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.
Carminati, M., Grillanda, S., Ciccarella, P., Morichetti, F., Bellotti, G., Bianchi, D., … Sampietro, M. (2014). Impedance-based transparent monitoring of light for local control of integrated photonic circuits. In Procedia Engineering (Vol. 87, pp. 1545–1548). Elsevier Ltd. https://doi.org/10.1016/j.proeng.2014.11.594