Ultrahigh-sensitivity optical power monitor for Si photonic circuits

Abstract

A phototransistor is a promising candidate as an optical power monitor in Si photonic circuits since the internal gain of photocurrent enables high sensitivity. However, state-of-the-art waveguide-coupled phototransistors suffer from a responsivity of lower than $10^3$ A/W, which is insufficient for detecting very low power light. Here, we present a waveguide-coupled phototransistor consisting of an InGaAs ultrathin channel on a Si waveguide working as a gate electrode to increase the responsivity. The Si waveguide gate underneath the InGaAs ultrathin channel enables the effective control of transistor current without optical absorption by the gate metal. As a result, our phototransistor achieved the highest responsivity of approximately $10^6$ A/W among the waveguide-coupled phototransistors, allowing us to detect light of 621 fW propagating in the Si waveguide. The high responsivity and the reasonable response time of approximately 100 $\mu$s make our phototransistor promising as an effective optical power monitor in Si photonics circuits.

References in corpus (4)

• Photonics for artificial intelligence and neuromorphic computing
• Waveguide-integrated black phosphorus photodetector with high responsivity and low dark current
• Quantum circuits with many photons on a programmable nanophotonic chip
• Heavy and light hole minority carrier transport properties in low-doped n-InGaAs lattice matched to InP

Cited by in corpus (1)

• Si-waveguide-based optical power monitoring of 2$\times$2 Mach$\unicode{x2013}$Zehnder interferometer based on InGaAsP/Si hybrid MOS optical phase shifter