| 摘要 |
PROBLEM TO BE SOLVED: To actualize large-capacity ultra-high speed information transmission by a multiplexing system and to miniaturize the optical control element for the transmission by integration. SOLUTION: As the optical control element, a composite diffraction grating 1 is used which has both a Bragg reflecting diffraction grating 11 for giving narrow-band wavelength selectivity to the optical control element and a long- cycle diffraction grating 12 inclination at about 45 deg. to an axis of wavelength propagation for performing efficient radiation mode conversion and obtaining emitted light with high radiation directivity. The functions of both the Bragg reflecting diffraction grating and long-cycle diffraction grating 12 completely overlap to efficiently obtain emission spectral diffusion with narrow-band wavelength selectivity and light directivity. The composite diffraction grating 1 has a Bragg reflecting chirp diffraction grating 11 and an about 45 deg.-inclination long-cycle diffraction grating 12 placed over the other at the same place as the optical waveguide and Bragg reflecting diffraction gratings 11 are arranged as reflecting mirrors at both the ends of the 45 deg.-inclination long-cycle diffraction grating 12 to constitute a resonator structure. |
