Non-invasive light observer

Abstract: Photonic technologies lack non-invasive monitoring tools to inspect the light inside optical waveguides. This is one of the main barriers to large scale of integration, even though photonic platforms are potentially ready to host several thousands of elements on a single chip. Here, we demonstrate non-invasive light observation in silicon photonics devices by exploiting photon interaction with intra-gap energy states localized at the waveguide surface. Light intensity is measured through a ContactLess Integrated Photonic Probe (CLIPP) that introduces no measurable extra-photon absorption and a phase perturbation as low as 0.2 mrad, comparable to thermal fluctuations of less than 3 mK. Multipoint light monitoring is demonstrated with a sensitivity of -30 dBm and a dynamic range of 40 dB. CLIPP technology is simple, inherently CMOS compatible, and scalable to hundreds of probing points per chip. This concept provides a viable way to real-time conditioning and feedback control of densely-integrated photonic systems.