60 research outputs found
Optical waveguide mode control by nanoslit-enhanced terahertz field
The scheme is based on an optimization of the overlap between the optical waveguide mode and the THz field, with
the THz field strength enhanced by the presence of a metallic nanoslit surrounding the waveguide. We find an
optimum balance between the optical mode attenuation and Kerr-induced change in the propagation constant.
The criterion for a π∕2-cumulative phase shift, for instance for application in a Mach–Zehnder interferometer
configuration, requires 10 kV∕cm THz field, which in turn is estimated to result in a nonlinear change of the
refractive index in the waveguide of 0.001. Our simulations prove that it is quite reasonable to observe the effect
experimentally
Ultrabroadband THz spectroscopy of disordered materials
We perform THz spectroscopic investigations of the dielectric function of disordered materials in the THz region. Specifically, we consider amorphous materials and perform ultrabroadband THz spectroscopy of chalcogenide glasses where we observe the transition from universal scaling of the absorption at low frequencies to medium-range order and local order at higher frequencies
Fast Characterization of Moving Samples with Nano-Textured Surfaces
We characterize nano-textured surfaces by optical diffraction techniques
using an adapted commercial light microscope with two detectors, a CCD camera
and a spectrometer. The acquisition and analyzing time for the topological
parameters height, width, and sidewall angle is only a few milliseconds of a
grating. We demonstrate that the microscope has a resolution in the nanometer
range, also in an environment with many vibrations, such as a machine floor.
Furthermore, we demonstrate an easy method to find the area of interest with
the integrated CCD camera.Comment: 19 pages, 4 figure
Metamaterial composite bandpass filter with an ultra-broadband rejection bandwidth of up to 240 terahertz
Fabrication and characterization of terahertz anisotropic anti-rod dimer planar metamaterials
Ultrabroadband terahertz conductivity of highly doped ZnO and ITO
The broadband complex conductivities of transparent conducting oxides (TCO), namely aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO) and tin-doped indium oxide (ITO), were investigated by terahertz time domain spectroscopy (THz-TDS) in the frequency range from 0.5 to 18 THz using air plasma techniques, supplemented by the photoconductive antenna (PCA) method. The complex conductivities were accurately calculated using a thin film extraction algorithm and analyzed in terms of the Drude conductivity model. All the measured TCOs have a scattering time below 15 fs. We find that a phonon response must be included in the description of the broadband properties of AZO and GZO for an accurate extraction of the scattering time in these materials, which is strongly influenced by the zinc oxide phonon resonance tail even in the low frequency part of the spectrum. The conductivity of AZO is found to be more thickness dependent than GZO and ITO, indicating high importance of the surface states for electron dynamics in AZO. Finally, we measure the transmittance of the TCO films from 10 to 200 THz with Fourier transform infrared spectroscopy (FTIR) measurements, thus closing the gap between THz-TDS measurements (0.5-18 THz) and ellipsometry measurements (200-1000 THz). (C)2015 Optical Society of Americ
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