Distributed Bragg reflector laser null for frequency modulation

摘要

PURPOSE: To select a Bragg wavelength longer than the characteristic wavelength of a gain medium by frequency modulating a distributed Bragg reflector laser having a feedback structure in frequency modulation transmitter for a light wave system. CONSTITUTION: A guide layer 26, an active layer 27, and a ptype four element cap layer 29 are formed sequentially on a substrate 23 and an isolation trench 32 is made in a part of a heterostructure for the purpose of electric isolation between a Bragg reflective region and a gain region. The feedback structure of the laser includes a corrugated lattice 31 formed in the guide layer 26. A lattice period effective on the guide region of the laser in the Bragg reflector region is determined according to formula I. In the formula I, Λeff is an effective period, λp is the substantial gain peak or the characteristic wavelength at maximum gain for the gain region of semiconductor structure, M is the order of the lattice of 1 or above, and n is the modal or effective refractive index for the waveguide mode of the semiconductor laser. According to the structure, the laser is controlled to emit a light wave signal having Bragg wavelength longer than the characteristic wavelength of the laser.