Polarization-independent tunable terahertz slow light with electromagnetically induced transparency metasurface

Abstract

Tunable slow light systems have gained much interests recently due to their efficient control of strong light-matter interactions as well as their huge potential for realizing tunable device applications. Here, a dynamically tunable polarization independent slow light system is experimentally demonstrated via electromagnetically induced transparency (EIT) in a terahertz (THz) metasurface constituted by plus and dimer-shaped resonators. Optical pump-power dependent THz transmissions through the metasurface samples are studied using the optical pump terahertz probe technique. Under various photoexcitations, the EIT spectra undergo significant modulations in terms of its resonance line shapes (amplitude and intensity contrast) leading to dynamic tailoring of the slow light characteristics. Group delay and delay bandwidth product (DBP) values are modulated from 0.915 ps to 0.42 ps and 0.059 to 0.025 as the pump fluence increases from 0 to 62.5 〖nJ cm〗^(-2). This results in tunable slow THz light with group velocities ranging from 2.18×〖10〗^5 〖m s〗^(-1) to 4.76×〖10〗^5 〖m s〗^(-1), almost 54% change in group velocity. The observed tuning is attributed to the photo-induced modifications of the optoelectronic properties of the substrate layer. The demonstrated slow light scheme can provide opportunities for realizing dynamically tunable slow light devices, delay lines, and other ultrafast devices for THz domain.

Thin film sensing near exceptional point utilizing terahertz plasmonic metasurfaces

“…The lossy Si patch is with ϵ = 11.9 and an electrical conductivity of 0.000 25 S m −1 . The conductivity (σ) of the embedded Si patch can be actively controlled [49] to achieve the conditions of the EP under different refractive indices of the overlayer. For excitation of similar LC (inductive-capacitive) resonance modes in the L-and R-SRRs, the cell parameters are kept identical, except for the inclusion of the Si patch in the L-SRR which is essential to introduce asymmetric loss.…”

“…Finally, the transmission data procured for the T xx /T yy (co-polarizations), and T xy /T yx (cross-polarizations) along the xand y-directions in terms of S parameters according to the applied conditions. The active control of the Si patch embedded in the L-SRR is carried out by varying the conductivity, which can be realized by an optical pump terahertz probe (OPTP) setup [49,54]. In the OPTP setup, the optical properties of the Si patch can be actively tailored by an external optical pump with an 800 nm pulsed laser having a beam spot diameter around ∼10 mm, with a repetition rate of 1 KHz and ∼120 fs pulse width [55,56].…”

Temperature tunable electromagnetically induced transparency in terahertz metasurface fabricated on ferroelectric platform

“…For the numerical simulations, the BTO material is modeled by using the experimentally measured complex dielectric constants shown in figure 2(d), while the MgO substrate is modeled as a dielectric with ε r = 9.6 [52]. Further, aluminum is taken as a lossy metal having a DC conductivity ∼3.7 × 10 7 S m −1 [53]. The simulations of the THz metasurface are performed with a mesh of λ/10 under periodic and open boundary conditions in the x, y and z-directions, respectively.…”

Real-Time Terahertz Modulation Using Gold-MoS2 Metasurface With Electromagnetically Induced Transparency-Like Resonance

“…However, these methods exhibit sluggish response, limiting their applicability in ultra-high-speed communication systems. In contrast, optical control, relying on the lifetimes of photoinduced carriers [17], enables ultrafast responses and has rapidly advanced [18], [19], [20], [21]. In this work, we demonstrate the modulation of resonance peak intensity by introducing MoS 2 layers into an asymmetric split-ring metasurface, creating an EIT-like resonance as THz signals traverse the engineered structure.…”