Plasmonic Perfect Absorber for Refractive Index Sensing and SERS

Abstract

A plasmonic perfect absorber is modeled, and its absorption/reflection properties are investigated in the visible frequency regime using finite-difference time-domain numerical simulation to show how refractive index can be measured accurately using dual interrogation technique (wavelength and intensity interrogations). Very high absorption (>95 %) is observed in the spectral range below 625 nm. The reflection and absorption spectra show a crossover (at 50 %) in which red shifts depend upon the refractive index of the surrounding medium existing on the top of the structured surface. An equivalent of 530 nm red shift of the crossover point per refractive index unit (RIU) is calculated, which is a clear indication that the structure is suitable for refractive index sensing application. The spectral absorption and reflection are polarization insensitive and show perfect absorption (∼90 %) below 550 nm over a wide range of angle of incidence. The structure is proposed to be good for surface-enhanced Raman scattering (SERS) due to high near-field caused by perfect absorption.

Highly Flexible and Voltage Based Wavelength Tunable Biosensor

“…This dielectric loss is the result of the coupling of a part of light to the substrate (bottom metallic layer) through LSPRs. The thickness of the bottom metallic layer is larger than the penetration depth of the incident light and also possesses high losses, and thus eliminates the transmission . The cavity confines the residual of the incident light to maximize the absorption at resonant wavelengths.…”

“…In literature, different groups have calculated high sensitivities in perfect absorbers. Mandal et al, reported 530 nm per refractive index unit (RIU), Yong et al 885 nm RIU −1 , and Cheng et al 1445 nm RIU −1 . Luigi et al reported 0.25 nm V −1 for narrowband optical filter .…”

Narrowband and flexible perfect absorber based on a thin-film nano-resonator incorporating a dielectric overlay

“…Perfect absorbers, which absorb a specific spectral band and do not permit reflection or transmission, have recently gained considerable interest by virtue of their wide range of applications spanning photovoltaic cells 16 , photodetectors 17,18 , thermal imaging 19 , and sensors [20][21][22][23][24][25][26][27][28] . Perfect absorbers engaging various nanostructures (e.g., plasmonic and metasurface schemes) [18][19][20][21][22][23][24][25][26][27]29 and multilayered structures [1][2][3][4]28,[30][31][32][33][34][35][36][37] are being extensively studied. Although narrowband absorbers are known to be suitable for sensing and absorption filtering 2,[25][26][27] , conventional approaches have mostly focused on multiband 21,25 or broadband absorption [31][32][33]…”

Perfect Absorption and Refractive-Index Sensing by Metasurfaces Composed of Cross-Shaped Hole Arrays in Metal Substrate

“…Recently, there is increasing interesting in studying the perfect absorption of electromagnetic waves for refractive-index sensing by employing metasurfaces , metallic nanostructures , and graphene nanostructures [62][63][64][65][66][67][68][69][70][71], in violet [62], visible [1][2][3][4][5][33][34][35][36][37][38][39][40][41][42][43]63,64], infrared [6][7][8][9][10][11][12][13][14][15][16][17][44][45][46][47][48][49][50][51][52]…”

“…Recently, there is increasing interesting in studying the perfect absorption of electromagnetic waves for refractive-index sensing by employing metasurfaces [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ], metallic nanostructures [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , …”