Adam Říha

Crystals with minimal depolarization effects and losses are desired for specific applications to preserve the orientation of the generated radiation polarization. This work presents an experimental method for measuring the depolarization of radiation propagating through flashlamp pumped Nd:YAG laser rods. Two differently oriented Nd:YAG crystal cuts and with the same concentration of Nd ³⁺ ions and the same dimensions were investigated and compared. A passively Q-switched Nd:YAP/Cr:YAG compact laser system that generates linearly polarized radiation at a wavelength of 1078nm was used as a source of diagnostic pulse radiation. The experimental setup presented enables for the sensitive detection of polarization changes. It can serve as a diagnostic and classifying tool for evaluating the crystal quality after growth and processing.

The temperature dependence of the laser output properties of the Fe:ZnSe single crystal was investigated under ~4.04 μm laser radiation excitation in the quasi-collinear configuration. A non-selective laser cavity consisted of a flat highly reflective mirror in a range of ~3.9-5 μm and a concave (r = 200 mm) output coupler with a reflectivity of 88% in a range of ~4-5.3 μm. The pumping energy of ~9.3 mJ at ~4.04 μm in ~125 ns long pulses was applied. The angle between pumping and generated laser beam was ~20°. The maximum laser output energy of ~0.32 mJ with corresponding slope efficiency of ~7.5% was obtained at 230 K at a wavelength centred at ~4.5 μm.

We report review of mid-IR lasing in the range of ~2.1-6.05 µm from Cr ²⁺ -, Fe ²⁺ -, and Cr ²⁺ ,Fe ²⁺ -doped II-VI chalcogenides. Detailed comparison of the spectroscopic and laser properties of various laser materials enabling efficient mid-IR lasing is presented.

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.

The spectral and laser output characteristics of Cr:ZnSe single crystals optically polished at four different lengths of 2, 3, 5, and 10 mm combined with o

This paper presents the temperature dependence of the spectroscopic and laser properties of the Fe²⁺:ZnSe single crystal under excitation by radiation at a wavelength of ∼4.04µm. Excitation was supported by the Er:YAG laser (∼2.94µm) operated in the Q-switched or free-running (FR) mode that pumped the Fe:ZnSe laser cooled by liquid nitrogen to 78 K. This system generated radiation at the wavelength of ∼4.04µm. Temperature dependence of absorption, fluorescence spectra, and fluorescence decay time of Fe²⁺ ions was measured. The optimal temperature that allows efficient Fe:ZnSe laser system operation with maximum laser output energy was sought in both regimes. It was characterized at a repetition rate of 1 Hz with pulse durations of ∼175ns and ∼155µs in both modes, respectively. The highest laser output energies obtained with the crystal placed in the cryostat in gain-switched (GS) and FR modes were ∼385µJ at 260 K and ∼374µJ at 190 K, respectively. Maximum optical-to-optical efficiencies in the same modes were ∼13% at 260 K and ∼32% at 170 K, respectively. Wide laser radiation oscillation spectra depending on the temperature ranging from ∼4.3µm at 140 K to ∼4.9µm at 340 K obtained with a Gaussian-like beam spatial profile were demonstrated. Under atmospheric conditions at RT, this laser system reached a pulse energy of over 0.5 mJ at ∼4.78µm in ∼135ns pulses, which corresponds to a peak power of ∼3.9kW.