| 摘要 |
PROBLEM TO BE SOLVED: To provide a means for regulating wavelengths of a laser in polarizing directions of highest contrast similarly to the case of one wavelength even by a two-wavelength light source. SOLUTION: A light source uses a laser for generating two wavelengths, and a first wavelength plate HWP1 and a second wavelength plate HWP2 are inserted immediately thereafter. At the time of regulating light ofλ1 , first a filter F1 for cutting light ofλ2 and transmitting the light ofλ1 is inserted into an optical path between an interferometer and the source. In addition, the HWP1 is rotated to regulate to an orientation that contrast of interference fringes becomes maximum. Meanwhile, at the time of regulating the light ofλ2 , a filter F2 for cutting the light ofλ1 and transmitting the light ofλ2 is inserted into the path, and the HWP2 is rotated to maximize the contrast of the fringes. A polarization beam splitter PBS used in the interferometer is designed to be sued for two wavelengthsλ1 ,λ2 . 1/4 wavelength plates QWP1 to QWP3 are designed to give a phase difference of 90 deg. with two wavelengths ofλ1 ,λ2 by using two types of anisotropic crystals.
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