Detection Of Terahertz Radiation Research Articles

Photothermal, Photoelectric, and Photothermoelectric Effects in Bi-Sb Thin Films in the Terahertz Frequency Range at Room Temperature

The terahertz frequency range is promising for solving various practically important problems. However, for the terahertz technology development, there is still a problem with the lack of affordable and effective terahertz devices. One of the main tasks is to search for new materials with high sensitivity to terahertz radiation at room temperature. Bi1−xSbx thin films with various Sb concentrations seem to be suitable for such conditions. In this paper, the terahertz radiation influence onto the properties of thermoelectric Bi1−xSbx 200 nm films was investigated for the first time. The films were obtained by means of thermal evaporation in vacuum. They were affected by terahertz radiation at the frequency of 0.14 terahertz (THz) in the presence of thermal gradient, electric field or without these influences. The temporal dependencies of photoconductivity, temperature difference and voltage drop were measured. The obtained data demonstrate the possibility for practical use of Bi1−xSbx thin films for THz radiation detection. The results of our work promote the usage of these thermoelectric materials, as well as THz radiation detectors based on them, in various areas of modern THz photonics.

Uncooled Antenna-Coupled Microbolometer for Detection of Terahertz Radiation

In this contribution, we describe the design, technology, and physical parameters of antenna-coupled microbolometer, used for broadband detection of terahertz electromagnetic spectrum. This microbolometer features an application of La0.67Sr0.33MnO3 layer grown on multilayered material stack ensuring lattice matching of the sensing LSMO layer to silicon. By virtue of bulk micromachining of silicon-on-insulator substrates, the sensing structure is built on thin suspended membrane to provide weak thermal link, increasing thermal response, thus sensitivity. Additionally, it helps suppressing excitation of in-plane guided surface modes that will otherwise deteriorate the antenna radiation diagram and affect the spectral responsivity of the sensor. Finally, the operation of sensor is demonstrated using a molecular laser setup at 762 GHz (and also 1.4 THz) emission line. The parameters of the said microbolometers are analyzed in terms of response and time constant. Optimal working temperature of the detectors is about 65 °C.

Effect of Gallium Arsenide Charge Carrier Life Time on the Generation and Detection Efficiency of Continuous and Pulsed Terahertz Radiation

A configuration and test samples of photoconductive dipole antennas based on SI-GaAs:Cr and LT-GaAs for generation and detection of terahertz radiation are developed. Their operating characteristics in the pulsed mode and in the mode of operation as photomixers are experimentally investigated.

Application of the Schottky diode as a detector of continuous terahertz radiation

The results of research of the electrophysical and frequency characteristics of the semiconductor structure of a Schottky diode based on gallium arsenide are presented. The diode structure was modelled in the Sentaurus TCAD software package. A comparison of the current-voltage characteristics obtained by mathematical modeling and by experiment are presented. The frequency response in the range of 115-257 GHz is shown. The use of a Schottky diode as a continuous terahertz radiation detector is shown.

Current state and prospects of detectors in the terahertz range Part 1. Direct detection of terahertz radiation

The paper discusses the problems associated with the development of technology for terahertz radiation detectors. The main physical phenomena and recent pro-gress in various methods of detecting terahertz radiation (direct detection and het-erodyne detection) are considered. Advantages and disadvantages of direct detec-tion sensors and sensors with heterodyne detection are discussed. In part 1, a number of features of direct detection are considered and some types of terahertz direct detection detectors are described. Part 2 will describe heterodyne detection and continue to describe some types of modern photonic terahertz receivers.

Antenna coupled bolometer simulation for terahertz radiation detection diffracted by a small metal object

Terahertz (THz) wave technologies are becoming near future wireless technologies because of its advantages of considerable bandwidth and still unlicensed spectrum. Its small bandwidth offers a more compact wireless device on a scale of micrometers. Detection is a challenge for applying these potential technologies. An antenna coupled with a bolometer device is a candidate to capture emitted THz wave radiation. Another consideration can be any possible obstacles. This paper presents a simulation of Terahertz wave radiation detected with a dipole antenna connected to a bolometer. This research uses a 3D simulation software of CST Microwave Studio to simulate linearly THz plane waves radiation passing through a small metal object. Some dipole antennas coupled bolometer detect the power of the plane wave radiation in location after the emitted plane waves hit the object. The result shows that the highest detected power can be detected. Even the detector is located at the center of the area blocked by the metal object. This condition indicates that diffraction is high enough, affected by the comparable size, the metal, wavelength, and observation distances. More studies to characterize this diffraction effect are becoming useful, especially for THz imaging applications, such as metal detection for an airport security system.

Numerical modeling of highly sensitive resonant detection of THz radiation using a multichannel dispersive plasmonic HEMT

The resonant detection of terahertz radiation using a dispersive AlN/GaN multichannel high-electron-mobility transistor (HEMT) is analyzed and modeled in this paper. The proposed full-wave model is based on the concurrent solution of the complete hydrodynamic model (CHM) and Maxwell’s equations. The CHM is derived from the first three moments of the Boltzmann transport equation (BTE). Considering the variations of the electron temperature and transport parameters along the HEMT channel, this model well characterizes the electron–wave interaction in the device for both low- and high-field conditions. Moreover, the effect of the optical phonon modes of the GaN buffer, which cannot be ignored in the target terahertz frequency band, is described using the Lorentz dispersive model. Employing the developed model, the transmission spectrum of the device is extracted numerically using the finite-difference time-domain (FDTD) method for grating-gate single-, double-, and three-channel HEMT structures. The results show that, at a lattice temperature of 300 K for a GaN grating-gate HEMT with gate periodicity of 680 nm and gate width of 520 nm, at given resonance frequency and overall electron concentration, the resonance depth improves by about 2.7 dB in the three- compared with the single-channel structure. Moreover, it is shown that the detection performance of such a structure at 300 K is similar to the single-channel HEMT at a reduced temperature of 120 K. Therefore, the multichannel HEMTs can show notably improved resonant detection performance, enabling the design of resonant detectors with enhanced sensitivity at room temperature.

Review of porous core photonic crystal fibers for terahertz waveguiding

The terahertz regime lies between microwave and infrared ranges, taking up a substantial portion of the electromagnetic spectrum. Due to its unique features, terahertz radiation has received significant attention from researchers. This paper reviews the current status of Porous Core Photonic Crystal Fibers (PC-PCF) for terahertz propagation. While the review partly focuses on general introduction as well as the methods of generating and detecting terahertz radiation, an overview of the applicability of terahertz radiation in medical and telecommunication industries is provided. The paper also reviews the fundamental guiding principles and properties of PC-PCFs. The discussed optical features of PC-PCFs include effective material loss, confinement loss, bending loss, core power fraction, dispersion variation, and birefringence. A research timeline which systematically analyses proposed PC-PCFs from 2014 to 2020 is also presented. Finally, the paper discusses the most common fabrication methods of PC-PCFs.

Intense terahertz radiation: generation and application.

Strong terahertz (THz) radiation provides a powerful tool to manipulate and control complex condensed matter systems. This review provides an overview of progress in the generation, detection, and applications of intense THz radiation. The tabletop intense THz sources based on Ti:sapphire laser are reviewed, including photoconductive antennas (PCAs), optical rectification sources, plasma-based THz sources, and some novel techniques for THz generations, such as topological insulators, spintronic materials, and metasurfaces. The coherent THz detection methods are summarized, and their limitations for intense THz detection are analyzed. Applications of intense THz radiation are introduced, including applications in spectroscopy detection, nonlinear effects, and switching of coherent magnons. The review is concluded with a short perspective on the generation and applications of intense THz radiation.

High temperature metamaterial terahertz quantum detector

We demonstrate a high-temperature performance quantum detector of Terahertz (THz) radiation based on three-dimensional metamaterial. The metamaterial unit cell consists of an inductor-capacitor (LC) resonator laterally coupled with antenna elements. The absorbing region, consisting of semiconductor quantum wells, is contained in the strongly ultra-subwavelength capacitors of the LC structure. The high radiation loss of the antenna allows strongly increased collection efficiency for the incident THz radiation, while the small effective volume of the LC resonator allows intense light-matter coupling with a reduced electrical area. As a result, our detectors operate at much higher temperatures than conventional quantum well detectors demonstrated so far.

Detection of black body radiation using a compact terahertz imager

We detect terahertz radiation emitted by a blackbody object at room temperature. The probe consists of semiconductor detectors coupled to the cold finger of a compact cryo-cooler. The detectors are narrow conductive channels in two-dimensional electron gas, which is sensitive to variations of photon flux through the mechanism of excitation and rectification of plasma waves. The excitation has a resonant nature, with an unexpectedly narrow FWHM, below 10%. The key element of the concept is a compact cryo-platform, which enables us to use highly sensitive cryo-detectors, while keeping the system compact, ∼34 cm side, and mobile. We discriminate the temperature variation of the blackbody object as small as 1.0 K at a distance of 1 m. There is room for further optimization of the detectors and optical systems to boost the temperature resolution down to 0.5 K and the operation distance to 5 m, which are needed for practical applications.

Electro-optical detection of terahertz radiation in a zinc sulphide crystal at a wavelength of 512 nm

The electro-optical sampling method is a widely used technique for the detection of terahertz (THz) waves. During the last thirty years, various electro-optical sensors have been proposed, but mainly working with a near-infrared probe. Here we demonstrate efficient detection of terahertz radiation up to 2.5 THz using a (110)-cut zinc sulfide (ZnS) crystals with the second harmonic of an amplified solid-state ytterbium laser beam at 512 nm. To validate its characteristics, we compare its performance with that of the cadmium telluride (CdTe) crystal probed at the fundamental wavelength of the laser.

Terahertz Radiation Sources and Detectors Based on Optical Microcavities Embedded in the Edge Channels of Silicon Nanosandwiches

Over the past 30 years, there has been a great deal of interest in the use of terahertz (THz) radiation in various fields, such as security systems, communications, and spectroscopy. In addition, THz radiation is increasingly being used in practical medicine; in particular, the potential of THz irradiation for influencing metabolic reactions together with controlling the most important biochemical processes taking place in the human body has been demonstrated. In turn, this has stimulated the development of compact sources and detectors of THz and gigahertz (GHz) electromagnetic radiation on the basis of development of silicon optoelectronics and nanoelectronics. Silicon emitters with the ability to control THz and GHz frequency modulation are created, which enables their use for effective therapy of demyelinating diseases of the central nervous system.

Investigation of the Photosensitivity of Narrow-Gap and Gapless HgCdTe Solid Solutions in the Terahertz and Sub-Terahertz Range

The photoresponse is investigated in the frequency range of 0.15–15 THz in HgCdTe epitaxial layers with a cadmium concentration from 15.2 to 19.2% grown by molecular-beam epitaxy. It is shown that narrow-gap and gapless HgCdTe solid solutions can be used as detectors of both terahertz and sub-terahertz radiation with a characteristic response time of 2–4 ns and with a sensitivity approaching n-InSb-based detectors widely used in this range.

Singularity-Enhanced Terahertz Detection in High-Mobility Field-Effect Transistors

Detectors of high-frequency radiation based on high-electron-mobility transistors benefit from low noise, room-temperature operation, and the possibility to perform radiation spectroscopy using gate-tunable plasmon resonance. Despite successful proof-of-concept demonstrations, the responsivity of transistor-based detectors of terahertz radiation, at present, remains fairly poor. To resolve this problem, we propose a class of devices supporting singular plasmon modes, i.e., modes with strong electric fields near keen electrodes. A large plasmon-enhanced electric field results in amplified nonlinearities, and thus efficient ac-to-dc conversion. We analyse subterahertz detectors based on a two-dimensional electron system in the Corbino geometry as a prototypical and exactly solvable model, and show that the responsivity scales as $1/{r}_{0}^{2}$ with the radius of the inner contact ${r}_{0}$. This enables responsivities exceeding 10 kV/W at subterahertz frequencies for nanometer-scale contacts readily accessible by modern nanofabrication techniques.

Asymmetric dual-grating gates graphene FET for detection of terahertz radiations

A graphene-based field-effect-transistor with asymmetric dual-grating gates was fabricated and characterized under excitation of terahertz radiation at two frequencies: 0.15 THz and 0.3 THz. The graphene sheet was encapsulated between two flakes of h-BN and placed on a highly doped SiO2/Si substrate. An asymmetric dual-grating gate was implemented on the h-BN top flake. Even though no antenna was used to couple the incoming radiation, a clear gate-bias-dependent photocurrent was measured under excitation at 0.3 THz up to room temperature. We subsequently demonstrated that the device can be used for terahertz sensing and inspection of hidden metallic objects at room temperature.

Ionic Liquid Gating Enhanced Photothermoelectric Conversion in Three-Dimensional Microporous Graphene.

The photothermoelectric (PTE) effect can effectively convert light into electricity through photothermal and thermoelectric processes and has great potential applications in light energy harvesting and bandgap-independent photodetection. It is particularly applicable for the terahertz (THz) range featuring low photon energy but has not been well established due to lack of high-performance PTE materials in this range. Three-dimensional microporous graphene (3DMG) foam possesses ultrahigh THz absorptivity and outstanding photothermal conversion and can serve as a promising candidate. Here, enhancement of the THz PTE response of 3DMG foam by fine-tuning its thermoelectric properties using the ionic liquid electric double layer (EDL) technique was demonstrated. Continuous and reversible control of the Seebeck coefficient of 3DMG highlights the effectiveness of EDL gating in manipulating the electronic structures of such bulk and porous material. An approximate 1 order of magnitude enhancement in the Seebeck coefficient as well as the PTE responsivity was observed. In addition, a double-cell 3DMG EDL device with a p-n junction like channel configuration enabled further improvement of the photoresponse. This work opens a new avenue to optimize the PTE performance of 2D nanosheet-assembled 3D porous materials for highly efficient energy harvesting and detection of THz radiation.

FEM Simulation of THz Detector Based on Sb and Bi88Sb12 Thermoelectric Thin Films

A terahertz (THz) detector based on thermoelectric thin films was simulated using the finite elements method. The thermoelectric circuit consisted of S b and B i 88 S b 12 150-nm films on the mica substrate. S b , B i 88 S b 12 , and mica-substrate properties have been measured experimentally in the THz frequency range. The model of electromagnetic heating was used in order to estimate possible heating of S b - B i 88 S b 12 contact. THz radiation power varied from 1 μ W to 50 mW, and frequency varied in the range from 0.3 to 0.5 THz. The calculations showed a temperature difference of up to 1 K, voltage up to 0.1 mV, and responsivity of several mVW − 1 . The results show that thin S b and B i − S b thermoelectric films can be used for THz radiation detection at room temperatures.

Исследования фоточувствительности узкозонных и бесщелевых твердых растворов HgCdTe в терагерцовом и субтерагерцовом диапазоне частот

Abstract The photoresponse is investigated in the frequency range of 0.15–15 THz in HgCdTe epitaxial layers with a cadmium concentration from 15.2 to 19.2% grown by molecular-beam epitaxy. It is shown that narrow-gap and gapless HgCdTe solid solutions can be used as detectors of both terahertz and sub-terahertz radiation with a characteristic response time of 2–4 ns and with a sensitivity approaching n -InSb-based detectors widely used in this range.

Определение влияния времени жизни носителей заряда арсенида галлия на эффективность непрерывной и импульсной генерации и детектирования излучения терагерцового диапазона частот

A configuration and test samples of photoconductive dipole antennas based on SI-GaAs: Cr and LT-GaAs for terahertz radiation generation and detection were developed. Their operating characteristics in pulsed mode and in the mode of operation as photomixers was experimentally investigated.