Abstract: A substrate with an optical waveguide includes a substrate having a through hole and two sides, a first optical waveguide defined in the though hole of the substrate so as to linearly extend between both sides of the substrate, a second optical waveguide defined on at least one of the sides of the substrate, and direction changing means for changing a transmitting direction of a light signal from either one of the first and second optical waveguides to the other. Each optical waveguide includes a core layer for transmitting the light signals and a clad layer formed around the core layer.

Abstract: In spectrum measuring equipment the light to be measured is separated by a double-image polarizing element into two polarized wave components whose planes of polarization cross each other perpendicular and which have different optical axes. The two polarized wave components are applied to a dispersing element so that their planes of polarization intersect the direction of light separation at .+-.45.degree. thereto, respectively. The sum of optical powers of the two polarized wave components separated by the dispersing element is measured by a photodetector, so that spectrum measurement independent of the polarization of the light to be measured can be achieved.

Abstract: Spatial phase modulating transparent masks comprising two or more portions having two different optical paths and their production processes are disclosed. The transparent masks are particularly useful as an exposure mask in the production of phase-shifted, distributed feedback (DFB) semiconductor lasers for a single-mode operation. A process for the formation of phase-shifted diffraction gratings or corrugations which comprises exposing a substrate, through the above transparent mask, to exposure radiation is also disclosed. According to the present invention, the phase-shifted diffraction gratings can be easily and directly produced with a high accuracy and reliability.

Abstract: An optical switch comprising: an electrode-optic crystal substrate (1, 1'); a central waveguide (21); a pair of input waveguides (22, 23), and a pair of output waveguides (24, 25). A refractive-index-changed region (R') is provided symmetrically within some part of the central waveguide. Switching from the straight-through state to the branching state or vice versa is carried out by introducing a change in the refractive index of the index-changed region.

Abstract: Disclosed is a laser light source device having a laser and an external resonator, wherein as a base, a Faraday rotator is provided at the laser side front of a reflection plane of the resonator so that clockwise and counter-clockwise circular polarizations which have frequencies slightly different to each other are generated, and if a laser such as a semiconductor laser having an eigen-mode having a linear polarization is applied, elements which rotate a polarization by 90 degrees by one emission-and-return through the element, for example, quarter-wave plates, are arranged, The device does not need a strong magnetic field or a strong electric field, and can easily generate lights which are a constant strength. Thus the device can be miniaturized and a high efficiency obtained.