The low energy germanium detector (LEGe) is in all aspects optimised for performance at low and moderate energies. It has specific advantages over conventional planar or coaxial detectors. LEGe is a kind of semiconductor detector commonly used in X-ray detection. It can display the spectrum of X-ray and record photon counts. Photon fluence is used to describe the radiation field by recording the number of incident photons. In order to take full advantage of the low energy response of this intrinsically thin window detector, LEGe cryostats are usually equipped with a beryllium window, thin front and side contact allowing spectroscopy from 3 keV and above. The rear contact is of less than full area which gives a lower detector capacitance compared to a planar device of similar size. It is widely used in low energy gamma spectroscopy, X-ray absorption spectroscopy, nuclear safeguards or X-ray fluorescence spectrometer and X-ray diffraction. Spectrum is an intuitional and accurate description of X-ray radiation. In this work, experiment was carried out to calibrate the detector and test the spectrum, and then to calculate the energy resolution. The experiment results about energy resolution (full width at half maximum) are 222 eV (@5.9 keV) and 519 eV (@122 keV).

The authors present an adaptive algorithm based on a non-linear regression model for mitigating time-varying etalon drifts in line-scanned optical absorption spectrometers. By dynamically varying the etalon spectral background using physically realistic degrees of freedom, the authors’ dynamic etalon fitting-routine (DEF-R) significantly increases the spectral baseline recalibration interval as compared to conventional fringe subtraction models. They provide an empirical demonstration of the efficacy of DEF-R using an on-chip 10 cm silicon waveguide for near-infrared methane absorption spectroscopy at 6057 cm⁻¹, which suffers significant etalon spectral noise due to reflections and multi-path interference from stochastic line-edge roughness imperfections. They demonstrate the corresponding improvement in both spectral clean-up and long-term stability via Allan-variance analysis. For the sensor presented here, application of DEF-R enables Gaussian-noise limited performance for more than 10² s and provides almost an order-of-magnitude improvement in stability time with respect to conventional baseline subtraction. Although DEF-R is applied here to an on-chip sensor embodiment, they envision their technique to be applicable to any absorption sensor limited by time-varying etalon drifts.

A detailed study of the performance analysis of a low-cost PIN/heterojunction bipolar transistor (HBT) opto-electronic integated circuit (OEIC) is described. Measured and of 54 and 57 GHz for 10 × 10 µm² HBTs were achieved for such a large emitter size. The base and collector regions of the transistor were utilised to form a PIN photodiode which has a dc responsivity and quantum efficiency of 0.5 A/W and 0.45, respectively, without antireflection coating at a wavelength of 1.55 µm. For both active devices, a model was realised taking all parasitic and physical-based impacts into account, for example, equivalent circuit of the pads surrounding the devices and transit delay time across the collector depletion region. The simulation results of the discrete passive and active elements showed good agreement with experimental measurements. The OEIC module was implemented in Keysight-advanced design system software with a three-stage preamplifier which has a transimpedance gain of 40 dB Ω and a −3 dB bandwidth of 18 GHz. This corresponds to a transimpedance-gain product of 1.8 THz. A series peaking inductor technique was used in the design, contributing to an enhancement in the opto-electrical bandwidth of >60%. The optical/electrical response offers a bandwidth of ∼15 GHz, adequate for up to 20 Gb/s data rate operation.

The waveguide gate-type mechanism on micro-channel plate substrate was .rstly put forward for the complex photo detection in Free space optical communication (FSO). Based on the losses of energy coupling between both Micro-channel plates (MCP), we further proposed waveguide gate-type complex detecting mechanism, which was veri.ed in electron optic system by vacuum testing. With the application of the complex detecting mechanism, the device performance has greatly improved, including higher space optical transfer and wider dynamic detecting range.

Quantum dot infrared photodetectors (QDIPs) are receiving attention as next generation infrared photodetectors that offer high-sensitivity and high-temperature operation. The realisation of QDIPs on silicon (Si) substrates offer further great advantages in terms of cost reduction and higher-resolution focal plane arrays. Indium arsenide/gallium arsenide QDIPs grown directly on on-axis Si (100) substrates are demonstrated. These are expected to further reduce fabrication costs by utilising both the monolithic integration of QDIPs with Si readout integrated circuits and also the bare substrate cost (compared with offcut Si substrates). In the device, the peak detectivity at a temperature of 32 K is measured to be 5.8 × 10⁷ cm Hz^1/2/W of 6.2 μm at a bias 0.6 V, with a corresponding responsivity of 27 mA/W. This result indicates that QD structures directly grown on on-axis Si substrates are very promising for the realisation of high-performance QDIPs with low fabrication cost.

This study theoretically analyses the performance of multiple quantum well infrared photodetector mainly with the variation of active layer doping. However, the effect of temperature and applied bias has also been studied. Results show that the effect of doping on the responsivity is significant whereas on the dark current is less significant. Effect of temperature on the dark current is more significant compared with that of doping concentration. Moreover, concerning the detectivity of the device, choice of doping plays a significant role on the detector.

Dual single-photon avalanche photodiodes (SPADs) integrated on the same chip enable the effective compensation of dark count rate (DCR) in the SPAD and also the real-time monitoring of the chip temperature. In the design, two identical SPADs are fabricated on the same chip, one operating normally and the other one covered by a metal layer to be kept in the dark. The two SPADs are identically biased and connected to identical active quench and reset integrated circuits. As both detectors are identical in structure, the dark count is expected to be similar for both. Experimental measurements show that the two SPADs exhibit similar DCR performance over a range of bias voltages and temperatures. By measuring the DCR from the covered SPAD, the DCR from the normally operated SPAD can be accounted for directly. This can be particularly useful for SPADs, where the DCR is high. Experiments under illumination show that the shaded SPAD is immune to illumination over a wide range of incident light power. This enables the real-time monitoring of the temperature on the sensor chip using the counting rate from the dark operated avalanche photodiode (APD).

Deriving a person's energy expenditure accurately forms the foundation for tracking physical activity levels across many health and lifestyle monitoring tasks. In this study, the authors present a method for estimating calorific expenditure from combined visual and accelerometer sensors by way of an RGB-Depth camera and a wearable inertial sensor. The proposed individual-independent framework fuses information from both modalities which leads to improved estimates beyond the accuracy of single modality and manual metabolic equivalents of task (MET) lookup table based methods. For evaluation, the authors introduce a new dataset called SPHERE_RGBD  +  Inertial_calorie, for which visual and inertial data are simultaneously obtained with indirect calorimetry ground truth measurements based on gas exchange. Experiments show that the fusion of visual and inertial data reduces the estimation error by 8 and 18% compared with the use of visual only and inertial sensor only, respectively, and by 33% compared with a MET-based approach. The authors conclude from their results that the proposed approach is suitable for home monitoring in a controlled environment.

Colloidal quantum dots represent a breakthrough technology for the development of optical devices, in particular photodetectors. However, the performance of CQDs photodetectors show strong aging phenomena. To solve this problem, we investigate the degradation of NIR photodetectors based on lead sulphide CQDs as a function of time and propose a viable solution to improve their time drift. The approach is based on a polymer or resin deposition for the device passivation. The devices were measured over a long time span and passivated detectors were compared to as grown ones. The results show a reduced drift of the passivated devices.

In this paper, the design of a graphene/silicon photodetector working at both 2 μm and room temperature is reported. The device is a Schottky diode and the absorption mechanism is based on the internal photoemission effect. In order to quantify the performance of the photodetector, quantum efficiency, dark current density and efficiency-dark current density ratio, are numerically calculated. Performance comparison of our proposed device with typical Schottky photodetectors based on metals, is reported. Graphene/silicon devices show a promising efficiency of 23.66% at 2 micron, a dark current density of only 0.81 nA/μm² and a quantum efficiency-dark current density ratio of about 2.93 cm²/A. This photodetector can find applications in trace-gas detection, medical sensing, environmental monitoring industrial process control.