Monolithic Transimpedance Amplifier for On-Chip Light Monitoring in Pure Silicon Photonics

We present a transimpedance amplifier for on-chip optical power monitoring monolithically integrated into a pure Silicon Photonics platform, with no modifications to the fabrication process used by commercial foundries. The designed electronic circuit targets the conversion into voltage signals of the electrical current generated by integrated germanium photodiodes, performed directly on the photonic chip. The amplifier, with a transimpedance gain of 10 kΩ, has been characterized and validated to read light signals up to a frequency of 2 MHz and with an intensity down to about −40 dBm. The circuit is suitable for effectively monitoring the behaviour of photonic devices in a vast range of applications, without penalties in the optical functionality or additional fabrication costs. It thus represents a first demonstration of a more general analog electronics integration into pure Silicon Photonics, paving the way to complex on-chip elaboration and processing towards monolithic electronic control of large-scale optical circuits.