Narrow linewidth semiconductor laser

Abstract

A novel narrow linewidth laser device is disclosed that is formed monolithically on a semiconductor substrate, such as an indium phosphide substrate, that includes a continuous waveguide with a gain section and a grating section wherein a grating is constructed so that its power reflectivity profile has a ratio of reflectivity slope over reflectivity at the 3 dB point below the reflectivity peak on the red side (longer wavelength side) of the grating larger than a value of 2/nm. The operating wavelength of the device may be tuned thermally, electrically, or thermo-electrically to be on the red side of the fiber Bragg grating reflectivity profile, preferably at the 3 dB point below the reflectivity peak or lower. In another embodiment, a second grating is formed on a second grating section of the waveguide on the opposite side of the gain section than the first grating section and wherein the reflectivity profile of the second grating overlaps at least a portion of the reflectivity profile of the first grating.