Hollow Plasmonic U‐Cavities with High‐Aspect‐Ratio Nanofins Sustaining Strong Optical Vortices for Light Trapping and Sensing

Abstract

Coupling of ridge hot spots with a scalable resonant U‐cavity fully traps light in intense optical vortices, generating strong and sharp resonances with widths as small as 14 nm. Tunable resonance wavelengths from visible to near‐infrared are achieved by controlling the cavity dimensions. Sensing performance with a figure of merit of 136 is attained and biosensing in a protein‐ligand scheme is demonstrated.

Fano-resonant aluminum and gold nanostructures created with a tunable, up-scalable process

“…10 Fano-resonances occur when a radiative plasmonic mode couples to a non-radiative mode 11 or even two radiative resonances hybridize and form a combination of a superradiant and a subradiant mode. 10,20,21 Most of these structures however are expensive to produce for visible wavelengths on sizable areas, since they require serial patterning such as electron beam writing and ion beam milling 22 . Fano-resonances have been found in many different systems, ranging from split-ring 16,17 or dolmen structures, 18 over few-particle clusters, 19 to gratings.…”

Independent light-trapping cavity for ultra-sensitive plasmonic sensing

“…The fabricated independent-cavity structure achieves high sensitivities and FOM values among those of plasmonic sensors based on nanostructures. [2][3][4][5][6]11,13,14,[21][22][23][24][25][26][27][28][29][30][31] In summary, an independent-cavity structure was fabricated by a simple process and exhibits the sharp reflectance dips that are sensitive to a change in the RI of the surrounding medium. Light was trapped in the optical vortices due to the plasmonic cavity modes without SPR propagation or leakage; therefore, the resonance dips do not depend on the angle of an incident light.…”

“…In this study, an independent cavity structure, which follows Fabry-P erot cavity behavior as previously reported, 14 was fabricated by a simple process. A plasmonic sensor based on this cavity structure achieves high sensitivity with a very narrow full-width-at-half-maximum (FWHM) by trapping light in the cavities without light propagation or leakage due to plasmonic cavity modes.…”

Plasmonic Hybrid Cavity-Channel Structure for Tunable Narrow-Band Optical Absorption

“…The characteristics of surface plasmons, realizing collective electron density oscillations at the interface between metal and dielectric, make it possible for plasmonic structures to support subwavelength modes with tightly confined field enhancement. Designs of various optical devices such as waveguides, sensors, light emitters, as well as filters have been proposed [4][5][6][7][8][9]. Plasmonic structures have been found to excite plasmons both with propagating and localized nature.…”

“…The tunability of the single band is realized by varying the U-cavity width instead of varying the channel width, thus dissociating the control of the resonance wavelength (U-cavity) from the structure used to confine light (channel). The hybrid structure can be fabricated using a similar fabrication method to that described in [9]. The characteristics of the coupling of the channel mode with the horizontal surface plasmon mode of the U-cavity in the hybrid cavity-channel structure offer new ways to design band-stop filters, optical switches, spectrally selective bolometers and spectrometers.…”