Gregory Gäumann
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View article: Report describing the comparison of material parameter measurements at millimetre-wave and THz frequencies
Report describing the comparison of material parameter measurements at millimetre-wave and THz frequencies Open
This pilot study was part of the EMPIR (18SIB09) TEMMT project and was registered as the EURAMET 1514 comparison. Therein, different methods for material parameter measurements in the THz spectral range were compared. The different measure…
View article: Standard Load Method: A New Calibration Technique for Material Characterization at Terahertz Frequencies
Standard Load Method: A New Calibration Technique for Material Characterization at Terahertz Frequencies Open
Measuring the material parameters with a vector network analyzer (VNA) usually requires time-domain gating and complicated free-space calibrations. At terahertz frequencies, classic calibrations become more problematic and uncertainty calc…
View article: Analytical Uncertainty Evaluation of Material Parameter Measurements at THz Frequencies
Analytical Uncertainty Evaluation of Material Parameter Measurements at THz Frequencies Open
Material parameter extraction algorithms are studied and simplified both for transmission-reflection and transmission-only methods. The simplified relations, which are closed-form in some cases, are analyzed to establish the uncertainty se…
View article: Measurement of four-photon absorption in GaP and ZnTe semiconductors
Measurement of four-photon absorption in GaP and ZnTe semiconductors Open
Intensity-dependent effective four-photon absorption (4PA) coefficients in GaP and ZnTe semiconductors were measured by the z-scan method using pump pulses of 1.75 µm wavelength, 135 fs duration, and up to 500 GWcm −2 intensity. A nonlinea…
View article: Material Parameter Extraction in THz Domain, Simplifications and Sensitivity Analysis
Material Parameter Extraction in THz Domain, Simplifications and Sensitivity Analysis Open
Classic equations for material parameter extraction are reconsidered and slightly modified to achieve stable results at all frequencies. Meanwhile, closed-form solutions are developed to simplify the material parameter extraction process a…
View article: Nonlinear THz spectroscopy and simulation of gated graphene
Nonlinear THz spectroscopy and simulation of gated graphene Open
We studied the nonlinear optical properties of single layer graphene using high terahertz (THz) fields. With the use of a back gate and cooling down the sample to cryogenic temperatures we are able to spectrally probe the nonlinear THz pro…
View article: Strong field transient manipulation of electronic states and bands
Strong field transient manipulation of electronic states and bands Open
In the present review, laser fields are so strong that they become part of the electronic potential, and sometimes even dominate the Coulomb contribution. This manipulation of atomic potentials and of the associated states and bands finds …
View article: High-energy terahertz pulses from semiconductors pumped beyond the three-photon absorption edge
High-energy terahertz pulses from semiconductors pumped beyond the three-photon absorption edge Open
A new route to efficient generation of THz pulses with high-energy was demonstrated using semiconductor materials pumped at an infrared wavelength sufficiently long to suppress both two- and three-photon absorption and associated free-carr…
View article: Comparison of Thermal Detector Arrays for Off-Axis THz Holography and Real-Time THz Imaging
Comparison of Thermal Detector Arrays for Off-Axis THz Holography and Real-Time THz Imaging Open
In terahertz (THz) materials science, imaging by scanning prevails when low power THz sources are used. However, the application of array detectors operating with high power THz sources is increasingly reported. We compare the imaging prop…