188 research outputs found
Terahertz Radiation Detection by Field Effect Transistor in Magnetic Field
We report on terahertz radiation detection with InGaAs/InAlAs Field Effect
Transistors in quantizing magnetic field. The photovoltaic detection signal is
investigated at 4.2 K as a function of the gate voltage and magnetic field.
Oscillations analogous to the Shubnikov-de Haas oscillations, as well as their
strong enhancement at the cyclotron resonance, are observed. The results are
quantitatively described by a recent theory, showing that the detection is due
to rectification of the terahertz radiation by plasma waves related
nonlinearities in the gated part of the channel.Comment: 4 pages, 3 figure
Helicity sensitive terahertz radiation detection by dual-grating-gate high electron mobility transistors
We report on the observation of a radiation helicity sensitive photocurrent
excited by terahertz (THz) radiation in dual-grating-gate (DGG)
InAlAs/InGaAs/InAlAs/InP high electron mobility transistors (HEMT). For a
circular polarization the current measured between source and drain contacts
changes its sign with the inversion of the radiation helicity. For elliptically
polarized radiation the total current is described by superposition of the
Stokes parameters with different weights. Moreover, by variation of gate
voltages applied to individual gratings the photocurrent can be defined either
by the Stokes parameter defining the radiation helicity or those for linear
polarization. We show that artificial non-centrosymmetric microperiodic
structures with a two-dimensional electron system excited by THz radiation
exhibit a dc photocurrent caused by the combined action of a spatially periodic
in-plane potential and spatially modulated light. The results provide a proof
of principle for the application of DGG HEMT for all-electric detection of the
radiation's polarization state.Comment: 7 pages, 4 figure
Plasmonic terahertz detection by a double-grating-gate field-effect transistor structure with an asymmetric unit cell
Plasmonic terahertz detection by a double-grating gate field-effect
transistor structure with an asymmetric unit cell is studied theoretically.
Detection responsivity exceeding 8 kV/W at room temperature in the photovoltaic
response mode is predicted for strong asymmetry of the structure unit cell.
This value of the responsivity is an order of magnitude greater than reported
previously for the other types of uncooled plasmonic terahertz detectors. Such
enormous responsivity can be obtained without using any supplementary antenna
elements because the double-grating gate acts as an aerial matched antenna that
effectively couples the incoming terahertz radiation to plasma oscillations in
the structure channel.Comment: Submitted to APL, 8 pages, 2 figure
High performance bilayer-graphene Terahertz detectors
We report bilayer-graphene field effect transistors operating as THz
broadband photodetectors based on plasma-waves excitation. By employing
wide-gate geometries or buried gate configurations, we achieve a responsivity
and a noise equivalent power in the 0.29-0.38 THz range, in photovoltage and photocurrent mode.
The potential of this technology for scalability to higher frequencies and the
development of flexible devices makes our approach competitive for a future
generation of THz detection systems
Graphene field-effect transistors as room-temperature terahertz detectors.
The unique optoelectronic properties of graphene make it an ideal platform for a variety of photonic applications, including fast photodetectors, transparent electrodes in displays and photovoltaic modules, optical modulators, plasmonic devices, microcavities, and ultra-fast lasers. Owing to its high carrier mobility, gapless spectrum and frequency-independent absorption, graphene is a very promising material for the development of detectors and modulators operating in the terahertz region of the electromagnetic spectrum (wavelengths in the hundreds of micrometres), still severely lacking in terms of solid-state devices. Here we demonstrate terahertz detectors based on antenna-coupled graphene field-effect transistors. These exploit the nonlinear response to the oscillating radiation field at the gate electrode, with contributions of thermoelectric and photoconductive origin. We demonstrate room temperature operation at 0.3 THz, showing that our devices can already be used in realistic settings, enabling large-area, fast imaging of macroscopic samples
Geometrical Aberration Suppression for Large Aperture Sub-THz Lenses
Advanced THz setups require high performance optical elements with large numerical apertures and small focal lengths. This is due to the high absorption of humid air and relatively low efficiency of commercially available detectors. Here, we propose a new type of double-sided sub-THz diffractive optical element with suppressed geometrical aberration for narrowband applications (0.3 THz). One side of the element is designed as thin structure in non-paraxial approach which is the exact method, but only for ideally flat elements. The second side will compensate phase distribution differences between ideal thin structure and real volume one. The computer-aided optimization algorithm is performed to design an additional phase distribution of correcting layer assuming volume designing of the first side of the element. The experimental evaluation of the proposed diffractive component created by 3D printing technique shows almost two times larger performance in comparison with uncorrected basic diffractive lens
Room Temperature Coherent and Voltage Tunable Terahertz Emission from Nanometer-Sized Field Effect Transistors
We report on reflective electro-optic sampling measurements of TeraHertz
emission from nanometer-gate-length InGaAs-based high electron mobility
transistors. The room temperature coherent gate-voltage tunable emission is
demonstrated. We establish that the physical mechanism of the coherent
TeraHertz emission is related to the plasma waves driven by simultaneous
current and optical excitation. A significant shift of the plasma frequency and
the narrowing of the emission with increasing channel's current are observed
and explained as due to the increase of the carriers density and drift
velocity.Comment: 3 figure
Field effect transistors for terahertz detection - silicon versus III–V material issue
International audienceResonant frequencies of the two-dimensional plasma in FETs reach the THz range for nanometer transistor channels. Non-linear properties of the electron plasma are responsible for detection of THz radiation with FETs. Resonant excitation of plasma waves with sub-THz and THz radiation was demonstrated for short gate transistors at cryogenic temperatures. At room temperature, plasma oscillations are usually over-damped, but the FETs can still operate as efficient broadband THz detectors. The paper presents the main theoretical and experimental results on detection with FETs stressing their possible THz imaging applications. We discuss advantages and disadvantages of application of III-V GaAs and GaN HEMTs and silicon MOSFETs
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