PURPOSE: To change over a main semiconductor laser to a spare semiconductor laser in a very short time by integrating a Y branch element for introducing the main laser, the spare laser and output beams to one optical guide on the same semiconductor substrate.
CONSTITUTION: A p-InP clad layer 2, an InGaAsP active layer 3, an n-InP clad layer 4 and a p-InGaAsP layer 5 are grown in a groove in a semi-insulating InP substrate 1. A Y branched waveguide and an FET gate section are processed through photolithography. A grating 8 for Bragg reflection is formed to one part of the clad layer 4. Photodiodes 6, 7 use the layer 5 as the anode side and the layer 4 as the cathode side, and detect the intensity of beams projected to a p-n junction surface. Laser diodes (LD)10, 11 are constituted by the clad layer 4, the active layer 3, the clad layer 2, gratings 8, 9 and cleavage planes 12. One side of a resonator is formed in the cleavage plane 12, and laser beams are projected to a collective waveguide 17 from the Y type branch line 14. FETs 18, 19 modulate and drive the LDs 10, 11.
MATSUOKA HARUJI
OKAMOTO KENJI
