| 摘要 |
PURPOSE:To afford sufficient monitoring function even for the minute change of a laser oscillating wavelength by monitoring the oscillation conditions of a semiconductor laser by using a waveguide type branching filter which has wavelength selection and reflection functions and a photodetector. CONSTITUTION:The oscillated output light of a DFB laser is coupled to a light waveguide 3 which is directly coupled to an edge face. An InGaAsP layer of a composition which has a transparent band gap against laser light is used for the light waveguide. Part of the oscillated output light propagated in a light waveguide layer is diffracted by a grating 4 at an angle which satisfies Bragg condition. If the diffracted light of a steady state oscillation wavelength is entered in a photodetector 5, the diffracted light passes through a transparent characteristic buried region and is detected by the photo detector 5. If the oscillated wavelength of the laser is changed by an external factor, the Bragg condition by the grating 4 is changed and the incident condition to the photodetector is changed so the stabilizing of an absolute oscillation wavelength is contrived by monitoring each output of the photodetectors provided at an interval and by feeding the outputs of the photodetectors back to a control system. |
