Silicon-wire-based ultrasmall lattice filters with wide free spectral ranges.

Using silicon-on-insulator-based silicon-wire waveguides with submicrometer cross sections, we constructed ultrasmall channel-dropping lattice filters for 1.5-microm infrared systems. The waveguide's low-loss bends with 2.5-microm radius reduce the total length of the filter to less than 100 microm and enlarge the free spectral range to more than 80 nm. The measured spectra show fine channel-dropping characteristics, and the results agree well with numerical predictions. Moreover, we have succeeded in tuning the dropping wavelength by adjusting the lengths of the delay lines.