Coherent Control of a Plasmonic Nanoantenna Integrated on a Silicon Chip

Abstract

Illuminating a plasmonic nanoantenna by a set of coherent light beams should tremendously modify its scattering, absorption and polarization properties, thus enabling all-optical dynamic manipulation. However, diffraction inherently makes coherent control of isolated subwavelength-sized nanoantennas highly challenging when illuminated from free-space. Here, we overcome this limitation by placing the nanoantenna at a subwavelength distance of the output facet of silicon waveguides that provide monolithically-defined paths for multibeam coherent illumination. Inspired by coherent perfect absorption (CPA) concepts, we demonstrate experimentally modulation of the nanoantenna scattering by more than one order of magnitude and of the on-chip transmission by >50% over a ~200 nm bandwidth at telecom wavelengths by changing the phase between two counter-directional coherent guided beams. Moreover, we demonstrate coherent synthesis of polarization of the radiated field by illuminating the nanoantenna from orthogonal waveguides. Our finding paves the way towards coherent manipulation of nanoantennas and all-optical processing without nonlinearities in an integrated platform.

Toward Chiral Sensing and Spectroscopy Enabled by All‐Dielectric Integrated Photonic Waveguides

“…This is quite striking since the fields in the evanescent region are much weaker than in the gap spacing two waveguides, wherein they are essentially similar to those in the waveguide core. [77,78] Yet, this configuration still retain common features with respect to the previous case, in particular, the peak position (or resonance frequency) dependent on the helix radius, and the intermodal conversion between L-and R-CPGM, and vice versa, as a result of the interaction between the CPGMs and the chiral structure (Figure 4b).…”

“…Then, using an end-fire coupling setup, the light exiting the input waveguide will excite the chiral structure in the near-field, here acting as a probe. The output waveguide will collect the light both scattered by the structure and transmitted from waveguide to waveguide, [77,78] thus enabling the read-out of the chiroptical interaction. To account for the chiral spectral response, we first represent the transmission and mode conversion spectra for L-and R-CPGM (Figure 3b).…”

Double metal layer lift-off process for the robust fabrication of plasmonic nano-antenna arrays on dielectric substrates using e-beam lithography

“…The intense near-field in such regions can be used to boost the weak intensity of signals generated by the analytes of interest, such as Raman scattering in SERS. Plasmonic nano-antennas can be integrated onto optical waveguides, leading to the realization of integrated plasmonic sensors, which combine the signal enhancement of the plasmonic structures with the miniaturization, scaling and interfacing provided by the integrated waveguides [6][7][8][9][10][11][12]. Given the subwavelength dimensions of plasmonic nano-antennas and considering the inverse relationship between the Raman scattering cross-section and wavelength used, 785 nm is one the most used wavelengths to perform this technique since it offers a compromise between performance and technological requirements.…”

Combination of nanophotonic biosensors and light-assisted immobilization procedures for the detection of cardiac biomarkers

“…Given the importance of the evanescent field profile over the sensing performance, the near-field behavior of the PBG sensing structures has been studied using SNOM technology, which has been used in previous works to characterize SOI structures as nanoatennas Espinosa-Soria et al, 2018). SNOM measurements were performed with a tailored MultiView 4000 system (Nanonics Imaging Ltd.) working in collection mode as schematized below (see figure 4.2).…”

“…To this aim, FDTD simulations were done using CST Microwave Studio, which is specially created to solve electromagnetic problems in three dimensions where the working frequencies are high, as it is the case that concerns us. For our simulations, a 61 period PBG structure has been considered, such as for the one manufactured (Espinosa-Soria et al, 2018). To perform the system of equations that the simulation resolves, a hexahedral type mesh has been performed with 1.34 million cells, with at least 4 divisions per wavelength.…”