Hybrid three-dimensional dual- and broadband optically tunable terahertz metamaterials

Abstract

The optically tunable properties of the hybrid three-dimensional (3D) metamaterials with dual- and broadband response frequencies are theoretically investigated in the terahertz spectrum. The planar double-split-ring resonators (DSRRs) and the standup double-split-ring resonators are fabricated on a sapphire substrate, forming a 3D array structures. The bi-anisotropy of the hybrid 3D metamaterials is considered because the stand-up DSRRs are not symmetrical with respect to the electric field vector. Due to the electric and magnetic response realized by the planar and the standup double-split-ring resonators respectively, the dual-band resonance response and the negative refractive index can be achieved. The potential of the phase modulation under photoexcitation is also demonstrated. Further analysis indicates that, photoexcitation of free carriers in the silicon within the capacitive region of the standup DSRRs results in a broad resonance response bandwidth (about 0.47 THz), and also functions as a broadband negative refractive index that roughly lies between 0.80 and 2.01 THz. This tunable metamaterials is proposed for the potential application of electromagnetic wave propagation in terahertz area.

Tunable Dual-Band Ultrasensitive Stereo Metamaterial Terahertz Sensor

“…For these reasons, the SDSRR sensor performs much better than other vertical metamaterial sensors. Although the vertical SRR structures had been analyzed, fabricated, and presented by several groups [50,51,52,53,54,55,56], the complexity of vertical metamaterial structure and our limited processing conditions results in lacking of test results. An assumption for SDSRR structure processing is introduced in the Supplementary documentation, but future studies will need to verify this processing.…”

A broadband tunable terahertz negative refractive index metamaterial

“…Further, the basic mechanism of NIMs condition is ε 1 μ 2 + ε 2 μ 1 < 0 (the permittivity ε = ε 1 + i ε 2 , the permeability μ = μ 1 + i μ 2 ) instead of both ε 1 and μ 1 being negative simultaneously 6 . Thus, the NIMs of double-negative MMs with simultaneous negative ε 1 and μ 1 and single-negative MMs with single negative ε 1 or μ 1 can be obtained by tailoring the geometry 7 or configuring the unit structure arrays 8 . The electromagnetic response of the MMs can be dynamically controlled by changing illumination 9 , temperature 10 and voltage etc 11 , and the controllable characteristics of the MMs are particularly important for manipulating electromagnetic radiation at terahertz (THz) frequencies where the nature material response is somewhat rare.…”

“…Accordingly, THz MMs based on three-dimensional 3D standing structures have been fabricated and characterized, and unfortunately, due to the strong bi-anisotropy of the structure, the refractive index is always positive despite of the ε 1 and μ 1 presenting negative values 17 , 18 . Although the 3D THz NIMs based on standing structure have been achieved, they are sensitive to the polarizations and incident angles, and exhibit a strong bi-anisotropy as well owing to the asymmetric structure 8 , 19 . Besides, the 3D THz NIMs composed of stacking up multiple fishnet functional layers indicates high figure of merit (FOM) 20 – 22 , but the NRI band with the FOM higher than 10 is narrow, and the ability to control refractive index is low.…”

Gigahertz Optomechanical Modulation by Split-Ring-Resonator Nanophotonic Meta-Atom Arrays

“…Another promising avenue for applications involves the use of active metamaterials for wave control 8 ; at optical or infrared frequencies, for example, various methods of modulating the effective parameters of the metamaterial to this end have been demonstrated, such as photoswitching 9,10 , heating and cooling (i.e thermal control) [11][12][13] , the use of phase-change materials 14,15 , electrooptic materials 16,17 , or coupling with microelectromechanical systems [17][18][19] . In particular, in the case of SRRbased metamaterials, active control of their optical or infrared properties has been conducted by many groups using photoswitching or electrooptic control [20][21][22][23] , phase-A different route to such modulation is the use of phonons, which promise ultrahigh frequency operation and control. Ulbricht et al 29 used GHz acoustic phonons to modulate the transmission of a metalayer consisting of an array of nanoholes in a gold film, and O'Brien et al 30 made use of GHz acoustic phonons in nanoscale gold Swiss-cross arrays with different lengths of horizontal and vertical arms to modulate linearly polarized light.…”

“…Another promising avenue for applications involves the use of active metamaterials for wave control; at optical or infrared frequencies, for example, various methods of modulating the effective parameters of the metamaterial to this end have been demonstrated, such as photoswitching, , heating and cooling (i.e thermal control), − the use of phase-change materials, , electrooptic materials, , or coupling with microelectromechanical systems. − In particular, in the case of SRR-based metamaterials, active control of their optical or infrared properties has been conducted by many groups using photoswitching or electrooptic control, − phase-change materials, , or mechanical deformations, − for example.…”