We describe electric-field poling of fine-pitch ferroelectric domain gratings in lithium tantalate and characterization of nonlinear-optical properties by single-pass quasi-phase-matched second-harmonic generation (QPM SHG). With a $7.5-\mathit{\mu }\mathrm{m}$-period grating, the observed effective nonlinear coefficient for first-order QPM SHG of 532-nm radiation is 9 pm/V, whereas for a grating with a $2.625-\mathit{\mu }\mathrm{m}$ period, 2.6 pm/V was observed for second-order QPM SHG of 325-nm radiation. These values are 100% and 55% of the theoretically expected values, respectively. We derive a temperature-dependent Sellmeier equation for lithium tantalate that is valid deeper into the UV than currently available results, based on temperature-tuning experiments at different QPM grating periods combined with refractive-index data in the literature.

Luminescence concentration quenching and upconversion have been quantitatively investigated in neodymium-doped ${\mathrm{LaSc}}_3({\mathrm{BO}}_3{)}_4$ (LSB) and ${\mathrm{GdVO}}_4$ (GVO) laser crystals. The microparameter of cross relaxation (self-quenching) was determined in Nd:GVO as $3.6\times {10}^{-40} {\mathrm{cm}}^6/\mathrm{s}.$ It is shown that, in Nd:LSB, upconversion is static, with the upconversion microparameter $C_{\mathrm{da}}=(0.5–1.1)\times {10}^{-37} {\mathrm{cm}}^6/\mathrm{s}.$ In Nd:GVO, upconversion is migration accelerated, with the upconversion macroparameter $\alpha \approx 1.2\times {10}^{-15} {\mathrm{cm}}^3/\mathrm{s}.$ The influence of upconversion on laser operation is discussed.

We passively Q switched a Nd:LaSc₃(BO₃)₄ microchip laser with an antiresonant Fabry–Perot saturable absorber (A-FPSA) and achieved single-frequency, 180-ps pulses with 0.1 μJ of pulse energy at a repetition rate of 110 kHz. Because of the compactness and scaling possibilities offered by the A-FPSA, the pulse width can be varied from 180 ps to 30 ns and the repetition rate from 50 kHz to 7 MHz.

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