| 摘要 |
PURPOSE:To reduce inter-wavelength crosstalk and to shorten coupling length by composing one cycle of a peak part which is a high-refractive-index area of a grating and a bottom part which is a low-refractive-index area, and varying their ratio and length over a coupling area. CONSTITUTION:The grating 8 is formed in the area where propagation modes generated in 1st and 2nd waveguides 4 and 6 are coupled. Then the grating 8 has one cycle composed of the peak part as the high-refractive-index area and the bottom part as the low-refractive-index area, the ratio of the peak part and bottom part to one cycle is distributed in a tapered shape over the coupling area, and the length of one cycle is distributed in a tapered shape over the coupling area. Desired wavelength light is demultiplexed with excellent filter characteristics, and even when the grating depth for shortening the coupling length is increased, the desired wavelength light can be demultiplexed without deteriorating the filter characteristics. Consequently, the inter-wavelength crosstalk is reduced and the coupling length comes to short. |
