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We use cross-sectional scanning tunneling microscopy (STM) to reconstruct the monolayer-by-monolayer composition profile across a representative subset of MBE-grown InAs/InAsSb superlattice layers and find that antimony segregation frustrates the intended compositional discontinuities across both antimonide-on-arsenide and arsenide-on-antimonide heterojunctions. Graded, rather than abrupt, interfaces...
We observe the THz response of a multi-gate high electron mobility transistor detector structure. These devices are fabricated from single heterostructure GaAs/AlGaAs material and feature three gates: a `source gate' adjacent to source terminal, a `drain gate' adjacent to drain terminal, and a narrow `barrier gate' biased to pinch-off that serves as a bolometric sensor. Bias dependent measurements...
Broadband THZ near-field measurements were performed on different types of antennas and single elements of a metamaterial structure, all having sub-wavelength dimensions. The time and frequency dependence of the electric near-field are presented and compared with numerical calculations. Effects of the substrate are discussed.
This paper demonstrates broadband THZ near-field measurements performed on different types of antennas and meta materials structures, all having sub-wavelength dimensions. The time and frequency dependence of the electric near-field are presented and compared with numerical calculations. Using terahertz time-domain spectroscopy (THz-TDS), the electric near-field components Ex(t), Ey(t) and Ez(t) in...
Surface waves on metal films with subwavelength features and tunable optical resonances are excited with a quantum cascade laser. The resulting transmission through, and propagation on, the metal/dielectric interface is measured, both spectrally and spatially.
Summary form only given. The UCSB free-electron lasers energize two research thrusts - terahertz resonant detectors, and terahertz Bloch oscillators. Work on terahertz resonant detectors focuses on plasmonic resonances in grating gated field effect transistors. The resonant response, ~ 50 GHz wide, can be tuned with gate voltage and grating geometry. Gating a narrow region of the channel to threshold...
Gold rectangular waveguides suitable for single mode operation at frequencies near 3 THz have been micromachined using silicon microfabrication methods. The design, fabrication, and loss characteristics of these waveguides will be presented. On-chip integration of these waveguide structures with THz quantum cascade laser (QCL) sources has been achieved and the characteristics of QCL beams guided by...
Active control over the resonant frequency of a surface plasmon excitation is demonstrated. Tunable semiconductor-based extraordinary optical transmission gratings were fabricated, designed for transmission between 7 and 10μm, showing a tuning range of over 25cm−1.
We investigate the limitations of using THz metamaterials as thin-film chem-bio sensors, by depositing dielectric overlayers onto split-ring resonator arrays. We also study resonance shifts by conjugating biomolecules using avidin/silane linkers attached to the resonators.
Active control over the resonant frequency of a surface plasmon excitation is demonstrated. Tunable semiconductor-based extraordinary optical transmission gratings were fabricated, designed for transmission between 7 and 10 mum, showing a tuning range of over 25 cm-1.
This paper concentrates on another application of photonic crystals: It shows photonic crystals can be used to selectively enhance and modify the light spectra of InAs self assembled quantum dot (SAQD) emissions in mid-IR wavelengths. Quantum dots, when used as light sources, offer unique advantages. It is therefore possible to develop new devices based solely on this property of SAQD based light...
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