| 摘要 |
PROBLEM TO BE SOLVED: To stabilize the output luminous flux of a semiconductor laser light source at all times, without the effect of returned light by providing a mode- locking means for adjusting the amount of the returned light, which is fed back to the semiconductor laser light source. SOLUTION: A mode-locking control means 14 is arranged in the light path between a polarized beam splitter 20 and aλ/4 plate 24. An angle-adjusting mechanism 30, which reflects a part of the transmitted light that has been transmitted through the polarized beam splitter 20, and adjusts a partial reflecting plate 28 that can transmit the remaining part to the specified angle, with respect to the optical axis, is provided. Then, the spectral distribution waveform of the output luminous flux is being measured by an output light measuring device, and the angle of the partial reflecting plate 28 is adjusted. Then, the single frequency peak appears, corresponding to the change in reflectivity of a resonator, constituted of the partial reflecting plate 28 and a semiconductor laser 16. Even if the amount of the returned light returning to the semiconductor laser 16 is changed by a change in the environment, the frequency of the output luminous flux of the laser light source 2 is maintained at the mode- locked state corresponding to the frequency single frequency peak at all times.
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