Strong coupling between quasi-bound states in the continuum and molecular vibrations in the mid-infrared

Abstract

Strong light–matter coupling is of much interest for both fundamental research and technological applications. The recently studied bound state in the continuum (BIC) phenomenon in photonics with controlled radiation loss rate significantly facilitates the realization of the strong coupling effect. In this work, we report the experimental observation of room temperature strong coupling between quasi-BIC resonances supported by a zigzag metasurface array of germanium elliptical disks and the vibrational resonance of polymethyl methacrylate (PMMA) molecules in the mid-infrared. Based on the approach of tuning the quasi-BIC resonance by changing the thickness of the coated PMMA layer, we can easily observe the strong coupling phenomenon, manifested by significant spectral splitting and typical anti-crossing behaviors in the transmission spectrum, with the spectral distance between the two hybrid photon-vibration resonances significantly larger than the bandwidth of both the quasi-BIC resonance and the PMMA absorption line. Our results demonstrate that the use of quasi-BIC resonance in all-dielectric nanostructures provides an effective and convenient approach for the realization of strong coupling effect.

High-Sensitivity Optical Sensors Empowered by Quasi-Bound States in the Continuum in a Hybrid Metal–Dielectric Metasurface

“…It is noted that an ultrahigh Q factor of 412 has been experimentally achieved by the d-qBIC mode. To the best of our knowledge, experimental Q factors achieved by qBICs in plasmonic/hybrid systems are mostly lower than this value. − ,,,,, It is even comparable with some dielectric works. ,,− …”

A High-Sensitivity Refractive Index Sensor with Period-Doubling Plasmonic Metasurfaces to Engineer the Radiation Losses

“…It shows that the electric field is concentrated to both ends of the long axis of the elliptical disks and the QGM can be excited by the x-polarized plane wave, which is similar to the effect of QBIC in the all-dielectric zigzag array. 23 In addition, as α increases, the resonance peak experiences a slight blue shift from 1386 to 1377 nm. This is attributed to a change of the effective index of the QGMs in the zigzag array at a higher perturbation.…”

“…The inset in Figure b illustrates the electric field distribution at the resonance wavelength for the case of α = 10°. It shows that the electric field is concentrated to both ends of the long axis of the elliptical disks and the QGM can be excited by the x -polarized plane wave, which is similar to the effect of QBIC in the all-dielectric zigzag array . In addition, as α increases, the resonance peak experiences a slight blue shift from 1386 to 1377 nm.…”

Multi‐Band Polarization‐Independent Quasi‐Bound States in the Continuum Based on Tetramer‐Based Metasurfaces and Their Potential Application in Terahertz Microfluidic Biosensing

“…[ 38,39 ] As shown in Figure 8b,e,h, for mode 2, in addition to local enhanced electric field around the Cu particles, there is also obvious electric‐field distribution in the PET dielectric layer (the region between the white solid lines and the red dotted line), which corresponds to a waveguide mode. Therefore, mode 2 is actually a hybrid mode induced by the hybridization effect between the LSPR mode and the waveguide mode, [ 46–48 ] which results in the unusual phenomenon of the resonance mode 2 in the transmittance spectrum, as described in Section 4.2. While for mode 3, as shown in Figure 8c,f,i, it is generated by a propagating surface plasmon resonance (SPPR), [ 49,50 ] and Figure 8i clearly indicates the surface wave propagating along the x direction.…”