Terahertz Metamaterials with Semiconductor Split-Ring Resonators for Magnetostatic Tunability

Thermal tunability in terahertz metamaterials fabricated on strontium titanate single crystal substrates

We report an experimental demonstration of thermal tuning of resonance frequency in a planar terahertz metamaterial consisting of a gold split-ring resonator array fabricated on a bulk single crystal strontium titanate (SrTiO3) substrate. Cooling the metamaterial starting from 409 K down to 150 K causes about 50% shift in resonance frequency as compare to its room temperature resonance, and there is very little variation in resonance strength. The resonance shift is due to the temperature-dependent refractive index (or the dielectric constant) of the strontium titanate. The experiment opens up…

Gate-Voltage Tunability of Plasmons in Single and Multi-layer Graphene Structures: Analytical Description and Concepts for Terahertz Devices

The strong light-matter interaction in graphene over a broad frequency range has opened up a plethora of photonics applications of graphene. The goal of this paper is to present the voltage tunability of plasmons in gated single- and multi-layer graphene structures. Device concepts for plasmonic interconnects and antennas and their performance for THz communication are presented. For the first time, the role of gate voltage and the thickness of the gate dielectric on the characteristics of plasmon propagation in graphene are quantified by accounting for both the interface trap capacitance and …

基于范德华铁电体NbOI$_2$的超快可调谐强太赫兹发射

Colossal terahertz emission with ultrafast tunability based on van der Waals ferroelectric NbOI$_2$

本文发现范德华铁电半导体NbOI$_2$具有比ZnTe高一个数量级的太赫兹发射效率，并揭示了其与铁电极化相关的机制，同时演示了双泵浦方案下的超快相干调控，为高性能太赫兹器件奠定基础。

Mechanism and modulation of terahertz generation from a semimetal - graphite

Semi-metals might offer a stronger interaction and a better confinement for terahertz wave than semiconductors, while preserve tunability. Particularly, graphene-based materials are envisioned as terahertz modulators, filters and ultra-broadband sources. However, the understanding of terahertz generation from those materials is still not clear, thus limits us recognizing the potential and improving device performances. Graphite, the mother material of graphene and a typical bulk semi-metal, is a good system to study semi-metals and graphene-based materials. Here we experimentally modulate and …

Photoinduced tunability of the Reststrahlen band in 4H-SiC

Materials with a negative dielectric permittivity (e.g. metals) display high reflectance and can be shaped into nanoscale optical-resonators exhibiting extreme mode confinement, a central theme of nanophotonics. However, the ability to $actively$ tune these effects remains elusive. By photoexciting free carriers in 4H-SiC, we induce dramatic changes in reflectance near the "Reststrahlen band" where the permittivity is negative due to charge oscillations of the polar optical phonons in the mid-infrared. We infer carrier-induced changes in the permittivity required for useful tunability (~ 40 cm…

Density-independent plasmons for terahertz-stable topological metamaterials

To efficiently integrate cutting-edge terahertz technology into compact devices, the highly confined terahertz plasmons are attracting intensive attentions. Compared to plasmons at visible frequencies in metals, terahertz plasmons, typically in lightly doped semiconductors or graphene, are sensitive to carrier density (n) and thus have an easy tunability, which, however, leads to unstable or imprecise terahertz spectra. By deriving a simplified but universal form of plasmon frequencies, here we reveal a unified mechanism for generating unusual n-independent plasmons (DIPs) in all topological s…