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

Multispectral anti-reflection coatings based on YbF3/ZnS materials on ZnGeP2 substrate by the IBS method for Mid-IR laser applications

A multispectral anti-reflective coating of high radiation strength for laser applications in the IR spectrum for nonlinear ZnGeP2 crystals has been developed for the first time. The coating was constructed using YbF3/ZnS. The developed coating was obtained by a novel approach using ion-beam deposition of these materials on a ZnGeP2 substrate. It has a high LIDT of more than 2 J/cm2. Optimal layer deposition regimes were found for high film density and low absorption, and good adhesion of the coating to the substrate was achieved. At the same time, there was no dissociation of the double compound under high-energy ions

Verification of an integral figure of merit for mid-IR nonlinear crystals

The examination and verification of a simple integral figure of merit for nonlinear crystals, taking into account different crystal properties, was studied. The examination was carried out on the basis of experimental data on the broadband sum frequency generation of CO laser radiation in ZnGeP 2 , BaGa 2 GeSe 6 , AgGaSe 2 , GaSe, and PbIn 6 Te 10 mid-IR nonlinear crystals. Taking into account spectral and angular phase-matching bandwidths, the figure of merit provides the best agreement with the experiment and can be applied for qualitative, and even quantitative, comparison of the nonlinear crystals

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 2.4–6.2 μm 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 2.2 μm

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

Frequency conversion of mode-locked and Q-switched CO laser radiation with efficiency up to 37%

Frequency conversion of CO laser radiation was experimentally studied in ZnGeP2 and GaSe nonlinear crystals. T

Frequency conversion of mode-locked and Q-switched CO laser radiation with efficiency up to 37%

Frequency conversion of CO laser radiation was experimentally studied in ZnGeP2 and GaSe nonlinear crystals. T

Temperature phase-matching tuning of nonlinear ZnGeP2 crystal for frequency conversion under noncritical spectral phase-matching

Temperature dependences of nonlinear ZnGeP2 crystal indices within the wavelength range of 5.0–6.2 μm (around noncritical spectral phase-matching) were examined with a frequency-selective Q-switched CO laser. The correct dependences were found and applied for numerical study of the spectrum tuning by the crystal temperature changing under the broadband CO laser sum frequency generation. The latter was experimentally studied for the crystal temperature range from the room one up to 145 °C. Requirements for ZnGeP2 crystal temperature changing needed for broadband frequency conversion of 5–7.5 μm radiation were formulated

Optical properties and terahertz radiation generation in a Li2B4O7 crystal

Spectral dependences of components of the refractive index and absorption coefficient in a Li2B4O7 (LB4) nonlinear crystal are determined in the THz range for the first time. Measurements have been carried out in the 0.15–1.6 THz (180–2000 m) spectral range. The measured refractive index components are approximated by the Sellmeier dispersion equations subsequently used to determine the possible interaction types and to calculate the phase-matching angles for THz wave generation at the difference frequency between a Nd:YAG laser and a tunable laser source with a close wavelength. The efficiency of the process is estimated