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Current technology used for monitoring fetal well-being has been ineffective at reducing rates of harm to the fetus during the intrapartum period, yet its adoption has significantly increased the number of emergency C-sections performed. Transabdominal fetal pulse oximetry (TFO) aims to reduce the number of surgical interventions through non-invasive measurements of fetal oxygen saturation. When developing...
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 examine integration of a patterned metal nanoantenna (or metasurface) directly onto long-wave infrared detectors. These structures show significantly improved external quantum efficiency compared to their traditional counterparts. We will show simulation and experimental results.
We demonstrate the feasibility of high-resolution terahertz gas spectroscopy via the self-mixing effect in a quantum-cascade laser. Tuning the frequency of the quantum-cascade laser across a molecular absorption line of CH3OH leads to a reduction of the optical feedback, which can be detected by monitoring the voltage across the quantum-cascade laser.
In this work, we present the design of a LEKID aluminum pixel that potentially can be used as part of a detector array on a millimeter wavelength system detection to be installed on a millimeter wavelength telescope. The LEKID pixel is designed to work at 250 mK bath temperature, simulations of the optical coupling show that detector absorb EM radiation within of the 2-mm wavelength atmospheric window...
The strained layer superlattice (SLS) class of materials is a growing area of research interest for the development of high-performance mid-wavelength infrared (MWIR) detectors. InAs/(In)GaSb is the first and most thoroughly studied SLS material system, but relatively short Shockley-Reed-Hall (SRH) carrier lifetime has prompted exploration of alternative material systems. Significant improvement in...
Upconversion detection is a promising technology for measurement of IR signals in the 1.5 μm–2 μm region used for lidar remote sensing [1-2]. In comparison to conventional InGaAs detector, the upconversion detector can achieve IR detection with better signal-to-noise ratio (SNR), not only due to lower dark noise directly, but also because of its limited field-of-view and acceptance bandwidth that...
It was recently demonstrated that by adding a filter array to photodetector array, a very compact wavelength-multiplexed spectrometer can be achieved [1, 2]. These previous efforts have had both strengths and weaknesses, however. In [1], the filter array comprised etalons with different thicknesses fabricated by a multi-step process. In [2], the filter array comprised quantum dots spotted onto the...
Nanowire superconducting single-photon detectors (SSPDs) consist of a superconducting wire of nanoscale cross-section [1], typically 4×100 nm2. A current close to the device critical current renders the nanowire sensitive to single photons. SSPDs are known for their high efficiency, low jitter, low dark count rate and fast reset time. An important challenge for future application of SSPDs is to extend...
We present the optical transfer function (OTF) analysis of a spaceborne imaging sensor. This includes the effects of detector footprint, diffusion, smear, jitter, sampling, and time delay and integration. Each effect is analyzed under various design choices one of which corresponds to our designed complementary metal-oxide semiconductor imaging sensor. Effect of each subsystem is separately demonstrated...
Blood flow measurement is based on the blood of hemoglobin to absorb light capacity. The sensors are made up of light sources and detectors placed close to each other, and are placed directly on the skin when measured. The emitted light penetrates into the skin, tissues and blood vessels, and then is absorbed, transmitted and reflected. The intensity of the reflected light recorded by the detector...
It is well known that timing jitter can degrade the bit error rate (BER) of receivers that recover clock information from the input data. In this paper, we show that timing jitter can also result in an indefinite increase in the settling time of clock recovery circuits, particularly in low swing mesochronous systems. Mesochronous clock retiming circuits are used to recover a clock of the correct phase...
Exposure of the general public to low-level RF fields causes direct or indirect coupling of the fields in the human body. Due to this coupling, there is an induction of the fields inside the body tissue that causes currents in the tissue while the tissue absorbs RF power. In this work, the RF absorption by a biological tissue was measured by using an antenna trainer in a laboratory set up by varying...
We have designed, fabricated, and characterized an uncooled, multi-band sub-wavelength metamaterial detector focal plane array (FPA) for real-time multi-spectral terahertz (THz) wave sensing and imaging. A rise in temperature due to the resonant absorption by split ring resonators (SRRs) leads to an increase in the interconnected SRR array's resistance, which can be readily read out electrically....
For the first time, we demonstrate the detection of carbon dioxide (CO2) using a non-dispersive infra-red (NDIR) technique that does not require an expensive CMOS-incompatible optical filter. This is achieved by employing a differential IR thermopile detector with micro-engineered (plasmonic) optical properties, fabricated in a commercially available standard CMOS MEMS process. The proof of concept...
In PET detectors based in monolithic scintillators the interaction coordinates of each photon impact, in particular the 511 keV energy, can be determined from the light distribution sampled at the photosensors pixels. However, some of these distributions can be produced by pure dark noise from the SiPM photosensor, multi-interaction events with long travelled distance, pile-up, etc. Early rejection...
The response of VPE GaAs detectors with a polyethylene converter under fast neutron irradiation from a 241Am-Be source was measured and simulated. The detection efficiency experimentally obtained was 1.30 · 10−3 puls./neutr. The simulation of the detector characteristics has showed a good agreement with the experimental data and allowed to estimate the maximum theoretical efficiency of polyethylene...
Recently we reported on a high efficiency, low gamma-sensitivity, high count rate capable 1D neutron detector consisting of ZnS:6LiF scintillator readout with WLS-fibers coupled to SiPMs which showed a performance comparable with a 3He-based detector. In this work we discuss a possible extension of the developed technology to large area 2D detectors with high count rate capability suitable, for example,...
A direct-conversion photon-counting detector has great potential in CT imaging and has been intensively studied in recently years. However, the optimization of the detector configuration based on clinically-relevant metrics is still lacking. In this study, we developed an optimization scheme for CZT-based photon-counting detector design. The spectral response functions characterizing different detector...
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