Optically reconfigurable quasi-phase-matching in silicon nitride microresonators

Abstract

Bringing efficient second-order nonlinear effects in integrated photonics is an important task motivated by the prospect of enabling all possible optical functionalities on chip. Such task has proved particularly challenging in silicon photonics, as materials best suited for photonic integration lack second-order susceptibility (χ (2) ). Methods for inducing effective χ (2) in such materials have recently opened new opportunities. Here, we present optically reconfigurable quasiphase-matching in large radius Si 3 N 4 microresonators resulting in mW level on-chip secondharmonic generated powers. Most importantly we show that such all-optical poling can occur unconstrained from intermodal phase-matching, leading to widely tunable second-harmonic generation. We confirm the phenomenon by twophoton imaging of the inscribed χ (2) grating structures within the microresonators as well as by dynamic tracking of both the pump and secondharmonic mode resonances. These results unambiguously establish that the photogalvanic effect, responsible for all-optical poling, can overcome phase mismatch constraints even in resonant systems, and simultaneously allow for the combined record of output power and tunability.

Near perfect two-photon interference out a down-converter on a silicon photonic chip

“…In contrast, 𝜒 (2) materials represent a viable alternative by leveraging spontaneous parametric down-conversion (SPDC) and thus relaxing the stringent condition for on-chip filtering as the generated photon pairs are spectrally far separated from the pump. Previous works have already shown the possibility of enabling an efficient 𝜒 (2) response in a 𝜒 (3) Si substrate providing new grounds for exploiting SPDC on this platform [13][14][15][16][17]. All these works have reported only either technological or non-linear characterizations.…”