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We describe experimental measurements and simulations of a switchable THz metasurface device in a slab waveguide geometry. The device exhibits giant phase modulation of the TE1 mode at particular frequencies determined by the metamaterial geometry. Simulations predict that a 2π phase shift can be realized in an interaction length of only a few millimeters.
We present an electrically modulated nonlinear metamaterial at terahertz frequencies. The device consists of a planar array of split-ring resonators (SRRs) fabricated on n-type GaAs. Increasing the incident THz field strength induces carriers in the GaAs substrate, shorting the SRR capacitive gap and modulating the MM resonance. The application of a 15V bias to the MM reduces the net field modulation...
We describe experimental characterization of switchable THz metasurfaces using variable-angle broadband THz ellipsometry. A theoretical framework is used to extract surface susceptibility tensors as a function of frequency and applied DC bias. This will allow us to make a priori predictions of the performance of these devices for applications as metasurface active components.
We experimentally and numerically investigate a switchable dielectric-slab-waveguide metasurface device. We use an active metasurface to manipulate the interaction with a propagating THz surface wave, giving us dynamic control of the wave at 0.3 THz.
We recently demonstrated ultrathin, broadband, and highly efficient (reaching 88%) terahertz (THz) metamaterial structures exhibiting near-perfect anomalous (or generalized laws of) refraction. These structures redirect up to 61% of the incident power into the anomalous beam and practically eliminate the ordinary component. Here exploit this breakthrough to create more complex optical elements, specifically...
We demonstrate ultrathin THz metamaterials capable of high-efficiency and broadband linear polarization conversion in reflection or transmission. Through the creation of a linear phase gradient, they are further employed in the demonstration of near-perfect anomalous reflection/refraction.
We design and test a switchable diffraction grating based on active metamaterials for terahertz modulation. We observe off-axis diffraction which permits operation of the device as a high-contrast modulator, with better than 20 dB of dynamic range.
Resonant excitation of planar terahertz metamaterials using attenuated total reflection is demonstrated. Experimental results reveal an anomalous increase in the resonance strength while the sample is illuminated near the edge of the metamaterial array with a finite-size terahertz beam. A re-radiation signal at the fundamental metamaterial resonance is observed on the transmission side of the total...
We demonstrate ultrafast optical control of near field coupled metamaterial resonances. We observed dynamical transition of the metamaterial resonances to change its state from coupled to decoupled, and back to the coupled state under photoexcitation.
We design and test a switchable diffraction grating based on active metamaterials for terahertz modulation. We observe off-axis diffraction which permits operation of the device as a narrowband high-contrast modulator.
This work presents a novel approach to further decrease the thickness of the ultra thin perfect metamaterial absorbers by adjusting the geometric dimensions of the resonators. Both simulational and experimental results with a typical metamaterial absorber structure show that the thickness of the absorber decreases from ~8 μm to ~4 μm by increasing the width of the cross-resonator from 10 μm to 40...
We demonstrate broadening of fundamental resonance by successive insertion of rings inside of a split ring resonator (SRR) in a nested fashion. With the maximum inner rings, the resonance linewidth broadens by factor of four.
We demonstrate reconfigurable metamaterial by actively switching constituent resonators from split-ring to closed-ring configuration. Both fundamental and third order resonances damps out while the second order resonance emerges at high pump power.
We demonstrate the ultrafast switching and tuning of the resonance in high temperature superconducting YBCO metamaterial excited by near infrared femtosecond laser pulses. The infrared photons break the Cooper pairs thus destroys the metamaterial resonance.
We report tunable resonances in terahertz metamaterials made from high-temperature superconducting films. Taking in account the temperature-dependent complex conductivity, we develop a theoretical model for correct interpretation of the observed resonance switching and frequency tuning.
Bilayer split ring resonators as a function of separation (∼λ /500) and orientation are measured. Terahertz measurements match simulations showing frequency shifting of the resonances with implications for electrically small antenna design.
We demonstrate thermal tuning of the inductive capacitive (LC) resonance in terahertz metamaterials made up of gold split-ring resonator (SRR) arrays on ferroelectric bulk Strontium Titanate (STO) substrates. Heating the metamaterial from temperature of 150 K to 425 K causes as high as 69% blue shift in metamaterial resonance frequency due to the change in refractive index of the substrate.
We demonstrate active tuning of coupled inductive-capacitive resonance in a multi-layer metamaterial. Our experiment reveals that one resonance mode of a coupled pair can be selectively switched off by driving the metamaterial with infrared light.
Split-ring-resonators (SRR) play a significant role in the design and realization of metamaterials over a wide range of the electromagnetic spectrum. In addition to single SRR layers, a number of demonstrations have been carried out to understand the bulk properties of multiple layer structures. Usually, the SRR layers are separated by dielectrics with a layers spacing > λres/30. We present the...
Tunable optical activity in chiral metamaterials is demonstrated in simulation and shows actively tunable giant polarization rotation over a wide frequency band.
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