Abstract: A short-wavelength laser light source having a semiconductor laser for emitting laser light is provided. The light source includes a power supply for driving the semiconductor laser and thereby causing the semiconductor laser to emit a fundamental wave, a polarization inversion-type light-wavelength converting device for generating from the fundamental wave a harmonic wave having a shorter wavelength than the fundamental wave; and laser light feedback means for feeding light of the fundamental wave lying in a selected wavelength region back to the semiconductor laser, thereby achieving oscillation wavelength locking. Said power supply supplies to the semiconductor laser a high-frequency power containing AC components oscillating in a cycle short enough to cause the semiconductor laser to emit the fundamental wave in the form of pulsed laser light.

Abstract: A shorter wavelength light generating apparatus consists of a semiconductor laser for initially radiating various modes of coherent light including a required mode of coherent light, a reflection type of diffraction grating for diffracting and reflecting the various modes of coherent light to selectively feed back the required mode of coherent light to the semiconductor laser which is induced by the coherent light fed back to dominantly radiate the required mode of coherent light, and an optical wavelength type of wavelength converting device for converting a part of the required mode of coherent light radiated from the semiconductor laser into shorter wavelength light. The required mode of coherent light not converted is radiated to the diffraction grating. Accordingly, even though the various modes of coherent light are initially radiated from the semiconductor laser, the required mode of coherent light is dominantly radiated from the semiconductor laser after a short time.

Abstract: A frequency doubler comprising periodic domain-inverted regions, in which a nonlinear degradation layer is formed on the surface of a waveguide, whereby the TM.sub.00 mode of the fundamental wave is converted into the TM.sub.10 mode of the high harmonic wave so as to reduce the effects of optical damage in order to stably output the TM.sub.10 mode of the high harmonic wave.

Abstract: The wavelength tolerance of a frequency doubler is enhanced so as to perform stable operation. Further, with the use of this frequency doubler, a laser source can directly modulate a laser. A waveguide and a periodic domain inverted layer are formed on an LiTaO.sub.3 substrate of -C plate, and the waveguide is divided into a plurality of zones having different propagation constants. A fundamental wave inputted in the waveguide is converted into a harmonic wave in each of the zones, and is emitted as SHG light. Parts for modulating the phases of the harmonic waves produced in the respective zones are provided between the zones.

Abstract: A wavelength conversion device exhibiting an excellent wavelength conversion efficiency is provided by forming it in such a manner that an LiTaO.sub.3 substrate is subjected to a proton exchange treatment to form a proton-exchange layer before the proton-exchange layer is subjected to heat treatment to form a domain-inverted structure. Heat treatment is performed at a high temperature rising speed to prevent the thermal diffusion of the proton-exchange layer so that the expansion of the domain-inverted structure to be formed in the proton-exchange layer is restrained. As a result, a higher harmonic wave wavelength conversion device can be provided.

Abstract: An optical harmonic generating device is provided with reverse polarization layers which are made of non-linear optical crystal polarized in a lower direction and are periodically arranged at regular intervals, a non-reverse polarization layer which is made of the non-linear optical crystal polarized in the upper direction and is arrange to surround the reverse polarization layers, a wave guide penetrating through alternate rows of the reverse and non-reverse polarization layers, a first electrode arranged on the wave guide, and second electrodes arranged on both ends of the alternate rows. Electric field is induced between the first and second electrodes through the wave guide to change a refractive index of the reverse and non-reverse polarization layers.

Abstract: A short-wavelength light generating apparatus comprising a pumping semiconductor laser and an intra-cavity solid state laser, the intra-cavity solid state laser is excited in response to a laser light beam from the semiconductor laser to generate a short-wavelength light beam to an external. Also included in the apparatus is an external grating mirror having on its one surface a reflection type diffraction grating and placed between the semiconductor laser and the intra-cavity solid state laser. The external grating mirror reflects the laser light beam from the semiconductor laser to feedback a portion of the laser light beam to said semiconductor laser so that an oscillated wavelength of the semiconductor laser becomes within a wavelength acceptance of the intra-cavity solid state laser. Further, the external grating mirror supplies a portion of the laser light beam from the semiconductor laser to the intra-cavity solid state laser. This arrangement can output a stable harmonic wave with a high efficiency.

Abstract: A frequency doubler of the invention employs a nonlinear optical effect of stabilizing the harmonic output from the frequency doubler. The frequency doubler has an LiNbO.sub.3 substrate, domain inverted regions and a waveguide, which are formed on the substrate, and a thin-film heater formed on the waveguide by depositing Ni-Cr. The temperature of the frequency doubler is controlled by applying a current to the thin-film heater so as to heat the frequency doubler. Even if the wavelength of a semiconductor laser is changed due to change in the environmental temperature, the frequency doubler can stably be operated by changing the temperature of the frequency doubler.

Abstract: A wavelength conversion device exhibiting an excellent wavelength conversion efficiency is provided by forming it in such a manner that an LiTaO.sub.3 substrate is subjected to a proton exchange treatment to form a proton-exchange layer before the proton-exchange layer is subjected to heat treatment to form a domain-inverted structure. Heat treatment is performed at a high temperature rising speed to prevent the thermal diffusion of the proton-exchange layer so that the expansion of the domain-inverted structure to be formed in the proton-exchange layer is restrained. As a result, a higher harmonic wave wavelength conversion device can be provided.

Abstract: A tapered light wave guide reduced in propagation loss, improved in coupling efficiency and free from the problem of optical damage. An input section, a widthwise tapered coupling section having a depth d2, and a wave guide having a depth d1 are formed on an LiNbO.sub.3 substrate. A depthwise tapered section in which the depth is changed from d2 to d1 is provided to connect the widthwise tapered coupling section having constant depth d2 and the wave guide, whereby a reduction in light propagation efficiency due to optical damage is prevented.