| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To obtain a UV laser beam suitable for a precision fabrication by enhancing the conversion efficiency of the laser beam when the wavelength of the laser beam is converted to generate harmonic waves at <355 nm wavelength in a wavelength conversion element consisting of a lithium tetraborate single crystal. <P>SOLUTION: The wavelength conversion element is heated while controlling and kept at a specified temperature (e.g. 200°C) in the temperature range from 200 to 450°C. The temperature accuracy is controlled to±0.3°C, preferably±0.1°C. The two-photon absorption in the lithium tetraborate single crystal decreases by heating the wavelength conversion element. Therefore, even when the intensity of the incident light is increased, transmittance for the laser beam hardly decreases, which improves the conversion efficiency for the laser beam. As heat generation caused by two-photon absorption is suppressed, a problem that the refractive index changes to degrade phase matching can be avoided, loss or an unstable state in the output can be prevented and the quality of the beam can be maintained. <P>COPYRIGHT: (C)2004,JPO&NCIPI</p> |
