Impedance-based transparent monitoring of light for local control of integrated photonic circuits

Abstract

A non-invasive technique is presented for tracking the intensity of light propagating in Si waveguides whose conductivity, increasing due to surface defects-mediated sub-bandgap photon absorption, is monitored through a ContactLess Integrated Photonic Probe (CLIPP). A dynamic range of 40 dB is demonstrated, with a minimum detection level of -30 dBm (local optical power), without perturbing light propagation. A custom-designed multichannel and low-noise integrated front-end allows miniaturized and high resolution sensing (2 pS noise floor), thanks to a significant parasitics reduction. Beyond power monitoring, this novel technique is suitable for tuning and control of key optical devices such as ring resonators.