser radiation is studied in the BaGa2GeSe6 (BGGSe) crystal and in the GaSe crystal. The maximal external conversion efficiency obtained in the BGGSe crystal is 0.7%, which corresponded to the internal conversion efficiency of 1% taking into account optical losses under reflection from uncoated facets of the crystal. The maximum external conversion efficiency in the GaSe crystal is 0.15% with internal efficiency 0.31%. Effective nonlinearity of BGGSe crystal is determined through the ratio between measured efficiency in BGGSe and GaSe crystals. Effective nonlinearity for sum-frequency generation of the CO laser emission in the BGGSe crystal is deff = 42 ± 14 pm/V, and nonlinear coefficient of this crystal is d11 = 49 ± 15 pm/V.

Spectral characteristics of multi-line Q-switched CO laser radiation frequency converted in ZnGeP2

Lasing on different spectral lines belonging to a giant pulse of multi-line Q-switched CO laser was experimentally studied. The Q-switched CO laser emitted a giant microsecond pulse that consisted of about one hundred subpulses corresponding to different rotational–vibrational transitions. Amplitude, time delay and duration were measured for such a laser subpulse, and processes affecting formation of the CO laser giant pulse spectrum were analyzed. These data were taken into account to correctly estimate peak power and the number of spectral lines of radiation formed under sum frequency conversion of the CO laser radiation in nonlinear ZnGeP2 crystal.

Influence of multi-line CO laser focusing on broadband sum-frequency generation

The influence of a multi-line CO laser focusing on spectral characteristics of broadband sum-frequency generation in ZnGeP2 nonlinear crystal was experimentally and numerically studied. Maximal frequency conversion was experimentally observed under a tight focusing laser beam of a multi-line CO laser rather than a single-line one. The tight focusing resulted in a broadening sum-frequency generation spectrum and an increasing total, i.e. integrated over the spectrum, frequency conversion efficiency. These effects were due to the increasing phase-matching bandwidth and angular dispersion. The maximal conversion efficiency of the multi-line CO laser was numerically demonstrated to take place at a focal length of 0.4 times that required for the single-line one.

Absorption of the CO laser sum frequency radiation obtained in a nonlinear crystal AgGaSe2 by molecular gases

The broadband laser system based on multi-line Q-switched CO laser was experimentally studied in a nonlinear crystal AgGaSe2. The internal efficiency of sum frequency generation reached 1%. Test experiments on measurement of the absorption of the CO-laser sum frequency radiation by such gaseous substances as nitrous oxide and carbon dioxide were realized. A comparison of the experimental data with the theoretically calculated absorption spectrum of radiation was obtained.

Broadband two-stage frequency conversion of CO laser in AgGaSe(2) crystal.

For the first time, to the best of our knowledge, a broadband two-stage frequency conversion of multiline CO laser radiation was theoretically and experimentally demonstrated in a single AgGaSe2 crystal. The first stage is sum frequency generation of CO laser radiation. The second stage is concurrent difference frequency generation within 4.3-4.9 μm spectral range when mixing sum frequency radiation with the pump radiation in the same AgGaSe2 crystal. Internal sum frequency generation efficiency of multiline CO laser was up to 1%, while internal difference frequency generation efficiency was up to 0.065%.

CO激光在非线性晶体ZnGeP2和GaSe中的混频效应

The CO laser frequency mixing in high-quality ZnGeP2 and GaSe crystals is studied to obtain the 2.15-1 500 μm coherent sources.Secondary Harmonic Generation(SHG),sum-and difference frequency generations are considered as a method for the CO laser frequency mixing and the mode-locking as an efficient way to improve the mixing efficiency.Results show that the internal SHG efficiency of Q-switched multiline CO laser radiation has exceeded by 0.3% for GaSe crystal and has reached by 1.1 % for ZnGeP2 crystal.When the SHG is in ZnGeP2,the internal efficiency of electron beam sustained discharge frequency-tunable mode-locking CO laser is up to 12.5 %.Simultaneous SHG and sum frequency generation show the same output spectrum.It is shown by modeling that the sum and difference frequency generations of neighboring lines of both fundamental and first overtone bands can allow one to get the oscillation,respectively,at 4.0-5.0 μm and 100-≥1 200 μm(THz).In conclusions,the frequency mixing of mode-locked CO laser emission lines in ZnGeP2 crystals allows some one to design 2.15-≥1 500 μm coherent sources with the power frequency conversion efficiency up to or over 12.5%.

Carbon monoxide laser emitting nanosecond pulses with 10 MHz repetition rate

Actively mode-locked electron-beam-sustained-discharge CO laser producing a train of ∼5–15 ns (FWHM) spikes following with repetition rate 10 MHz for both single-line and multiline mode of operation in the mid-IR range of ∼5 μm was experimentally studied. Total laser pulse duration was ∼0.5 ms for both mode-locked and free-running laser. Specific output energy in multiline CO laser mode of operation was up to 20 Jl −1 Amagat −1 and the laser efficiency up to 3.5%. The active mode-locking was achieved for single-line CO laser mode of operation in spectral range 5.2–5.3 μm. This sort of radiation can be used for pumping an optical parametric amplifier for optical stochastic cooling in relativistic heavy ion collider, for laser ablation, and for studying vibrational and rotational relaxation of CO and NO molecules.