Abstract: An optical device is capable of changing signal light to a plurality of paths. The device includes a film, a heating source attached to the film, and a heat radiator plate attached to the other portion of the film. The refractive index of the film varies according to heat excitation, and the film comprises crystal grains of an oxide and amorphous portions present between the crystal grains.

Abstract: An optical switch, in which focal position of beams is adjusted to provide a high switching efficiency and a high stability in action without increasing a light source output of a control light, comprising a condensing means for making a signal light and a control light convergent and incident upon a nonlinear optical thin-film and wherein irradiation of the control light causes a change of the nonlinear optical thin-film in refractive index to thereby change the signal light into a transmitted light or a reflected light to take out the same as an output signal.

Abstract: It is an object of the present invention to provide a reflector made of heat-resistant glass. It is another object of the present invention to provide a projective display which uses the reflector. A projector device having: a light source emitting white light; a reflector reflecting a light emitted from the light source; a light valve modulating illumination beam of light; and a projective lens projecting image light from the light valve, wherein the reflector is made of a glass containing SiO2 as a major ingredient and at least one rare-earth element selected from the group consisting of Sc, Y, La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and the glass has a thermal expansion coefficient lower than 40×10?7/° C. and a transition temperature higher than 500° C.

Abstract: An optical device is capable of changing signal light to a plurality of paths. The device includes a film, a heating source attached to the film, and a heat radiator plate attached to the other portion of the film. The refractive index of the film varies according to heat excitation, and the film comprises crystal grains of an oxide and amorphous portions present between the crystal grains.

Abstract: A non-linear optical material comprising crystal grains of an oxide having a corundum type crystal structure, and amorphous portions in the surroundings of the crystal grains, in a thin film, is disclosed. The non-linear optical thin film has such a property that its refractive index varies largely when energy is applied thereto. Since the material shows little loss of light transmitted therethrough, it is possible, by use of the material, to provide a non-linear optical device for efficiently changing over the emission path of a light signal or turning-ON/OFF the light signal.

Abstract: An optical switch, in which focal position of beams is adjusted to provide a high switching efficiency and a high stability in action without increasing a light source output of a control light, comprising a condensing means for making a signal light and a control light convergent and incident upon a nonlinear optical thin-film and wherein irradiation of the control light causes a change of the nonlinear optical thin-film in refractive index to thereby change the signal light into a transmitted light or a reflected light to take out the same as an output signal.

Abstract: A non-linear optical material comprising crystal grains of an oxide having a corundum type crystal structure, and amorphous portions in the surroundings of the crystal grains, in a thin film, is disclosed. The non-linear optical thin film has such a property that its refractive index varies largely when energy is applied thereto. Since the material shows little loss of light transmitted therethrough, it is possible, by use of the material, to provide a non-linear optical device for efficiently changing over the emission path of a light signal or turning-ON/OFF the light signal.