Detecting mid-infrared light by molecular frequency upconversion in dual-wavelength nanoantennas.

Xomalis, Angelos; Zheng, Xuezhi; Chikkaraddy, Rohit; Koczor-Benda, Zsuzsanna; Miele, Ermanno; Rosta, Edina; Vandenbosch, Guy A E; Martínez, Alejandro et al. · Science · 2021

basic_science · Level V

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Abstract

Coherent interconversion of signals between optical and mechanical domains is enabled by optomechanical interactions. Extreme light-matter coupling produced by confining light to nanoscale mode volumes can then access single mid-infrared (MIR) photon sensitivity. Here, we used the infrared absorption and Raman activity of molecular vibrations in plasmonic nanocavities to demonstrate frequency upconversion. We converted approximately 10-micrometer-wavelength incoming light to visible light by surface-enhanced Raman scattering (SERS) in doubly resonant antennas that enhanced upconversion by more than 10<sup>10</sup>. We showed 140% amplification of the SERS anti-Stokes emission when an MIR pump was tuned to a molecular vibrational frequency, obtaining lowest detectable powers of 1 to 10 microwatts per square micrometer at room temperature. These results have potential for low-cost and large-scale infrared detectors and spectroscopic techniques.