Differential phase-shift-keying demodulation by coherent perfect absorption in silicon photonics.

We demonstrate a novel differential phase-shift-keying (DPSK) demodulator based on coherent perfect absorption (CPA). Our DPSK demodulator chip device, which incorporates a silicon ring resonator, two bus waveguide inputs, and monolithically integrated detectors, operates passively at a bit rate of 10 Gbps at telecommunication wavelengths, and fits within a mm-scale footprint. Critical coupling is used to achieve efficient CPA by tuning the gap between the ring and bus waveguides. The device has a vertical eye opening of 12.47 mV and a quality factor exceeding 3×10⁴. The fundamental principle behind this photonic circuit can be extended to other formats of integrated demodulators.