All-Dielectric Metasurface Based on Complementary Split-Ring Resonators for Refractive Index Sensing

Mohsen Samadi,José F Algorri,Francesco Dell’Olio,Pablo Roldán-Varona,José M López-Higuera,Fatemeh Abshari,José M Sánchez-Pena,Luis Rodríguez-Cobo,Dimitrios C Zografopoulos

doi:10.3390/photonics9030130

Abstract

Thanks to their lower losses and sharper resonances compared to their metallic counterparts, all-dielectric metasurfaces are attracting a quickly growing research interest. The application of such metasurfaces in the field of refractive index sensing is extremely attractive, especially due to the expected high performance and the simplicity of the sensing element excitation and readout. Herein, we report on an all-dielectric silicon metasurface based on complementary split-ring resonators (CSRRs) optimized for refractive index sensing. A quasi-bound state in the continuum (quasi-BIC) with an ultra-high quality factor can be excited in the near-infrared (NIR) window by violating the structure symmetry. By using the three-dimensional finite element method (3D-FEM), a refractive index sensor for biomedical applications with an ultra-high figure of merit (FoM > 100,000 RIU−1) has been designed, exploiting the quasi-BIC resonance. The proposed design strategy opens new avenues for developing flat biochemical sensors that are accurate and responsive in real time.

Highlights

Resonant micro- and nano-photonic refractive index sensors have long been utilized for real-time, label-free analysis of chemical and biological samples, such as identifying target biomolecules in a biologic fluid or detecting organic liquid compounds
We assume that the metasurface is top illuminated by a sub-pm linewidth laser source operating in the NIR, whose emission frequency can be precisely tuned in a narrow range of a few hundreds of pm by a piezoelectric transducer
We evaluated the effect of a nonzero value of k on the quasi-BIC resonance and the FWHM

Summary

Introduction

Resonant micro- and nano-photonic refractive index sensors have long been utilized for real-time, label-free analysis of chemical and biological samples, such as identifying target biomolecules in a biologic fluid or detecting organic liquid compounds. When target molecules interact with light, the sensor resonance frequency shifts due to light–matter interaction. Surface plasmons [9–12], photonic crystal cavities [3,13–16], and whispering gallery mode resonators [2,4,17–20] have all been used to produce better sensitivities and superior sensing performance. Biochemical sensing applications have used plasmonic nanostructures that support Fano resonances [21–24]. Despite their high sensitivity to the surrounding medium refractive index, they suffer from broad resonances caused by high optical absorption losses in the metal, which severely limit the sensor FoM. Resonances caused by high optical absorption losses in the metal, which severely limit the sensor FoM. IBcayleaxnpdloicthinegmtihcael nsoenns-roards.iative nature of the quasi-BIC mode, exceptionally high-quality factors and FoMs can be produced, allowing for the design of highly accurate biological and chemical sensors Ionf tahseyNmImRewtriyn.dQowua, stih-BeIMC Smsohdoewsshtwavoe malureltaidpyolabrereensoenxapnlcoeitse.dMienanmwahniyle,aapnpaliscyamtiomnetdryominatihnes,stinrucclutudriengofnthoenlsilnoettaerdoCpStiRcRs acannd bsenussiendgt[o36tr–i3g8g]e.r a quasi-BIC with an ultra-high Q-factor thanks to the vanishing radiation lossesInfooruarssmtuadllyd, ebgyreexaomf ainsyinmgmtheetrsye.nQsiutaivsit-yBIoCf mthoedqeusahsai-vBeICalmreaodye btoeetnheexsupploeirtsetdraitne mmaendyiuampprleicfraaticotinvde oinmdaeixn,s,winecalussdeisnsgednothnelinCeSaRr Rop-MticSssaenndsisnegnscianpgac[3it6y–.3B8y]. exploiting the non-Irnadoiuartivsteundayt,ubrye eoxfatmheinqiunagsit-hBeICsemnsoidtiev,iteyxcoefptthioenqaullaysih-BigIhC-qmuoadlietytofatchteorssuapnedrsFtroaMtes mcaendibuemprreofdrauccteivde, ianlldoewxi,nwgefaosrsethsseeddetshiegnCSoRf Rh-iMghSlyseancsciunrgacteapbaicoiltoyg. iBcayleaxnpdloicthinegmtihcael nsoenns-roards.iative nature of the quasi-BIC mode, exceptionally high-quality factors and FoMs can be produced, allowing for the design of highly accurate biological and chemical sensors

Metasurface

Simulation Results

Conclusions