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We have designed, fabricated and measured electrically-driven active metamaterials which operate as external modulators for TeraHertz Quantum Cascade Lasers. The modulation is achieved by applying a voltage to the metamaterial layer which actively displaces carriers from the n-doped layer causing changes in damping and frequency location of the lowest metamaterial response. We demonstrate their operation...
Metamaterials are engineered materials which offer superb electromagnetic performance over naturally occurring materials, and offer great potential to construct novel devices operating in the terahertz frequency regime. Here we experimentally demonstrate metamaterial narrow band filters, perfect absorbing elements for THz imaging, and ultra-fast THz switches. Experiments are supplanted with simulation...
We demonstrate metamaterial absorbers which control the emissivity spectrum of a body at a particular temperature over a bandwidth of 50%, and may be applied as coatings to materials to control their blackbody emission spectra.
Flexible resonant terahertz metamaterials built on ultrathin highly flexible polyimide substrates have been designed, fabricated and measured. Our results provide a path forward for creating multi-layer non-planar metamaterials at terahertz frequencies.
We have designed, fabricated and measured a first generation external modulator for a ~2.4 terahertz quantum cascade laser based on an electrically-driven active terahertz metamaterial structure.
We demonstrate hybrid metamaterial devices that are able to electrically switch their resonances therefore the terahertz transmission properties at room temperature. The interrelated amplitude switching and phase shifting allow for fast broadband external terahertz modulation.
We present the design, fabrication and characterization of a highly flexible metamaterial absorber that experimentally obtains an absorptivity of 0.96 at 1.6 THz and operates over wide angular range for transverse electric and transverse magnetic radiation.
In this paper, we present a metamaterial with simultaneously negative electric and magnetic resonance responses in the terahertz (THz) frequency range. The structure is composed of in-plane split resonator rings (SRRs) for desired electric response and out-of-plane SRRs realized by bimaterial pop up structures for magnetic response. Experimental results conducted using THz Time Domain Spectroscopy...
In this work, we present flexible metamaterials on free standing polyimide substrates operating at terahertz (THz) frequencies range. The successful demonstration of THz flexible metamaterials provides a path forward for creating multi-layer non-planar metamaterials such as THz invisible cloak. We also present a design for a metamaterial cylindrical shell capable of acting as an invisible cloak at...
Metamaterials are engineered materials which offer superb electromagnetic performance over naturally occurring materials, and offer great potential to construct novel devices operating in the terahertz frequency regime. Here we experimentally demonstrate metamaterial narrow band filters, perfect absorbing elements for THz imaging, and ultra-fast THz switches. Experiments are supplanted with simulation...
In this work, we demonstrate THz metamaterials exhibiting either amplitude control, via carrier injection or depletion in the active semiconductor substrate or frequency control, via photoexcitation of carriers into active semiconducting materials incorporated into the sub-wavelength metamaterial structure.
THz radiation transmission through a dual-band electric metamaterial is presented, where we analyze manufacturing defects in the metamaterial. Removing different resonator percentages allows us to quantify the effects of manufacturing defects on the material response.
We present a hybrid metamaterial semiconductor device capable of 20% tunability of the center resonance frequency via photoexcitation of the semiconductor regions, thereby addressing the metamaterials drawback of narrow bandwidth operation.
We present terahertz metamaterials fabricated on large-area, free-standing thin (les1 mum) silicon nitride membranes with the aim of reducing dielectric losses, enhancing metamaterial sensing capabilities, and enabling flexible and conformable designs.
We present experimental results of metamaterials operating at terahertz and mm-wave frequencies. Metamaterials consist of a single layer of 200 nm thick gold on a doped or undoped semiconducting substrate. By optical and electronic doping of supporting semiconducting substrates we show external control of planar arrays of metamaterials, characterized with terahertz time domain spectroscopy. Both methods...
Real-time control of terahertz metamaterial has been experimentally demonstrated through an electrical approach. The THz switching and modulation capabilities are realized by the external voltage bias to a planar hybrid metamaterial-semiconductor structure.
Planar electric metamaterials are studied with terahertz time-domain spectroscopy in transmission and reflection. Energy absorption of 5-20% due to Ohmic losses within the metal patterning is observed at resonant frequencies. Finite-element simulations verify experimental results.
Compared to the neighboring infrared and microwave regimes, the terahertz (1 THz = 1012 Hz) regime is still in need of fundamental technological advances. This derives, in part, from a paucity of naturally occurring materials with useful electronic or photonic properties at terahertz frequencies. This results in formidable challenges in the generation, detection, and creation of devices to efficiently...
We present experimental results of metamaterials operating at terahertz and mm-wave frequencies. Metamaterials consist of a single layer of 200 nm thick gold on a doped or undoped semiconducting substrate. By optical and electronic doping of supporting semiconducting substrates we show external control of planar arrays of metamaterials, characterized with terahertz time domain spectroscopy. Both methods...
Utilizing terahertz time domain spectroscopy, we characterized the electromagnetic response of planar split ring resonators fabricated on GaAs. Optical excitation is sufficient to turn off the electric resonance demonstrating the potential of SRR terahertz switches.
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