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

ANGELOS XOMALISHTTPS://ORCID.ORG/0000-0001-8406-9571XUEZHI ZHENGROHIT CHIKKARADDYHTTPS://ORCID.ORG/0000-0002-3840-4188ZSUZSANNA KOCZOR-BENDAHTTPS://ORCID.ORG/0000-0002-6714-0337ERMANNO MIELEHTTPS://ORCID.ORG/0000-0001-5085-9815EDINA ROSTAGUY A. E. VANDENBOSCHALEJANDRO MARTÍNEZHTTPS://ORCID.ORG/0000-0001-5448-0140AND JEREMY J. BAUMBERGHTTPS://ORCID.ORG/0000-0002-9606-9488Authors Info & AffiliationsSCIENCE•2 Dec 2021•Vol 374, Issue 6572•pp. 1268-1271•DOI: 10.1126/science.abk2593GET ACCESS

Optomechanical upconversion

Molecules have rich signatures in their spectra at infrared wavelengths and are typically accessed with dedicated spectroscopic instrumentation. Chen et al. and Xomalis et al. report optomechanical frequency upconversion from the mid-infrared to the visible domain using molecular vibrations coupled to a plasmonic nanocavity at ambient conditions (see the Perspective by Gordon). Using different nanoantenna designs, one with a nanoparticle-on-resonator and the other with nanoparticle-in-groove, both approaches show the ability to upconvert the mid-infrared vibrations of the molecules in the nanocavity to visible light wavelengths. The effect could be used to simplify infrared spectroscopy, possibly with single-molecule sensitivity. —ISO


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 1010. 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.

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