The Role of Rayleigh-Wood Anomalies and Surface Plasmons in Optical Enhancement for Nano-Gratings

Abstract

We propose and report on the design of a 1-D metallo-dielectric nano-grating on a GaAs substrate. We numerically study the impact of grating period, slit and wire widths, and irradiating angle of incidence on the optical response. The optimal wire width, w = 160 nm, was chosen based on previous results from investigations into the influence of wire width and nano-slit dimensions on optical and electrical enhancements in metal-semiconductor-metal photodetectors. In this present project, resonant absorption and reflection modes were observed while varying the wire and nano-slit widths to study the unique optical modes generated by Rayleigh-Wood anomalies and surface plasmon polaritons. We observed sharp and diffuse changes in optical response to these anomalies, which may potentially be useful in applications such as photo-sensing and photodetectors. Additionally, we found that varying the slit width produced sharper, more intense anomalies in the optical spectrum than varying the wire width.

Strong Plasmon–Exciton Interactions on Nanoantenna Array–Monolayer WS2 Hybrid System

“…The much higher field enhancement in nanoantenna arrays is attributed to Rayleigh–Wood anomaly arising from the diffraction condition of the pattern. Periodic patterning of dimers into an array reduces the linewidth of the dimers LSP resonance . The anticrossing behavior for isolated square dimers is given in the Supporting Information (Figure S3b), showing narrower Rabi splitting (Ω = 114 meV) compared to that of the square dimer arrays (Ω = 138 meV).…”

“…Periodic patterning of dimers into an array reduces the linewidth of the dimers LSP resonance. [60,61] The anticrossing behavior for isolated square dimers is given in the Supporting Information (Figure S3b), showing narrower Rabi splitting (Ω = 114 meV) compared to that of the square dimer arrays (Ω = 138 meV).…”

Effect of incidence and sidewall taper angles on plasmonic metal–semiconductor–metal photodetector enhancements

“…[22]. The optical enhancement is defined as the maximum ratio of the local enhanced electric field in the substrate, jE local j, to the incident electric field, jE 0 j, all squared-proportional to the irradiance [9]. We applied these equations to calculate the total weighted optical enhancement, G, for the proposed structure illustrated in Fig.…”

“…Depending on the factors mentioned above, Rayleigh-Wood anomalies [9][10][11][12][13][14], Fabry-Perot interference [15,16], surface plasmon polaritons [17,18], nanofocusing [7,8], and impedance matching resonance effects [2,3,[19][20][21] may occur, separately or together, when considering metal-dielectric nanograting structures. Each phenomenon has conditions that may be applied to obtain a resonance, an optimal structure for the promotion of each effect.…”

“…Each phenomenon has conditions that may be applied to obtain a resonance, an optimal structure for the promotion of each effect. For example, Rayleigh-Wood anomalies, which mainly depend on the incident wavelength and periodicity, follow the diffraction grating equation [9]. Moreover, the impedance matching mechanism very weakly depends on the incident wavelength and metallic wire thickness; however, it strongly depends on the incident wave angle [2].…”