| 摘要 |
PURPOSE:To obtain an optical waveguide type wavelength filter by giving the difference between the refractive index of a guide part or core part and the refractive index of a clad part dispersion to light wavelength, and using a material which inverts the sign of the difference in refractive index between the low-wavelength and high-wavelength sides of certain wavelength. CONSTITUTION:When the refractive index of a guide part which constitutes an optical waveguide is denoted as n1 and the refractive index of the clad part is denoted as n2, the sign of the difference delta=(n1-n2) in refractive index between the guide part and clad part is inverted between the short-wavelength and long-wavelength sides of certain desired wavelength. In a wavelength range of n1>n2, light is confined to the guide part to enter a waveguide mode and in a wavelength range of n1<=n2, on the other hand, light at the guide part decreases in intensity gradually as it is propagated to enter a radiation mode and then leaks from a boundary surface. For the purpose, the wavelength range of n1>n2 is set on the short-wavelength side to obtain a low-pass wavelength filter and the wavelength range of n1>n2 is set on the long-wavelength side to obtain a high-pass wavelength filter. |
