Design and characterization of current-assisted photonic demodulators in 0.18-um CMOS technology

We report on the design of a Current-Assisted Photonic Demodulator (CAPD) using a standard 0.18-um CMOS technology, and its electro-optical characterization. The device can perform both light detection and demodulation in the charge domain, owing to a drift field generated in the silicon substrate by a majority carrier flow. Minimum-size, 10×10 um2 CAPDs exhibit a DC charge-transfer efficiency larger than 80% (corresponding to a demodulation contrast larger than 40% under sine-wave modulation) at the modest power consumption of 10 uW, and a 3-dB bandwidth > 45 MHz. An excellentlinearity with an error lower than 0.11% is obtained in phasemeasurements. CAPDs with optimized modulation-electrode geometries are finally designed, aiming at improved contrast-vs-power trade-off.