PROBLEM TO BE SOLVED: To provide a coherent light source for UV light which is high in efficiency and simple in device constitution.;SOLUTION: The light of a wavelength 1,554 nm emitted from a semiconductor laser 100 is amplified by an erbium-doped fiber 106 and is made incident on a nonlinear optical crystal LBO 110 by a lens 109 and the light 111 of a wavelength 772 nm which is a second optical harmonic is generated. The light 111 of the wavelength 772 nm is condensed to a nonlinear optical crystal LBO 113 by a lens 112 and is converted into a light of a wavelength 386 nm by second optical harmonic generation. The light 114 of a wavelength 386 nm is condensed to a pseudo phase matching crystal 116 by a lens 115 and is converted to the light 111 of a wavelength 193 nm by second optical harmonic generation. When the pseudo phase matching of first order is attempted to be carried out in this case, the period of polarization inversion is about 0.95 m. In this case, too, there is no Walk-Off effect and the second optical harmonic generation of good beam quality with high efficiency is possible.;COPYRIGHT: (C)2002,JPO
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