Optical wavelength conversion method, optical wavelength conversion system, program and medium, and laser oscillation system

In an optical wavelength converting method in which light from a laser oscillator that oscillates coherent light of an inherent wavelength lambda is employed as incident light, and is made to input to a nonlinear optical crystal, and light having a wavelength of 1/2 lambda is radiated, the wavelength of the incident light is 1000 nm or less, and the peak power density of the incident light is 0.1-10 fold greater than the peak power density that provides the maximum conversion efficiency. The nonlinear optical crystal is heated to and maintained at 200-600 DEG C. An optical wavelength converting method, and a program therefor are provided that achieves high conversion efficiency stably using an nonlinear optical crystal, enabling manufacture of an all solid state ultraviolet laser oscillator that is durable with respect to practical application. Prescribed fundamental waves are input to a first crystal and a second crystal sequentially. The first crystal has a higher bulk damage threshold value with respect to the fundamental waves than that of the second crystal. The second crystal has a higher effective nonlinear constant with respect to the fundamental waves than that of the first crystal. An optical wavelength converting method, optical wavelength converting system and a laser oscillating system are provided that enable high power second harmonics to be obtained with good efficiency.