Silicon optical filters reconfigured from a 16 × 16 Benes switch matrix

Reconfigurable optical filters with tailorable performances are highly demanded in multi-purpose adaptive signal processing applications. We demonstrate infinite impulse response (IIR) silicon optical filters with a variable filter order by switching the optical path in a 16 × 16 Benes switch chip. The basic unit of the optical filter is a dual-ring assisted Mach-Zehnder interferometer. TiN microheaters are integrated in both ring resonators for resonance control, allowing for continuous tuning of the filter center wavelength and the bandwidth. Multiple high-order optical filters from the 2^nd order up to the 14^th order are obtained. The filter bandwidth tuning range is from 0.19 nm (23.75 GHz) to 1.06 nm (132.5 GHz) with a 1-dB in-band ripple. The out-of-band rejection ratio exceeds 30 dB for the 8^th and 10^th-order filters, limited by the inter-path optical crosstalk in the Benes architecture. The results point to new ways of reutilizing an existing switch matrix to flexibly construct wavelength-filtering devices.