Plasmon-Enhanced Second Harmonic Sensing

Abstract

It has been recently suggested that the nonlinear optical processes in plasmonic nanoantennas allow for a substantial boost in the sensitivity of plasmonic sensing platforms. Here we present a sensing device based on an array of non-centrosymmetric plasmonic nanoantennas featuring enhanced second harmonic generation (SHG) integrated in a microfluidic chip. We evaluate its sensitivity both in the linear and nonlinear regime using a figure of merit (FOM = Δ � Δ ) that accounts for the relative change in the measured intensity, I, against the variation of the environmental refractive index n. While the signal-to-noise ratio achieved in both regimes allows the detection of a minimum refractive index variation Δ ~ 10 −3 , the platform operation in the nonlinear regime features a sensitivity (i.e. the FOM) that is at least 3 times higher than the linear one. Thanks to the surface sensitivity of plasmon-enhanced SHG, our results show that the development of such SHG sensing platforms with sensitivity performances exceeding those of their linear counterparts is within reach.

Harmonic generation at the nanoscale

“…Extended to the THz spectral region, the concept of nonlinear metasurfaces would allow to enrich the palette of sensors and coherent sources that are now available [Lee et al (2014)]. Finally, the enhanced nonlinear properties in metasurfaces could be exploited to further enhance the performances of sensing platforms with respect to those of simple dense arrays of nonlinear particles [Mesch et al (2016), Ghirardini et al (2018)], as we will describe in the next section.…”

Multiorder Nonlinear Mixing in Metal Oxide Nanoparticles

“…We have also demonstrated that the response is conserved when the particles are embedded in biological media and the excitation beams are raster-scanned, two aspects essential for developing diagnostics and sensing schemes taking full advantage of the nonlinear sensitivity of the optical read-out. 44,45 Schanne-Klein, M.-C.; Beaurepaire, E. Imaging lipid bodies in cells and tissues using third-harmonic generation microscopy. Nature methods 2006, 3, 47-53.…”

Lithium niobate particles with a tunable diameter and porosity for optical second harmonic generation

“…[31][32][33][34] This decrease in the intensity of the SHG response reduces the interest in developing these particles for biological applications (e.g., bioimaging). 35,36 The SHG response of NLO particles can be signicantly enhanced by employing various strategies. 37 These approaches include the preparation of hybrid structures of the NLO material paired with plasmonic metals or organic molecules.…”

“…, bioimaging). 35,36 The SHG response of NLO particles can be significantly enhanced by employing various strategies. 37 These approaches include the preparation of hybrid structures of the NLO material paired with plasmonic metals or organic molecules.…”