| 摘要 |
PURPOSE:To reduce the generation of crosstalk without decreasing diffraction efficiency by using two staircase type diffraction gratings in combination. CONSTITUTION:Light incident at an angle theta to a normal to a reflecting surface is reflected by a plane 51 and projected at the angle theta to the normal to enter the 2nd staircase type diffraction grating 62 in parallel to an axis 41. Light incident from the 1st staircase type diffraction grating 52 at the angle theta to a normal to the reflecting surface, on the other hand, is reflected by a plane 61 and projected at the angle theta to the normal. Then, the incidence directions of the incident light beams, the normals to the reflecting surfaces, and the projection directions of center wavelength light are parallel to ridge lines 53 and 63 and contained in planes perpendicular to the planes 51 and 61, so that the shadows of planes adjoining to the planes 51 and 61, so that the shadows of planes adjoining to the planes 51 and 61 are not formed. A demultiplexer, thereby, reduces crosstalk generated owing to the mixture of light beams having adjacent wavelengths without decreasing the diffraction efficiency of the diffraction gratings. |
