| 摘要 |
<P>PROBLEM TO BE SOLVED: To improve transmission characteristics by suppressing excess loss. Ž<P>SOLUTION: A lens 11a condenses input light and generates a collected beam. A VIPA plate 12 is provided with a reflecting surface 12a highly reflecting light, and a transmissive surface 12b, vapor-deposited with a reflective film 1-1 having a reflectivity lower than that of the reflective surface 12a. In the internal region held in place by the reflecting surface 12a and the transmissive surface 12b, a condensing beam made incident from window 12c is allowed to undergo multiple reflections, and the diffracted light is emitted via the transmissive surface 12b. A reflecting mirror 13 reflects the outgoing light emitted from the transmissive surface 12b, generates the return light and makes the light arrive again at the transmissive surface 12b. The reflecting film 1-1 includes the high-reflectivity film 1a of high reflectivity and the low reflective film 1b of low reflectivity. The high reflecting film 1a is vapor-deposited on the portion of the transmissive surface 12b released with the exit light is of high light intensity, such that the coupling portion of the exit light and the return light is made greater, and the low reflective film 1b is vapor deposited on the portion of the transmissive surface 12b. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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