Amorphous-silicon visible-light detector integrated in silicon nitride waveguides

TL;DR

This paper demonstrates an integrated visible-light detector using amorphous silicon on silicon nitride waveguides, enabling high-sensitivity on-chip monitoring for photonic circuits in the visible spectrum.

Contribution

It introduces a compact in-line power monitor with amorphous silicon coating for silicon nitride waveguides operating at 660 nm, with notable responsivity and fast response.

Findings

Responsivity of 30 mA/W achieved

Sensitivity of -45 dBm demonstrated

Sub-microsecond response time recorded

Abstract

Visible light integrated photonics is emerging as a promising technology for the realization of optical devices for applications in sensing, quantum information and communications, imaging and displays. Among the existing photonic platforms, high-index contrast silicon nitride ($Si_{3}N_{4}$) waveguides offer broadband transparency in the visible spectral range and a high scale of integration. As far as the complexity of photonic integrated circuits (PICs) increases, on-chip detectors are required to monitor their working point for reconfiguration and stabilization operations. In this work we present a compact in-line power monitor integrated in $Si_{3}N_{4}$ waveguides that operates in the red-light wavelength range (660 nm). The proposed device exploits the photoconductivity of a hydrogenated amorphous silicon (a-Si:H) film employed as a coating layer of the optical waveguide. Experimental results show a responsivity of 30 mA/W, a sensitivity of -45 dBm and a sub-${\mu}$s time response. These features enable the use of the proposed photoconductor for high-sensitivity monitoring and control of visible-light $Si_{3}N_{4}$ PICs.