Abstract: The present invention provides a waveguide type optical switch which has a high extinction ratio and can be driven efficiently at a low voltage or a low current injection. Where the waveguide type optical switch is used as a reflection type optical switch, the switch section is of current confinement structure, and where it is used as a directional coupler type optical switch, the pn junction is formed in the position where the optical electric field takes the maximum value for the fundamental mode of the light propagating in the waveguide.

Abstract: A distributed feedback semiconductor laser provided with a grating which effects optical feedback by means of periodic corrugation disposed inside an optical resonator. The optical resonator has at least two regions having different Bragg wavelengths, and these regions are arranged longitudinally in the direction of an optical axis. The laser device can realize stable single longitudinal mode oscillation through variation of the refractive indexes of the regions nonuniformly around an average value.

Abstract: An optical waveguide obtained by forming on a substrate an amorphous silicon film which contains a predetermined quantity of at least one of the elements of hydrogen, nitrogen and oxygen so that the amorphous silicon film has a predetermined value of refractive index. The optical waveguide can be made easily by carrying out a sputtering operation, in which Si is used as a target with a mixed gas of argon and at least one of hydrogen, nitrogen and oxygen, or a mixed gas of hydrogen and at least one of nitrogen and oxygen used as a sputtering gas, the composition of the sputtering gas being controlled in a predetermined manner during the sputtering operation.