| abstract |
(57) [Problem] To provide a wavelength tunable filter having no polarization dependence and a high response speed. SOLUTION: A depletion layer 13 is generated inside an etalon having reflection surfaces 21 and 22 on both sides, and the thickness d of the depletion layer 13 is changed to change the resonance wavelength and selectively emit light of a predetermined wavelength. Through. The depletion layer generating means may be a pn junction composed of p + region 11 and n region 12, An OS structure, a Schottky junction, or the like may be used. |