The principal refractive indices and the thermal coefficients for a LiNbO(3) crystal doped with 5 mol. % MgO have been measured by a minimum-deviation method for the wavelengths of 0.53975, 0.6328, 1.0795, and 1.3414, microm in the temperature range 20-154.5 degrees C. The constants of modified Sellmeier equations are all given in the described temperature range. The measured results were used to calculate the type I critical phase-matching angles for 1.0795- and 1.3414-microm second-harmonic generation at room temperature and the noncritical phase-matching temperature for 1.0795-microm second-harmonic generation for LiNbO(3) crystal doped with 5 mol. % MgO. The values obtained agree well with the experimental results.

The possibility of simultaneous multiple wavelength lasing in various neodymium host crystals such as Nd:YAG, Nd:YLF, Nd:BEL, and Nd:YAP has been analyzed by the ‘‘oscillation condition.’’ It is shown that this kind of laser can be realized in all the described crystals in pulsed state, but only achieved in the Nd:YAP crystal in continuous-wave state. On the basis of the analyzed results, we have achieved cw simultaneous multiple wavelength lasing in Nd:YAP crystal for the first time at both 1.0795 and 1.3414 μm.

The principal refractive indices of yttrium aluminate crystal doping with 1-wt.% neodymium (Nd:YAP) have been measured by a minimum deviation method for the wavelengths 0.5398, 0.6328, and 1.0795 microm in the temperature range of 289-435 K. The thermal refractive index coefficients have been obtained at these wavelengths, and they are all positive and slightly decrease with increased wavelength. The constants of the single term Sellmeier equation are also given for the 273-420 K temperature range. These constants are in linear relationship with temperature in the 4 x 10(-3) error range.