Highly efficient absorber is of particular importance in terahertz regime as naturally occurring materials with frequency-selective absorption in this frequency band is difficult to find. Here we present the design and characterization of a broadband terahertz absorber based on heavily Boron-doped silicon (0.7676 Ω cm) grating. It is numerically demonstrated by utilizing both the zero- and firs...

The ultrafast saturable absorption in graphene is experimentally and theoretically investigated in the femtosecond (fs) time regime. This phenomenon is well-modeled with valence band depletion, conduction band filling and ultrafast intraband carrier thermalization. The latter is dominated by intraband carrier-carrier scattering with a scattering time of 8 ( +/- 3) fs, which is far beyond the ti...

We present a combined, non-simultaneous, ASCA GIS and CGRO OSSE spectrum of the Seyfert 2 galaxy, NGC 7172, and make broad band spectral fits. The only Seyfert 2 galaxy previously studied over such a broad band is NGC 4945. We find that the most probable model for the data is a power law with an exponential cutoff being affected by a neutral absorber. The best fit parameters are found to be Γ = 1.

In this study, we demonstrated a new class of frequency-switchable metamaterial absorber in the X-band. Eutectic gallium-indium (EGaIn), a liquid metal alloy, was injected in a microfluidic channel engraved on polymethyl methacrylate (PMMA) to achieve frequency switching. Numerical simulation and experimental results are presented for two cases: when the microfluidic channels are empty, and whe...

Microwave ferrites require high coercivity for their use as microwave absorbers. Strontium hexaferrite is one of the best material due to its magnetic properties , high coercivity, large unilateral magnetic anisotropy and very low cost in comparison to others make it suitable for the use as microwave components specifically microwave absorber .Strontium nano hexa ferrites were successfully synt...

X-ray spectroscopy of Seyfert 1 galaxies often reveal absorption edges resulting from photoionized gas along the line-of-sight to the central engine, the so-called warm absorber. I discuss how recent ASCA observations of warm absorber variability in MCG?6-30-15 can lead us to reject a one-zone model and, instead, have suggested a multi-zone warm absorber. The evidence for dust within the warm a...

A novel metamaterial absorber design able to operate in the C frequency band is presented, along with an analysis and a method to improve both its bandwidth and its angular stability. Simulation results for a FR4-based design are shown for comparison with existing designs. In addition, a simplified equivalent circuit is provided for a better understanding of the great angular stability and wide...