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Passive imaging cameras at sub-millimeter wavelengths are currently entering a new era with the development of large format arrays of direct detectors. Several of these arrays are being developed with bare absorbing meshes without any antenna coupling (lens or horn) structures. This paper uses a spectral electromagnetic model to analyze the performance of absorber based focal plane arrays in comparison...
We report on the photoresponse of 0.7-μm InP double heterojunction bipolar transistor to THz radiation of low and high intensities, when the collector is unbiased. At low intensities, the photoresponse is linear in radiation intensity. Under intense laser radiation, we observe a saturation at intensities > 15 kW/cm2, sample damaging arising around ∼ 40 kW/cm2. The photoresponse as a function of...
Interdigitated photoconductive (IPC) switches are convenient sources and detectors for terahertz (THz) time domain spectroscopy. However, reflection of the emitted or detected radiation within the device substrate can lead to echoes that inherently limits the spectroscopic resolution achievable. In this work, we design and realize low-temperature-grown-GaAs (LT-GaAs) IPC switches for THz pulse generation...
We report a new fully integrated THz Schottky detector based on vertically contacted high doped (1 · 1018/cm3) gallium arsenide (GaAs) by using a small diameter (100 nm) silver nanowire (NW) as air-bridge contact. Compared to Schottky diodes with evaporated metal contact it has lower capacitance (0.5 fF) for a high cut-off frequency as well as better zero-bias operation for a lower noise value.
This article investigates photoconductive THz detectors based on low-temperature-grown InGaAs/InAlAs with a localized Be doping profile. With this approach we address the inherent trade-off between ultrafast carrier trapping and high mobility in photoconductors. The processed detector antennas show an excellent performance and feature a detection bandwidth of more than 6 THz and a signal-to-noise...
We present a THz heterodyne detector based on a single layer graphene field effect transistor (GFET) integrated with a bowtie antenna at 400 GHz. The heterodyne detection is achieved by coupling RF and LO signals quasi-optically to the same GFET. The down converted IF signal is extracted via a coplanar stripline connected to the GFET source and drain terminals. The measured IF bandwidth is 5 GHz.
We present two terahertz detectors composed of microbolometer sensors (vanadium oxide and silicon pn diode) and metamaterial absorbers monolithically integrated into a complementary metal oxide semiconductor (CMOS) process. The metamaterial absorbers were created using the metal-dielectric-metal layers of a commercial CMOS technology resulting in low-cost terahertz detectors. The scalability of this...
This paper presents a low-cost silicon-based terahertz computed tomography system for industrial volumetric imaging. The THz-CT scanner comprises a single radiator and detector at 490 GHz and a PTFE-lens based optical train that is fixed inside a portable cage system. It features a 2.5 mm resolution limited by the effective lens aperture and offers up to 62 dB SNR in chopped and 38 dB in a continuous-wave...
Nb5N6 bolometer is a high sensitive terahertz detector at room temperature. The core part of traditional Nb5N6 bolometer is microbridge with a typical size of 3 μm × 12 μm. We have recently proposed a method using electron beam lithography (EBL) instead of UV lithography on fabrication of Nb5N6 micro bridge, which will reduce the size of the micro-bridge one to two orders of magnitude, the minimum...
We describe a near-field nanoimaging method employed to spatially map the current-induced excess noise occurring in a bilayer graphene constriction with passive scanning near-field microscope (s-SNOM). We find that the excess noise, manifesting itself as fluctuating electromagnetic evanescent fields generated on the sample surface, is discernible only in the constricted region and increases linearly...
We report on large-area photoconductive THz emitters and detectors with an LT-GaAs active region fabricated on quartz substrates using a lift-off transfer process. These devices are compared to the same LT-GaAs emitters when fabricated on the growth substrate. We find that the transferred devices show higher optical-to-THz conversion efficiencies and significantly larger breakdown fields.
Long bases RT THz standoff spectrometer is designed. GaSe91S0.09:Al(0.03 at.%) DFG of near IR lasers was seeded by THz emission from electronic system. THz generation efficiency was improved by the factor of ≥10 at principally reduced emission bandwidth, and pulse magnitude variation decreased for at least of 4–5 times.
We present the first room temperature photodection of hundreds on nanowatts using a quantum well mid-infrared detector at 9μm, with a background-limited temperature of 82K and a corresponding background-limited specific detectivity of 1.4×1010 cmHz1/2/W. The photonic architecture consists of an array of double metal nano-antennae and allows to reduce the dark current and increase the absorbed electromagnetic...
Brownout refers to dust cloud created by the rotor downwash of a helicopter. When it occurs, the visibility becomes limited, or even null. The pilot can be desorientated and accident may happen. No existing imaging systems can see through dust clouds, in real-time and with sufficient resolution. Using waves between 100GHz and 1THz seems to be a good solution to make a compact and suitable imaging...
A study of different pixel implementations working around 300 GHz is presented. They are monolithically integrated in a standard low-cost CMOS process with a high performances read-out chain for signal processing. All the different pixel configurations are compliant with the integrated metal stack and the imposed density rules of the technology. A test-chip, composed of a total of 17 cases of study,...
We present an efficient terahertz (THz) detector based on an optically thin hybrid cavity. We use experimental and numerical methods to design efficient detectors, finding a hybrid cavity structure with a photoconductive (PC) layer as thin as 50 nm which absorbs almost 80% of light at the operation wavelength. These optically thin detectors are well suited to near-field microscopy and terahertz component...
The sensitivity of state-of-the-art superconducting far-infrared detectors is such that astronomical observations at these wavelengths are limited by photon noise from the astronomical source unless a method of restricting the spectral bandpass is employed. One such method is to use a high resolution Fabry-Pérot interferometer (FPI) in conjunction with a lower resolution, post dispersing system, such...
We demonstrate a novel architecture for a THz near-field probe, which enables coherent imaging with subwavelength spatial resolution using THz quantum cascade lasers. An InAs nanowire acting as a THz detector based on the field effect transistor concept is integrated inside a subwavelength input aperture of the near-field probe to detect intensity of the THz field and its phase. To determine the phase...
The design and performance analysis are presented for a passive uncooled radiometer pixel suitable for integration in 28nm CMOS technology. In the configuration a single wideband antenna, operating from 200 GHz to 600 GHz, is connected to a pn-junction diode. Including the antenna-detector impedance mismatch, the detector shows an average NEP of 2.71 pW/√Hz such that, together with the antenna, the...
In the following work, we present the study and plans for the realization of a THz QCL based Polarimeter for fusion plasma diagnostics. The device is being developed taking into consideration a reduced footprint, reliability and ease of operation and maintenance.
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