Free-Space Subterahertz-Field Polarization Controlled by Selection of Waveguide Modes

We experimentally study the free-space electromagnetic field emitted from a multimode rectangular waveguide equipped with a diagonal-horn antenna. Using the frequency range of 215-580 GHz, a photomixer is used to launch a free-space circularly polarized electromagnetic field, exciting multiple modes at the input of the rectangular waveguide...

Analysis of a single-mode waveguide at sub-terahertz frequencies as a communication channel

We study experimentally the transmission of an electromagnetic waveguide in the frequency range from 160 to 300 GHz. Photo-mixing is used to excite and detect the fundamental TE₁₀ mode in a rectangular waveguide with two orders-of-magnitude lower impedance. The large impedance mismatch leads to a strong frequency dependence of the...

Local Electrodynamics of a Disordered Conductor Model System Measured with a Microwave Impedance Microscope

We study the electrodynamic impedance of percolating conductors with a predefined network topology using a scanning microwave impedance microscope at gigahertz frequencies. For a given percolation number we observe strong spatial variations across a sample that correlate with the connected regions (clusters) in the network when the...

Shielded cantilever with on-chip interferometer circuit for THz scanning probe impedance microscopy

We have realized a microstrip based terahertz (THz) near field cantilever that enables quantitative measurements of the impedance of the probe tip at THz frequencies (0.3 THz). A key feature is the on-chip balanced hybrid coupler that serves as an interferometer for passive signal cancellation to increase the readout circuit sensitivity...

Nonequilibrium interpretation of DC properties of NbN superconducting hot electron bolometers

We present a physically consistent interpretation of the dc electrical properties of niobiumnitride (NbN)-based superconducting hot-electron bolometer mixers, using concepts of nonequilibrium superconductivity. Through this, we clarify what physical information can be extracted from the resistive transition and the dc current-voltage...

Spatial conductivity mapping of unprotected and capped black phosphorus using microwave microscopy

Thin layers of black phosphorus present an ideal combination of a 2Dmaterial with a tunable direct bandgap and high carrier mobility. However the material suffers from degradation in ambient conditions due to an oxidation reaction which involves water, oxygen and light. Wehave measured the spatial profile of the conductivity on flakes of...

Antenna-coupled 30 THz hot electron bolometer mixers

We report on design and characterization of a superconducting Hot Electron Bolometer Mixer integrated with a logarithmic spiral antenna for mid-IR range observations. The antenna parameters have been adjusted to achieve the ultimate performance at 10 ?m (30 THz) range where O3, NH3, CO2, CH4, N2O, …. lines in the Earth’s atmosphere, in planetary...

The electron-phonon relaxation time in thin superconducting titanium nitride films

We report on the direct measurement of the electron-phonon relaxation time, ?eph, in disordered TiN films. Measured values of ?eph are from 5.5?ns to 88?ns in the 4.2 to 1.7?K temperature range and consistent with a T?3 temperature dependence. The electronic density of states at the Fermi level N0 is estimated from measured material parameters....

Photothermoelectric response in asymmetric carbon nanotube devices exposed to sub-terahertz radiation

We report on the voltage response of carbon nanotube devices to sub-terahertz (THz) radiation. The devices contain carbon nanotubes (CNTs), which are over their length partially suspended and partially Van der Waals bonded to a SiO2 substrate, causing a difference in thermal contact. We observe a DC voltage upon exposure to 140?GHz radiation....