Laser diode with an external grid in a waveguide

摘要

PURPOSE: A tunable laser device is provided to improve a transmission characteristic and perform a channel switching operation by using an inexpensive Fabry-Perot laser and a sampled grating or a multiple-overlapped grating formed on a planar lightwave circuit. CONSTITUTION: A Fabry-Perot laser(220) is formed on one side of a semiconductor substrate(210). The Fabry-Perot laser includes a plurality of longitudinal modes. A planar lightwave circuit(240) is formed on the other side of the semiconductor substrate. The planar lightwave circuit includes a waveguide and a clad surrounding the waveguide. A grating having a multi-reflection spectrum is formed on a part of the waveguide. An output beam of the Fabry-Perot laser is combined with the waveguide. The grating is used for reflecting plural beams having different wavelengths. The Fabry-Perot laser is wave-locked by one of the beams reflected by the grating.