| 摘要 |
PURPOSE:To provide a semiconductor laser for optical FM which operates stably by dividing DFB laser to four parts, by coupling each part through lambda/4 phase shift, and by applying thereto uniform bias current and fixed modulation current whose sign is reverse in quadrupole. CONSTITUTION:DFB lasers 101-104 are adhered closely each other and modulation of active layer width to provide each distribution feedback is composed so that its phase deviates by 1/2 wavelength. A fixed current not less than the threshold is made flow to each of electrodes 5, 6 for laser oscillation and dissimilar modulation current is further applied to each of the electrodes 5, 6. The carrier density of the first active layer 1 of each of DFB lasers 101-104 thereby changes. Optical wave between regions of DFB lasers 101-104 receives lambda/4 phase shift. When injected current changes, the amplitude of input/output light and optical frequency also generally change. Current modulation which has reverse sign and equal amplitude are applied to the first - fourth DFB lasers 101-104, that is, I, IV regions and II, III regions of I-IV regions. |
