Abstract: A light-controlled light modulator can achieve high-speed, low-loss wavelength conversion. Continuous light with a wavelength &lgr;j is launched into an MMI coupler via a port, and is split into two parts by the MMI coupler, which are led to a loop-type interferometer. In the loop-type interferometer, the two parts travel separately around the loop as clockwise traveling light and counterclockwise traveling light, are combined by the MMI coupler again via a filter-equipped phase modulator, thereby being emitted to the port. In this state, signal light &lgr;i(s) with a wavelength &lgr;i is launched into the filter-equipped phase modulator via a port. Even when the wavelength &lgr;i of the signal light &lgr;i(s) is equal to the wavelength &lgr;j of the wavelength converted output light, the wavelength conversion can be achieved with preventing noise from being mixed into the output light emitted from a port.

Abstract: A method of stabilizing the frequency of a semiconductor laser comprises stabilizing a time-dependent frequency fluctuation by utilizing an optical energy absorption medium including an isotope acetylene gas molecule. An apparatus for stabilizing the frequency of a semiconductor laser, comprises a semiconductor laser, an optical energy absorption medium, a photodetector and a control circuit as essential elements. The optical energy absorption medium includes an isotope acetylene molecule.

Abstract: The present invention provides a double-cylinder type apparatus for the regeneration of active carbon, which comprises a heating furnace provided with at least one burner and at least one annular regeneration chamber composed of at least one set of an inner cylinder and an outer cylinder installed concentrically inside said heating furnace, said outer cylinder having a plurality of holes penetrating the side wall thereof, wherein the spent active carbon is supplied to the upper part of said annular regeneration chamber and the regenerated carbon is to be taken out at the lower part of the same. The heating of said annular regeneration chamber from the side of said inner cylinder is performed either by introducing the flue gas arising in said heating furnace into the inner cylinder or by providing at least one burner within said inner cylinder and utilizing the combustion gas from said burner.