A low-noise resonant input transimpedance amplified photodetector

TL;DR

This paper introduces a resonant input transimpedance amplified photodetector operating at 90 MHz with near-theoretical low noise, enabling shot-noise limited detection at low input powers for applications requiring high sensitivity.

Contribution

The design employs a low-noise, common-source JFET amplifier to achieve near-theoretical noise performance in a resonant photodetector at 90 MHz.

Findings

Input current noise of 1.2 pA/√Hz, close to the 1.0 pA/√Hz theoretical limit.

Shot-noise limited operation for input powers above 14 μW at 461 nm.

Achieves a noise equivalent power of 3.5 pW/√Hz.

Abstract

We present the design and characterisation of a low-noise, resonant input transimpedance amplified photodetector. The device operates at a resonance frequency of $90 \,\textrm{MHz}$ and exhibits an input referred current noise of $1.2\,\textrm{pA}/\sqrt{\textrm{Hz}}$---marginally above the the theoretical limit of $1.0\,\textrm{pA}/\sqrt{\textrm{Hz}}$ set by the room temperature Johnson noise of the detector's $16\,\textrm{k}\Omega$ transimpedance. As a result, the photodetector allows for shot-noise limited operation for input powers exceeding $14\,\mu\textrm{W}$ at $461\,\textrm{nm}$ corresponding to a noise equivalent power of $3.5\,\textrm{pW}/\sqrt{\textrm{Hz}}$. The key design feature which enables this performance is a low-noise, common-source JFET amplifier at the input which helps to reduce the input referred noise contribution of the following amplification stages.