| 摘要 |
<p>An array waveguide diffraction waveguide diffraction grating (11) for receiving light beams having different wavelengths from light input waveguides (2), separating the light beams by using the diffraction effect that an array waveguide (40) has, and outputting the separated light beams from respective light output waveguides (6) is formed on a substrate (1) including a platelike member (8a) having a linear expansion coefficient larger than that of the substrate (1) and provided on the back of the substrate (1). Each light beam is transmitted at around the light transmission center wavelength. The light transmission center wavelength is shifted toward the long wavelength side with temperature, and the platelike member (8a) expands more than the substrate (1) does with temperature. As a result, the substrate (1) warps downward, compressive stress is caused in the array waveguide (40), the refractive index of the array waveguide (40) decreases, and each light transmission center wavelength is shifted toward the short wavelength side. The shift toward the short wavelength side offsets the shift toward the long wavelength side due to temperature rise. The variation of each light transmission center wavelength depending on temperature is decreased and limited to a preset wavelength range in a preset temperature range.</p> |
