Near-Field Spectroscopy of Individual Asymmetric Split-Ring Terahertz Resonators

Abstract

Metamaterial resonators have become an efficient and versatile platform in the terahertz frequency range, finding applications in integrated optical devices, such as active modulators and detectors, and in fundamental research, e.g., ultrastrong light−matter investigations. Despite their growing use, characterization of modes supported by these subwavelength elements has proven to be challenging and it still relies on indirect observation of the collective far-field transmission/reflection properties of resonator arrays. Here, we present a broadband time-domain spectroscopic investigation of individual metamaterial resonators via a THz aperture scanning near-field microscope (a-SNOM). The time-domain a-SNOM allows the mapping and quantitative analysis of strongly confined modes supported by the resonators. In particular, a cross-polarized configuration presented here allows an investigation of weakly radiative modes. These results hold great potential to advance future metamaterial-based optoelectronic platforms for fundamental research in THz photonics.

Deep Learning-Enhanced Inverse Modeling of Terahertz Metasurface Based on a Convolutional Neural Network Technique

“…However, challenges arise from their weak interaction with diluted biological samples. THz metasurfaces, characterized by microscale periodic structures with distinctive electromagnetic properties, offer effective solutions, including high-resolution imaging and rapid detection [3][4][5][6][7]. In the realm of biomedical science, these metasurfaces hold vast potential for advancing diagnostic and therapeutic technologies [8,9].…”

Terahertz Biosensor Engineering Based on Quasi-BIC Metasurface with Ultrasensitive Detection

“…In the past decades, abundant kinds of metamaterials have been proposed and designed. Apart from the conventional metallic metamaterials, advanced metamaterials, such as photonic crystals [9,10], all-dielectric metamaterials [11][12][13], flexible metamaterials [14,15], liquid crystal metamaterials [16,17], and so on, are designed and fabricated to provide a potential way to implement ultrasensitive sensors in the THz region [18][19][20][21][22]. The presence of largely localized electric field enhancement near the resonance frequency is the dominant mechanism for the high sensitivity of THz MSs.…”

THz harmonic generation in graphene/metamaterial active modulators

“…We here report the nonlinear harmonic generation in a graphene integrated device, implementing actively tunable metamaterial metallic array, showing a main resonance at 0.65 THz by using table top THz-TDS spectrometer. The efficient nonlinear process is attributed to the ps-long metamaterial resonance [8], enabling an efficient build-up of the electronic excitation responsible for the nonlinear process, beyond the duration of the THz incident pulses and the relaxation dynamics of graphene, of the order of 1-2 ps [9]. The transmitted spectra revealed a complex nonlinear signal, showing a clear 3 rd harmonic signal which has a positive correlation with the carriers' density and with the impinging input THz power.…”