Molecular optomechanical frequency upconversion at the single-photon level

Abstract

Direct detection of single photons at wavelengths beyond 2 microns under ambient conditions remains an outstanding technological challenge. One promising solution 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 THz and mid-infrared (MIR) photons into the VIS-NIR domain, and perform a detailed analysis of its added noise and conversion efficiency with a full quantum model. Our platform consists in doubly resonant nano-antennas 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, at wavelengths reaching into the THz domain, with an added noise only limited by the thermal occupancy of the molecular vibration.

Optomechanical Collective Effects in Surface-Enhanced Raman Scattering from Many Molecules

“…For example, it has been pointed out theoretically 39 that the presence of many molecules can facilitate reaching the parametric instability at lower laser intensity. The collective response has also been invoked in the design of a photon up-conversion device based on SERS 46 and to explain a recent experiment 47 that reveals a non-linear dependence of the Stokes SERS signal on the pulsed laser intensity. In other related contexts, collective in-arXiv:2001.01750v1 [physics.optics] 6 Jan 2020 teractions have been studied in Raman experiments with exquisitely controlled atoms at ultra-low temperatures and are now applied routinely to study a variety of interesting phenomena, such as superradiant Raman lasing 48 , spin-squeezing 49 and quantum phase transitions 50 .…”