Abstract

Frequency upconversion of near-infrared photons to the visible range is strategical for information technology, as it can provide an alternative for the read out of telecom signals using efficient silicon-based detectors. Light upconversion is a nonlinear process mediated by matter that consists in the interaction of either energy-degenerate photons, such as in second-harmonic and third-harmonic generation (THG), or photons with different energies, such as in sum frequency generation (SFG). We recently investigated frequency upconversion in both plasmonic and dielectric nanoantennas [1,2]. Thanks to the adopted dual-beam pump scheme, where an ultrashort pulse (ω) at telecom wavelength (λ = 1551 nm) impinges on the sample along with its frequency-doubled replica (2ω), THG and SFG are degenerate in energy. This, along with coherence, enables the interference between the processes. Yet, we found that in individual nanoantennas symmetry plays a major role in enhancing/suppressing the interference between SFG and THG. By tuning the relative phase between the two impinging pulses, we performed all-optical switching of upconverted light with efficiency > 50% in asymmetric plasmonic antennas [2].

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