Image Number 2 for United States Patent #5790579.
A pulsed semiconductor laser has a lower threshold current and a more stable pulse train. The structure includes a saturable absorber section has a quantum well structure for laser oscillation, a gain section, a phase control section, and a super structure grating-distributed Bragg reflector section. It uses an improved construction for overcoming problems of conventional pulsed semiconductor lasers. The improved structure includes five quantum well layers having thicknesses with respective spontaneous emission peak wavelengths of ".lambda.-2.delta.", ".lambda.+.delta.", ".lambda.+2.delta.", ".lambda.", ".lambda.-.delta." at room temperature from their upper section. .lambda. denotes the mean wavelength of the oscillating pulse laser, and .delta. denotes a fixed value less than 12 nm. The super structure grating-distributed Bragg reflector section has five sampling sections, with each section having five kinds of different pitches arranged in order of thicknesses of 25 cycles, 5 cycles, 25 cycles, 5 cycles, and 25 cycles.