Optomechanical interactions allow coherent conversion of signals between optical and mechanical domains. Self-assembled metallic nanocavities containing single molecular layers act as mechanical springs/oscillators. Interaction of light and matter in these sub-nm mode volumes allows extreme optomechanical coupling and single mid-infrared (MIR) photon sensitivity. Here we achieve frequency upconversion of MIR incoming photons to visible photons via surface-enhanced Raman spectroscopy in doubly-resonant metasurfaces. Our results on efficient frequency upconversion of infrared radiation in visible regime via molecular optomechanics open new potential in plasmon-based low-cost infrared spectroscopic techniques.
We show strong coupling of a mid-infrared microscale resonator with ultra-localised plasmonic nanocavity modes. This enables new types of mixing between IR absorption and surface-enhanced Raman scattering (SERS), opening up new types of ultrasensitive molecular detection.
Nanoscale localized optical cavities are self-assembled by depositing Au nanoparticles onto few μm metal discs with molecular spacers. Coupling between the microscale resonator and nanocavity in this nanoparticle-on-resonator (NPoR) scheme, reveals extreme near-field enhancements resulting in boosted SERS intensities. We anticipate that such near-field enhancements open new horizons in single-molecule photonic circuits and molecular optomechanics.
KEYWORDS: Signal processing, Terahertz radiation, All optical signal processing, Data processing, Modulation, Metamaterials, Absorption, Picosecond phenomena, Networks, Ultrafast phenomena
Energy-efficient ultrafast all-optical signal processing may contribute to solving growing bandwidth and energy challenges in optical telecommunications. However, conventional solutions for all-optical data processing rely on nonlinear optical materials with inherent minimum power requirements and trade-offs between bandwidth and speed. In contrast, the coherent interaction of light-with-light in an absorber of nanoscale thickness can facilitate high-contrast modulation of one optical signal with another, ultimately with few-femtosecond response times and at arbitrarily low (even single photon) intensities.
We report here on the first demonstration of a fiberized metamaterial device for all-optical signal processing based upon coherent modulation of absorption. The integrated metadevice is based on a plasmonic metamaterial of nanoscale thickness fabricated on the core area of a single-mode optical fibre, and designed to operate over the 1530 – 1565 nm telecoms wavelength range. We demonstrate signal processing operations analogous to logical NOT, XOR and AND functions at effective rates from tens of kbit/s up to 40 Gbit/s with energy consumption as low as 2.5 fJ/bit, as well as selective absorption and transmission of picosecond pulses and the generation of 1 ps ‘dark pulses’. We anticipate that such metadevices, with THz bandwidth, may provide solutions for quantum information networks as well as orders-of-magnitude improvements in speed and energy consumption over existing nonlinear approaches to all-optical signal processing in coherent information networks.
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