Integrated SOI High-Order Phase-Shifted Bragg Grating for Microwave Photonics Signal Processing

An integrated high-order phase-shifted Bragg grating, comprising six quarter-wave sections between Bragg grating mirrors in a laterally-corrugated strip waveguide has been realized in silicon-on-insulator technology. A box-like transmission window is created within the 10-nm-wide grating reflection band, realizing a sharp bandpass optical filter with out-of-band rejection exceeding 40 dB and a steep roll-off of ∼300 dB/nm in the transition band. The sharp optical filter has been experimentally tested in microwave photonics (MWP) signal processing applications, namely spectral separation of an optical sideband comprising 1.25 Gb/s data from a 15-GHz-spaced carrier, and sideband suppression for dispersion compensation in a radio-over-fiber link. The results of the characterizations indicate negligible power penalty in terms of bit-error rate for the sideband separation and robust mitigation of dispersion-induced transmission impairment. The device has an ultrasmall footprint of ∼450 × 0.5 μm2, and can be monolithically integrated with germanium photodiodes or silicon modulators as well as other passive subsystems to implement advanced on-chip MWP signal processing functionalities