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Radiation with a wavelength of ~4 µm was used for quasi-collinear excitation of the Fe:ZnSe laser. The highest output energy was achieved at the optimal crystal temperature of 230 K with the generated radiation wavelength of ~4.5 µm.

We demonstrate an experimental and theoretical comparison of non-oxide LiGaS2, HgGa2S4, and AgGaS2 crystals performance for wavelength conversion into the near and mid-IR range 1.5–8 μm in optical parametric amplifier pumped by Cr:Forsterite laser, delivering 100 fs pulses at 1.24 μm. It is shown that exceptionally high total energy conversion efficiency into the idler (4–5 μm) and signal (1.65–1.8 μm) waves up to 18% can be achieved using the HGS crystal, providing high nonlinearity, while the LGS crystal is more preferable for generating few-cycle mid-IR pulses due its unique dispersive properties. Our source features high peak power in gigawatt regime (0.4–2.4 GW) with pulse duration below 80 fs and optical synchronization with high harmonic generation (HHG) and THz beamlines, which is ideal for pump-probe experiments of nonlinear and strong-field physics. [ABSTRACT FROM AUTHOR]

We have measured the polarized Raman scattering and IR reflection spectra of a BaGa2GeS6 crystal, the Ga and Ge atoms of which are disordered, randomly occupying crystallographic positions of the same kind. The IR reflection spectra have been processed by the dispersion analysis method. The dispersion of phonons, the density of phonon states, the electronic band structure, and the partial densities of electronic states have been calculated in the DFT approximation using the alchemical potential method for disordered Ga and Ge atoms. It has been found that the stretching vibrations in the vibrational spectra are separated from the bending modes by a gap of about 100 cm–1 and that the band structure of the crystal has an indirect energy gap. [ABSTRACT FROM AUTHOR]

Nonlinear crystals of PbGa6Te10 and PbIn6Te10, transparent into the mid- and far-infrared spectral range up to beyond 30μm, are grown and some of their linear and nonlinear optical properties are characterized. This information obtained from single crystals is used for the study and construction of binary phase diagrams of the systems PbTe-Ga2Te3 and PbTe-In2Te3. [ABSTRACT FROM AUTHOR]

We report on the development of a tunable (1.5-6.5 µm) femtosecond optical parametric amplifier (OPA) based on a novel, to the best of our knowledge, BaGa 2 GeS 6 (BGGS) crystal with a Cr:Forsterite pumping laser. Total conversion efficiency as high as 28% is achieved in a robust two-stage setup resulting in the generation of a 340-µJ 1.67-µm signal and 100-µJ 4.65-µm idler pulses. A 5-optical-cycles 94-fs 6-µm idler pulses are demonstrated with a propriate dispersion compensation by Ge and GaAs plates. An experimental estimate is given for the effective nonlinearity of a BGGS material, which for our nonlinear process reaches 19.5 pm/V for Type II phase matching. The crystal is additionally tested as a final amplifier in a high-energy OPA, where total output reaches 1.2 mJ with more than 40% conversion efficiency. The demonstrated high nonlinearity, high damage threshold, and chemical stability of the polished surface make BGGS crystal an ideal candidate for the development of high-energy OPAs with multi-millijoule pumping lasers.

Difference frequency generation under mixing of repetitively-pulsed CO- and CO 2 -laser radiation in AgGaSe 2 , BaGa 2 GeSe 6 and PbIn 6 Te 10 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 PbIn 6 Te 10 crystal, which is an order of magnitude higher than previous results.

A compact repetitively pulsed broadband carbon monoxide (CO) laser system with intracavity frequency conversion, for which a nonlinear crystal was also used as an output coupler, was launched for the first time, to the best of our knowledge. The laser system simultaneously operated in two spectral ranges: CO laser fundamental band (4.9-6.0 μm) and its sum frequencies band (2.45-2.95 μm). Different designs of the laser cavity were considered. Peak powers of the fundamental and sum frequencies laser pulses were up to 2 kW and 10 W, respectively.