| 摘要 |
PURPOSE:To miniaturize size as a whole, and to monitor outgoing beams from a semiconductor laser by using a cylindrical lens made of a high index crystal as a lens employed for the coupling system of the semiconductor laser and an optical fiber and simultaneously utilizing the cylindrical lens made of the high index crystal as an external resonator for the semiconductor laser. CONSTITUTION:The parallel pencil 3 of rays propagated in a cylindrical lens 10 made of an silicon crystal is reflected partially by a flat surface 12, and the remainder is transmitted. Reflected beams return in the same optical path and are projected to a semiconductor laser 1 again, and transmitted beams are coupled with a single mode fiber terminal 6 by a condenser lens 13. The back outgoing beams 2 of the semiconductor laser 1 are received by a photodetector 14, and flowing currents are monitored, thus monitoring an output from the semiconductor laser 1. A substance between a front outgoing edge face 9 in the semiconductor laser 1 shaping an external resonator and the flat surface 12 is occupied approximately by the silicon crystal, a refractive index thereof is approximately 3.5, and external cavity length L0 required for bringing emission spectral line width to 1/100 extends over approximately 3mm. Accordingly, external cavity length L0 can be brought to 1/3 or less. |
