| 摘要 |
PURPOSE:To obtain a semiconductor laser whose line width of an oscillation spectrum is sufficiently narrow and whose characteristic is excellent by a method wherein a means to reflect a high-order diffracted beam and to couple it to a laser oscillation mode and a means to control a phase of a reflected and returned beam are provided at a single-mode laser. CONSTITUTION:A diffracted beam radiated from a diffraction grating 2 progresses in a direction perpendicular to an axis of a laser resonator, is reflected by a reflector 7 formed on the surface of an epitaxial growth layer, is coupled again to the diffraction grating 2 and is coupled to a laser mode. Only when it is coupled to the laser mode in an identical phase, a narrow line width of an oscillation spectrum is obtained. Electrodes 9 are formed on the right and on the left in a phase modulation region 6; a refractive index is changed by making use of an electro-optical effect. As a result, if a phase modulation voltage of 6 V is impressed at an optical output of 20mW, a minimum line width of the oscillation spectrum of 600kHz is obtained. When a reflected and diffracted beam is in an opposite phase, the line width of the oscillation spectrum is expanded to 15MHz. A monolithic integration-type DBR-LD where a modulator is integrated can be used for a coherent communication system. |
