| 摘要 |
PURPOSE:To eliminate the malfunction of APC and the generation of back-talk noise due to return light detection by arranging an optical branching element, formed by sandwiching a polarizing film between flat plate type transparent plates, slantingly to the optical axis of a light emitting and a light receiving element. CONSTITUTION:The two both-side flat glass plates 11 between which the optical branching element 10 is sandwiched are equal in refractive index, so the element 10 can be arranged at 45 deg. to the optical axes La and Lb extending to the semiconductor laser 1 and pin photodiode 9 for collimated light. Then when the light emitted by the semiconductor laser 1 is used in the direction of a P- polarized light wave, the polarizing film 12 transmits about 80% of the light and reflects 20% of the light, and this reflected light passes through the flat plate glass 11 arranged at 45 deg. and is reflected in a direction irrelevant to the optical axis La of the semiconductor laser 1. Consequently, the generation of the back-talk noise due to the return of the reflected light to the semiconductor laser 1 is eliminated and the malfunction of the APC by a monitor element in the semiconductor laser 1 can be prevented. |
