Experimental demonstration of surface and bulk plasmon polaritons in hypergratings

Abstract

Hyperbolic metamaterials (HMMs) represent a novel class of fascinating anisotropic plasmonic materials, supporting highly confined bulk plasmon polaritons in addition to the surface plasmon polaritons. However, it is very challenging to tailor and excite those modes at optical frequencies using prism coupling technique because of the intrinsic difficulties to engineer non-traditional optical properties using artificial nanostructures and the unavailability of high refractive index prisms for matching the momentum between the incident light and the guided modes. Here, we experimentally demonstrate the excitation of both surface and bulk plasmon polaritons in a HMM through a grating coupling technique of surface plasmon excitation that makes use a hypergrating, which is a combined structure of metallic diffraction grating and HMM. Initially, we propose an optical hyperbolic metamaterial based on Au/TiO2 multilayers and confirm the hyperbolic dispersion, and the presence of high-k modes in the fabricated HMM. Reflection measurements as a function of incident angle and excitation wavelength show the existence of both surface and bulk plasmon polaritons inside the hypergrating. The proposed configuration is expected to find potential applications in bio-chemical sensors, integrated optics and optical sub-wavelength imaging.

Hyperbolic metamaterials-based plasmonic biosensor for fluid biopsy with single molecule sensitivity

“…Such BPPs support extremely high momentum and have been shown experimentally to be extremely sensitive to any change in the dielectric constant within the range of its evanescently decaying field in the superstrate. We have demonstrated the excitation of these high-k modes by a grating coupling method [17][18][19]. However, as we show in the following sections, grating coupling did not affect the high sensitivity of the HMM biosensor.…”

“…Since the bulk plasmon modes represent the entire family of gap plasmon modes of a multilayer, large modal indices are possible. This corresponds to strong mode confinement and shorter propagation length, which in turn provide high quality (Q) factor modes [17]. We studied the properties of BPP modes by recording the reflectance spectra as a function of excitation wavelength at a particular incident angle (Figure 3b).…”

Hyperbolic Metamaterials: Design, Fabrication, and Applications of Ultra-Anisotropic Nanomaterials

“…12.4a. Since both surface and bulk plasmon mode excitation depends on incident angle, we have measured the reflectance of GCAHM for different angles of incidence [17]. We have observed a blue shift in reflectance minima for both surface and bulk plasmon modes as the incident angle increases.…”

“…In this context, we have proposed a novel hypergrating configuration [17] to design optical HMMs and experimentally demonstrate that it is possible to excite SPP and BPP modes at optical frequencies using a grating coupling technique based on surface plasmon excitation. Nanofabrication and nanophotonics strongly interplayed during the design and fabrication processes to create the artificial metal-dielectric superlattice with subwavelength layer thickness (almost λ/20), and to implement a proper grating to couple and simultaneously probe SPP and BPP modes.…”

All-optical switching in silicon photonic waveguides with an epsilon-near-zero resonant cavity [Invited]

“…In order to further reduce losses associated with the use of metals and subsequently reduce switching energy requirements and modulation efficiency, the reduction of the number of metallic meta-atoms [33] in a metamaterial modulator is desirable. This, however, needs to be achieved while preserving the conditions required for efficient modulation.…”