Influence of Vacuum modes on Photodetection

TL;DR

This paper investigates how vacuum modes influence photodetector efficiency and noise, revealing their significant role in quantum efficiency and shot noise, especially under Purcell enhancement conditions.

Contribution

It introduces a theoretical framework accounting for vacuum mode interactions in photodetection, which are usually neglected, affecting efficiency and noise characteristics.

Findings

Vacuum modes contribute to quantum efficiency.

Interaction with vacuum modes affects shot noise.

Design principles for sensitive detectors based on vacuum mode properties.

Abstract

Photodetection is a process in which an incident field induces a polarization current in the detector. The interaction of the field with this induced current excites an electron in the detector from a localized bound state to a state in which the electron freely propagates and can be classically amplified and detected. The induced current can interact not only with the applied field, but also with all of the initially unpopulated vacuum modes. This interaction with the vacuum modes is assumed to be small and is neglected in conventional photodetection theory. We show that this interaction contributes to the quantum efficiency of the detector. We also show that in the Purcell enhancement regime, shot noise in the photocurrent depends on the bandwidth of the the vacuum modes interacting with the detector. Our theory allows design of sensitive detectors to probe the properties of the vacuum modes.