Abstract: The present invention is to provide a method of compensating the wavelength dependence of birefringence of an optical part (B) which comprises using a film (a) made of a (co)polymer (?) obtained from at least one olefin selected among 4-methyl-1-pentene, 3-methyl-1-pentene, and 3-methyl-1-butene as a (co)monomer ingredient.

Abstract: A ferroelectric substrate periodically poled structure manufacturing method for periodically reversing the polarization direction by applying an electric field between electrodes on the both surfaces of the ferroelectric substrate. An electric field is applied to a portion between the electrodes in a direction different from the spontaneous direction. Next, a step of applying the electric field in the same direction as the spontaneous polarization is performed at least once. After this, the electric field is applied in the direction different from the spontaneous polarization.

Abstract: A wavelength conversion apparatus includes: multiplexer that multiplexes pumped light and signal light; wavelength conversion element that wavelength-converts linearly polarized light components in x direction with respect to the pumped light and the signal light, and generates output light polarized in x direction; and light circulator that allows the light of the multiplexer to be output to the wavelength conversion element and allow the light from the wavelength conversion element to be output to the port; reflecting mirror; and Faraday rotator that makes a polarization direction difference of 90 degrees between light traveling from the wavelength conversion element to the reflecting mirror and light reflected at the reflecting mirror so as to return to the wavelength conversion element. Intensity IL of the output light does not depend on the incident polarization angle &phgr; of the signal light &lgr;s and is constant.

Abstract: A wavelength conversion apparatus includes: multiplexer that multiplexes pumped light and signal light; wavelength conversion element that wavelength-converts linearly polarized light components in x direction with respect to the pumped light and the signal light, and generates output light polarized in x direction; and light circulator that allows the light of the multiplexer to be output to the wavelength conversion element and allow the light from the wavelength conversion element to be output to the port; reflecting mirror; and Faraday rotator that makes a polarization direction difference of 90 degrees between light traveling from the wavelength conversion element to the reflecting mirror and light reflected at the reflecting mirror so as to return to the wavelength conversion element. Intensity IL of the output light does not depend on the incident polarization angle &phgr; of the signal light &lgr;s and is constant.

Abstract: An object of the invention is to provide a laser light generating apparatus capable of minimizing loss in a resonator to give a high efficiency of wavelength conversion. A resonator comprises two reflecting mirrors 1 and 2 arranged in linear relationship and a non-linear optical crystal 3 disposed in the resonator. The non-linear optical crystal 3 is formed in a trapezoid shape so that a pair of input and output sides opposite to each other are tilted with respect to the optical propagation axis. The fundamental laser light is introduced along the optical propagation axis into the optical resonator, converted to a second harmonic by the non-linear crystal 3, and released outside from the reflecting mirror 2. It is made possible to adjust the beam diameter and convergence angle of the laser light on the light incidence plane(Y-Z plane) when the laser light passes the input and output sides of the non-linear optical crystal 3.

Abstract: A short wavelength light source mainly comprises a semiconductor laser for pumping a laser medium, a birefringence filter for controlling or stabilizing the waveform by applying an optical feedback to the semiconductor laser to feed back only light of specific wavelength, lens systems for focusing the pumping light, and an optical resonator composed of a laser medium formed of Nd:YAG doped with 1% of Nd and a nonlinear optical element formed of KNbO.sub.3. The birefringence filter is structured as a Lyot filter, and is composed of a birefringence element made of 2 mm thick non-doped YVO.sub.4, a polarizer, and a birefringence element made of 4 mm thick non-doped YVO.sub.4.This constitution realizes a short wavelength light source achieving a single longitudinal mode oscillation while maintaining a high output, small in size, superior in efficiency, and excellent in wavelength stability.