| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical communications system that branches light large enough to control an optical output of a semiconductor laser to a light- receiving device for monitoring, stabilizes the optical output, and has high reliability and high efficiency. SOLUTION: A laser chip is a surface light-emitting type semiconductor laser device chip that has an oscillation wavelength of 1.1μm to 1.7μm and a resonator structure including a reflector provided on top and bottom parts of an active layer to produce laser light. The reflector is a semiconductor distributed Bragg reflector in which material layers constituting the reflector have refractive indexes changing periodically between a small value and a large value and reflect entering light by optical wave interference. The material layer having a small refractive index contains Alx Ga1-x As (0<x<=1) and the material layer having a large refractive index contains Aly Ga1-y As (0<=y<x<=1). Here, the optical output of the semiconductor laser is controlled by the use of the output of the light-receiving device for monitoring. In a branching means for branching the optical output, a light transmittance in a usable wavelength band is not less than 1% and not more than 50% and there are provided a plurality of independent light-receiving devices.
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