Abstract: A garnet-type single crystal is represented by a general formula, A3B2C3O12 (having a crystal structure with three sites A, B and C occupied by cations, wherein A represents an element occupying the site A, B represents an element occupying the site B, C represents an element occupying the site C, O represents an oxygen atom), and contains fluorine, in which the fluorine attains any one or both of substituting for the oxygen atom or compensating for oxygen defect.

Abstract: A garnet-type single crystal is represented by a general formula, A3B2C3O12 (having a crystal structure with three sites A, B and C occupied by cations, wherein A represents an element occupying the site A, B represents an element occupying the site B, C represents an element occupying the site C, O represents an oxygen atom), and contains fluorine, in which the fluorine attains any one or both of substituting for the oxygen atom or compensating for oxygen defect.

Abstract: The present invention provides a Yb-doped crystal for a solid state laser, wherein a main active element of the Yb-doped crystal comprises Yb.sup.3 +. The Yb-doped crystal for a solid state laser is prepared by increasing a ratio of Yb.sup.3 + to Yb.sup.2 + in a Yb-doped material by a heat treatment to the Yb-doped material in an oxidizing atmosphere, and carrying out a crystal growth of the Yb-doped material.

Abstract: An Er:YVO.sub.4 laser oscillator has an excitation light source constituted by a laser diode and a medium constituted by an Er:YVO.sub.4 crystal in which Er.sup.3+ ions are activators and YVO.sub.4 is a host material. The oscillation light is perpendicular or parallel to c-axis of the crystal. The laser operates in target wavelengths on energy transitions of the Er.sup.3+ ions, the target wavelengths being 510 nm to 590 nm, 840 nm to 870 nm, 970 nm to 1020 nm, and 1450 nm to 1700 nm. The crystal is coated with a TiO.sub.2 --SiO.sub.2 system high reflection mirror coating and a fluoride megnesium-zeolite system antireflection coating corresponding to the target wavelengths and a fluoride megnesium-zeolite system antireflection coating corresponding to the wavelength of the laser diode. These coatings together with an output mirror constitute a resonator. For manufacturing the crystal, Er.sub.2 O.sub.3, Y.sub.2 O.sub.3, and V.sub.2 O.sub.

Abstract: An optical polarizer/analyzer incorporated in an optical device is formed of an yttrium vanadate represented by the molecular formula of YVO.sub.4, the yttrium vanadate is as large in differential refractive index between an ordinary ray and an extraordinary ray and in optical absorption characteristics as rutile but is smaller in invertion loss than rutile at 1.3 micron wavelength and the yttrium vanadate is easy for producing a rod with a large diameter, so that the optical polarizer/analyzer of the yttrium vanadate is suitable for the component element of an optical device.

Abstract: Iron is close to a major surface layer of a yttrium aluminate laser rod so that the layer portion may have a filtering effect. The absorption factor for the short wavelength light of this layer portion depends upon the concentration c (weight percent) of the contained iron and the thickness t (.mu.m) of the iron-containing layer. Consequently, the effect of the iron in the laser rod can be evaluated as a function of the product c.times.t (wt%..mu.m) of the concentration c and the thickness t. In the range of the product c.times.t of 1<c.t<2.times.10.sup.2, a laser output could be obtained which is higher than that of the conventional laser rod not containing iron jointly with a short wavelength light filter. The thickness of the iron-containing layer is 1/4 or less of the radius of the laser rod.

Abstract: A laser device includes a solid state laser element consisting of a yttrium aluminate crystal and a source of pumping light. A light filter which intercepts and removes pumping light components having wave-lengths below about 5,000A is disposed between the laser element and the light source. The removal of these selected higher frequency components lowers the oscillation threshold value and increases the laser output.