WAVELENGTH CONVERSION OPTICAL ELEMENT, METHOD FOR MANUFACTURING WAVELENGTH CONVERSION OPTICAL ELEMENT, WAVELENGTH CONVERTER, ULTRAVIOLET LASER IRRADIATION DEVICE AND LASER MACHINING SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a wavelength conversion optical element in which output characteristics are increased according to incident intensity and which is usable at room temperature. SOLUTION: The wavelength conversion optical element contains cesium-lithium-borate based crystals and wherein the content of water impurities in the crystals is not related to a polarizing direction and equal to or more than 1% in an actual measurement value without considering the loss on the optical polishing surface by using transmissivity (Ta) of 3589 cm-1in an infrared transmission spectrum of the optical element as an index when the crystals are processed to the optical element with orientation of fourth-harmonic generation of an Nd:YAG laser and with a length of 10 mm. COPYRIGHT: (C)2007,JPO&INPIT