Linear phase demodulation using an integrated coherent receiver with an ultra-compact grating beam splitter

In this paper, for the first time, we demonstrate the closed-loop operation of an integrated coherent receiver with the grating-based beam splitter. The drive voltage to the modulator pair is obtained through the integration of the detector current across the capacitance of the detector and the modulator, and hence, the level of this drive voltage is proportional to the detected photocurrent level. When the photocurrent is sufficiently high to provide adequate loop gain, the integrated receiver can closely track signal phase. Consequently, the demodulated signal is very linear.