| 摘要 |
PURPOSE:To separate effectively a first-order diffracted light as a used modulating light from zero-order diffracted light of the reflected light to prevent the degradation in extinction ratio by changing the optical path of the reflected light in an ultrasonic optical modulator to such direction by an optical path changing member that this optical path is deviated from a reflecting mirror provided in the emitting part of a laser light source. CONSTITUTION:A reflected light B reflected on an AOM 3 is made incident on a peripheral non-lens part 21b of a condenser lens 21. The reflected light B incident on the condenser lens 21 goes toward a laser light source 1 as a light approximately parallel with or coaxial to the reflected light B. Consequently, the reflected light B goes off a reflecting mirror 1s unless the length between the condenser lens 21 and the laser light source 1 is made extremely short. Thus, the reflected light of the reflected light B is not made incident on the AOM 3 again in coaxial relations to the reflected light and a first-order light A1 an the zero-order light of the reflected light made incident on the AOM 3 again do not overlap. That is, the degradation in the extinction ratio is prevented.
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