We report on cavity-enhanced second-harmonic generation of 488 nm radiation in a 5 mm long periodically poled KTiOPO4 (PPKTP) crystal pumped by the output of a single-mode 976 nm semiconductor external cavity laser. At a pump laser output power of 660 mW, a mode-matching efficiency into an enhancement cavity of 65 % was observed. A maximum power of 156 mW at 488 nm was generated in the enhancement cavity of which 130 mW was coupled out. Under these pump laser conditions an overall optical conversion efficiency of 20 % and an overall electrical to optical efficiency of 9 % was measured. Both the spatial and spectral properties of the 488 nm beam are of very high quality. Typically, a near-diffraction-limited beam with M<sup>2</sup><1.1 is produced with low astigmatism and little ellipticity.
Bulk single crystals up to 20 mm in diameter and 40 mm long for LiInS<SUB>2</SUB> and up to 10 mm, 20mm, respectively, for LiInSe<SUB>2</SUB> have been grown. Their color changed from colorless to rose for the first one and from yellow to dark red for the other. All crystals have wurtzite-type lattice, lattice parameters were determined. A band gap was found to be 3.72 and 3.57 eV for LiInS<SUB>2</SUB> and 3.02, 2.86 eV for LiInSe<SUB>2</SUB> at 80 and 300K respectively. Color variations are due to point defects, first of all to interstitial sulfur, resulting in additional wide absorption bands in the shortwave part of transparency range. For LiInS<SUB>2</SUB> the SHG phase matching conditions were found to be similar for samples of different color and some difference from Boyd's predictions of 1973 was shown.