Abstract: In an optical wavelength converting method in which light from a laser oscillator that oscillates coherent light of an inherent wavelength ? is employed as incident light, and is made to input to a nonlinear optical crystal, and light having a wavelength of ½? 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° C. 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.

Abstract: An ultraviolet laser is provided that increases the conversion efficiency of laser beams when harmonics having wavelengths of less than 355 nm are generated by converting laser beams with a wavelength conversion element made of a single crystal of lithium tetraborate. A wavelength conversion element is heated and controlled to a specific temperature (for example, 200° C.) within a temperature range of 200 to 450° C. with a predetermined temperature precision.

Abstract: A nonlinear optical conversion device includes a nonlinear crystal having entrance and exit surfaces allowing input and output laser beams to propagate in the phase-matching plane for a desired nonlinear generation process. The nonlinear generation process involves a nonlinear interaction in the nonlinear crystal and resultant conversion of power in one or two input beams into power in the output beam. The nonlinear crystal is characterized by absorption and resultant modification of the crystal properties by the power in the output beam, the modification with the potential for reducing the efficiency of the nonlinear process in the crystal, and the nonlinear process involving critical phase-matching in the nonlinear crystal in which the powers in the output beam and input beam or beams propagate in different directions through the process of Poynting vector walk-off. The input beam or beams are of a sufficiently small beam dimension in the phase-matching plane.

Abstract: An ultraviolet laser is provided that increases the conversion efficiency of laser beams when harmonics having wavelengths of less than 355 nm are generated by converting laser beams with a wavelength conversion element made of a single crystal of lithium tetraborate. A wavelength conversion element is heated and controlled to a specific temperature (for example, 200° C.) within a temperature range of 200 to 450° C. with a predetermined temperature precision.

Abstract: In an optical wavelength converting method in which light from a laser oscillator that oscillates coherent light of an inherent wavelength &lgr; is employed as incident light, and is made to input to a nonlinear optical crystal, and light having a wavelength of ½ &lgr; 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° 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.

Abstract: A borate single crystal which can stably perform light wavelength conversion with high efficiency down to the ultraviolet region is represented by the chemical formula (A2O).(B2O3)x, and is an orthorhombic crystal belonging to the P212121 space group, wherein A includes two elements selected from the group consisting of Li, Na, K, Rb, and Cs, and 1.5<x<2.5.