Distributed reflector and wavelength-tunable semiconductor laser

摘要

A semiconductor laser comprises first and second distributed Bragg reflector diffraction gratings (10a,10b) being intervened by an active region having no diffraction grating; said first and second diffraction gratings (10a,10b) each have a plurality of repeating unit regions repeated at respective periods, thus forming respective modulation periods (Mf,Mr); in each of the repeating unit regions the length of the single period varies in the direction in which light transmits, continuously or at intervals, thereby varying the optical reflectivity of the diffraction gratings (10a,10b) depending on its position in each of its said repeating unit regions; said first and second diffraction gratings reflect light having wavelengths ( lambda 1, lambda 2,.. and lambda '1, lambda 2,...) slightly differing from each other; and said diffraction grating extends by at least two modulation periods. The application of voltages on said diffraction gratings enables coarse and fine tuning of lasing the wavelength. <IMAGE>