The absorption by the mirrors of a laser operating under conditions of intracavity frequency doubling has been studied by photothermal radiometry. The absorption coefficient of the mirror for the fundamental wavelength increases when the second harmonic is incident on the mirror. The photoinduced absorption depends on the type of coating and on the intensity of the second harmonic.

Color centers were observed in nonlinear KTiOPO4 (KTP) crystals under conditions of second harmonic generation (SHG) of λ = 1.064 μm neodymium laser radiation at power densities > 100 MW/cm2. The additional absorption at the SHG wavelength (λ = 0.532 μm) reduced the efficiency of conversion of the laser radiation frequency in KTP crystals and their optical strength at the second harmonic wavelength.

In nonlinears KTiOPO4 (KTP) crystals color centers have been found under the generation of the second harmonic of the neodymium laser radiation at the wavelength lambda = 1.064-mu-m at the power density higher than 100 MW/cm2. An additional absorption at the SHG wavelength (lambda = 0.532-mu-m) which arises as a result of the color center formation reduces the efficiency of the laser radiation conversion in KTP crystals and their stability to the second-harmonic radiation.

A comparative study was made of amplification of radiation emitted from YSGG:Cr:Nd, YLF:Nd, and YAG:Nd crystal lasers in a single-pass amplifier utilizing LGS-32 phosphate glass. The results indicated that a YSGG:Cr:Nd crystal laser was a promising master oscillator for the use in combination with phosphate glass amplifiers.

Low-threshold wide-band lasing was achieved for a YAG crystal with optically and thermally stable color centers. The absorption and luminescence spectra were determined, and the gain was measured in the range of wavelengths corresponding to the color-center luminescence. The cross section of the lasing transition was estimated (8 × 10−19 cm2) and the efficiency of conversion of the pump radiation from a neodymium laser into the output radiation was determined (10%).

A high-efficiency solid-state (YAG:Nd3+) source was constructed. It was capable of emitting visible and infrared radiation when pumped by a laser diode. The cw output power was 80 mW at a wavelength of 0.53 μm when the electrical pump power was 3.2 W and this corresponded to an efficiency of 2.5%.

Spectral, luminescence, and lasing characteristics of gadolinium scandium aluminum garnet doped with chromium and neodymium, S A Bolshakov, V M Garmash, V A Zhitnyuk, L A Ermakova, A G Okhrimchuk, L N Raiskaya, M R Syrtlanov, O G Siyuchenko, P A Tseĭtlin, A V Shestakov

A miniature source of coherent ultraviolet radiation was constructed on the basis of a YAG:Nd3+ laser pumped by a semiconductor laser. The average power of the output radiation at λ = 0.355 μm was 0.32 mW when the electrical pump power was 3.2 W (the pulsed output radiation power was 5 W, the pulse duration was 5 ns, and the pulse repetition frequency was 12.8 kHz).