PURPOSE: To make it possible to generate high-efficiency and stable long-lived higher harmonics of a laser beam by a method wherein a higher harmonics generating means and the laser beam are relatively changed in the direction perpendicular almost to the optical path of the laser beam.
CONSTITUTION: In a device, which is provided with a laser light source 1 and a nonlinear optical crystal 4 to generate higher harmonics of a laser beam LB and generates the higher harmonics SH of the laser beam LB by irradiating the beam LB on the crystal 4, the device is provided with an oscillation mirror 2, by which the crystal 4 ahd the beam LB are relatively changed in the direction perpendicular almost to an optical path of the beam LB. The beam LB and the higher harmonics SH of the beam LB are absorbed in the crystal 4, whereby heat which is generated is equally generated and a temperature distribution in the crystal 4 does not become steep and the intensity of the beam LB, which is irradiated per unit area of the crystal 4, is reduced as seen in unit time. Thereby, while the generation efficiency of the higher harmonics SH is kept almost constant, the lifetime of the nonlinear optical crystal can be prolonged.
HARA HIDEO
ICHIHARA YUTAKA
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