| 摘要 |
PURPOSE:To obtain an optical system for a semiconductor laser which reduces light noises and stabilizes its oscillation wavelength at the same time and facilitates a position adjustment by using a distributed index lens which has a reflection increasing film formed on its projection surface as an optical element which converts divergent light into nearly parallel luminous flux. CONSTITUTION:The divergent light radiated by the semiconductor laser 1 is made incident on the distributed index lens 2 and projected from this lens 2 as parallel luminous flux, but part of the light is fed back to the semiconductor laser 1 because of the presence of the reflection increase film 3. The reflection factor P of the reflection increase film 3 is so determined that the quantity of feedback light is >=1%, and then the purpose of light noise reduction is attained. On the other hand, the reflection factor Q of the reflection increase film 3 should be equal to or larger than that of the laser end surface so that the reflection increase film 3 and the laser end surface of the semiconductor laser 1 constitute an external resonator. For the purpose, the reflection factor P and reflection factor Q are compared with each other and the larger reflection factor is set as the reflection factor of the reflection increase film 3 to reduce light noises and stabilize the wavelength at the same time.
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