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Using a double-sided fabrication method, we fabricated Bi2Sr2CaCu2O8 (BSCCO) intrinsic Josephson junctions (IJJs) with a gold-BSCCO-gold structure. Coherent emission is observed at large dc input power, where a hot spot and “cold” part of the stack, coexist. The power, directly detected with a bolometer, is as high as 25 µW, implying the integrated power should be already in the order of sub-mW. We...
The reflection properties of porcine skin are examined in the terahertz (THz) frequency range utilizing a Fourier transform infrared spectrometer with a reflection unit. Their dependence on the frequency and other parameters such as the surface structure is analyzed in order to determine whether porcine skin can be used as surrogate for human skin in the THz frequency range.
A possible way to create silicon terahertz laser under electric field excitation is presented. Electrical pulses with both period and duration in nanosecond range should be applied to moderately doped stressed bulk silicon. The purpose of short pulse excitation is impurity breakdown followed by capture and population of upper lasing state. The mechanisms responsible for population inversion and losses...
We measured terahertz (THz) emission from the vertically aligned indium arsenide (InAs) nanowires using THz time-domain spectroscopy. The photoexcited InAs nanowires were grown by metalorganic chemical vapor deposition on type <111> silicon substrate. Experimental results shows that THz emission mechanism of InAs nanowires are very different from that of bulk InAs substrates.
We have developed novel THz spectrometer based on Fabry-Perot interferometer. The novelty of the device is related to the metal-covered high-resistivity silicon mirrors. Also an original body of mathematics which allows broadband incident signal spectrum reconstruction was elaborated.
We present the first findings of the THz emission from the ultra-narrow p-type Si quantum well confined by the superconductor (SC) δ-barriers on the n-type Si(100) surface. The EL spectra revealed by the voltage applied along the Si-QW plane appear to result from the value of the SC energy gap.
We report on an order-of-magnitude enhancement of sensitivity of CMOS-transistor-based THz detectors. At 2.54 THz, 3.13 THz and 4.25 THz, responsivity values of 336 V/W, 308 V/W, and 230 V/W and optimum noise-equivalent-power values of 63 pW/√Hz, 85 pW/√Hz, and 110 pW/√Hz are obtained.
A Large-scale integration (LSI) has been improved by scaling contraction. Strained Si has been proposed as a higher carrier mobility than usual. We have evaluated the strained SiGe wafer by LTEM, which is a method of analyzing to detect THz waves generated by fs laser irradiated into the sample.
We present easy-to-realize and compact terahertz bandpass filters with a high Q-factor in the order of 500. The filters are based on Fabry-Pérot reflections between two meta-surfaces, whose reflectivity is given by the design of the metal structure of the surface.
Two-dimensional electron plasma in nanometer size field effect transistors can oscillate in Terahertz (THz) frequencies, far beyond transistors fundamental cut-of frequencies. We propose an overview of some important and recent results concerning THz detection by nanometer field effect transistors. The subjects were selected in a way to stress some new aspects of the physics of nanometer scale field...
Thermal analysis of In0.53Ga0.47As and GaAs Heterostructure Barrier Varactors diodes on InP, GaAs, silicon and diamond substrates are presented. The physical dimensions of the analysed structures correspond to the dimensions of a high power integrated HBV frequency multipliers for W-band (70 – 110 GHz). It is shown that material transfer to substrates with higher thermal conductivities will reduce...
We present experimental und numerical investigations on the excitation, optimization and propagation of terahertz surface waves on silicon substrates. A single metamaterial layer is used to enhance the spatial confinement of the surface wave at the interface between air and silicon. The electric terahertz field of the surface wave is measured by a 2D near field scan.
We show that the spectrally wideband optical tunability of terahertz transmission through silicon can be strongly improved by deposition of graphene. We measured enhanced modulation up to ΔM=24% at a low modulation beam power of 40 mW and a maximal modulation depth of up to M=99%.
We demonstrate that charge carrier transport in organic semiconductor, accompanying the modulation of terahertz transmission, depends on the crystalline ordering. We could obtain charge carrier concentrations in organic semiconductor layers, pentacene thin films, on a silicon substrate.
A terahertz metamaterial comprised of C-shaped SRRs was experimentally devised and demonstrated to exhibit high-efficient and broadband anomalous refraction with strong phase discontinuities. The generalized refraction properties of the proposed metamaterial, including the effect of various incident angles and polarizations were investigated at broad terahertz frequencies. By employing such metasurface,...
Low loss broad band transmission lines are of great interest for terahertz applications. To overcome high losses, Planar Goubau Lines (PGL) have been designed and fabricated on high resistivity silicon substrate. The measured loss level is typically 1dB/mm around 250GHz. The transitions are also extremely efficient for CPW-to-PGL conversion. The loss level depends on certain parameters such as length...
We present our investigations of solar cell mini modules and metal interconnects using terahertz time-domain spectroscopic imaging. It was demonstrated, that time-domain data can be used to reveal the thickness variation of encapsulating layers and height difference of metal contact surfaces in a vicinity of shunts.
We have developed a 1D photonic crystal that can be used for sensing purposes at terahertz frequencies and which requires less then one microliter of sample material. Using this sensor we have obtained temperature dependent measurements of refractive index and extinction coefficient of glycerol in the temperature range 100 – 294 K.
We are developing an all-semiconductor plasmonic platform for mid-infrared sensing which includes growth of epitaxial n-doped germanium films, spectroscopic test and electromagnetic design of plasmonic antennas.
Silicon is widely used for solar energy harvesting applications. Here we investigate the dynamics and transport properties of photoexcited carriers in silicon nanowires by ultrafast terahertz spectroscopy. The carrier lifetime was observed to approach 0.7 ns, and the carrier mobility to be ∼1000 cm2/(Vs). We found that Silicon nanowire arrays fabricated by the metal-assisted chemical etching is better...
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