Molecular platform for frequency upconversion at the single-photon level

TL;DR

This paper proposes a nanoscale molecular optomechanical platform capable of upconverting far and mid-infrared photons to visible or near-infrared wavelengths, enabling single-photon detection in previously inaccessible spectral regions.

Contribution

It introduces a novel molecular platform utilizing nanoantennas and vibrational modes for efficient frequency upconversion at the single-photon level, suitable for current technology.

Findings

The scheme can achieve single-photon sensitivity in the IR range.

Optimized platforms can operate with high conversion efficiency.

The approach is feasible with existing nanofabrication techniques.

Abstract

Direct detection of single photons at wavelengths beyond 2 microns under ambient conditions remains an outstanding technological challenge. One promising approach is frequency upconversion into the visible (VIS) or near-infrared (NIR) domain, where single photon detectors are readily available. Here, we propose a nanoscale solution based on a molecular optomechanical platform to up-convert photons from the far and mid-infrared (covering part of the THz gap) into the VIS-NIR domain. We perform a detailed analysis of its outgoing noise spectral density and conversion efficiency with a full quantum model. Our platform consists in doubly resonant nanoantennas focusing both the incoming long-wavelength radiation and the short-wavelength pump laser field into the same active region. There, infrared active vibrational modes are resonantly excited and couple through their Raman polarizability to the pump field. This optomechanical interaction is enhanced by the antenna and leads to the coherent transfer of the incoming low-frequency signal onto the anti-Stokes sideband of the pump laser. Our calculations demonstrate that our scheme is realizable with current technology and that optimized platforms can reach single photon sensitivity in a spectral region where this capability remains unavailable to date.