All‐Dielectric Active Terahertz Photonics Driven by Bound States in the Continuum

Abstract

This approach became essential for constructing negative index media, which laid a strong foundation for the burgeoning field of metamaterial photonics. Split-ring resonators as the basic building blocks of metamaterials were first proposed to be made up of metallic inclusions at the microwave frequencies. [9] However, beyond the microwave frequencies, metals show considerable Ohmic loss, which created the need for all-dielectric resonator platform with the promise to offer low-loss meta-optics and photonics. The last few years have witnessed an unprecedented use of dielectrics in optical metamaterials based on high-index dielectric materials that have strongly emerged as an alternative approach to disrupt the lossy metalbased subwavelength photonics. [10][11][12][13][14][15][16][17][18] Several interesting phenomena of metamaterials are driven by strong resonances, and their quality (Q) factors become an extremely important parameter that determines the strength of light-matter interaction. The structures with high Q factors offer a new route for strong localization of electromagnetic energy in near fields that allow ultrasensitive sensors and other optical devices. [19][20][21][22][23] Recent trends in this field are based on so-called bound statesThe authors declare no conflict of interest. Keywordsall-dielectric metasurface, bound states in the continuum, optically active metadevices, terahertz, ultrafast switching

Spectral and temporal evidence of robust photonic bound states in the continuum on terahertz metasurfaces

“…An approach to trap light in such remarkable electromagnetic modes is to exploit metasurfaces [2][3][4][5][6][7][8][9], i.e., subwavelength arrays (in the nondiffractive region) where only the specular reflection/transmission channels are allowed by symmetry, wherein outgoing specular channels can be suppressed by tuning the parameters of the system in various manners, leading to symmetry-protected BICs. Achieving robust BICs and quasi-BICs will be of great interest for the realization of cavities with arbitrarily high Q-factor and for applications such as lasing and sensing [10][11][12]. Nonetheless, there are no fundamental works describing how to achieve robust BICs on a general basis, except for well-known symmetry-protected and accidental degeneracies appearing in photonic crystals [3] and asymmetric metasurfaces [7].…”

Lattice‐Enhanced Fano Resonances from Bound States in the Continuum Metasurfaces

“…Recently, Fano resonances of metasurfaces have been linked to bound states in continuum (BIC), which is a field of growing interest. BICs are bound eigenmodes that lie above the photonics light line . This itself is a unique counterintuitive characteristic and because of this, they possess infinite lifetimes and zero‐linewidth resonances under ideal conditions .…”

Guided‐Mode Resonances in All‐Dielectric Terahertz Metasurfaces

“…The simulated results for silicon cuboid resonators with L = 270 µm, W = 180 µm at varying θ are shown in Figure 2a, and L = 270 µm, W = 210 µm are shown in Figure 2b, respectively. [35] The scanning electron microscope (SEM) images of the fabricated sample are shown in Figure 1a The transmission spectra of the all-dielectric metasurfaces were performed using a fiber-based THz time-domain spectroscopy (THz-TDS) system (see Supporting Information for details). Both metasurfaces show counter-propagating mode splitting as function of the angle of incidence, as shown in Figure 2a,b, which implies the observation of GMRs.…”