Quantitative thermal imaging using single-pixel Si APD and MEMS mirror
2018
Hobbs, M and Grainger, MP and Zhu, C and Tan, CH and Willmott, J
Accurate quantitative temperature measurements are difficult to achieve using focal-plane array sensors. This is due to reflections inside the instrument and the difficulty of calibrating a matrix of pixels as identical radiation thermometers. Size-of-source effect (SSE), which is the dependence of an infrared temperature measurement on the area surrounding the target area, is a major contributor to this problem and cannot be reduced using glare stops. Measurements are affected by power received from outside the field-of-view (FOV), leading to increased measurement uncertainty. In this work, we present a micromechanical systems (MEMS) mirror based scanning thermal imaging camera with reduced measurement uncertainty compared to focal-plane array based systems. We demonstrate our flexible imaging approach using a Si avalanche photodiode (APD), which utilises high internal gain to enable the measurement of lower target temperatures with an effective wavelength of 1 μm and compare results with a Si photodiode. We compare measurements from our APD thermal imaging instrument against a commercial bolometer based focal-plane array camera. Our scanning approach results in a reduction in SSE related temperature error by 66 °C for the measurement of a spatially uniform 800 °C target when the target aperture diameter is increased from 10 to 20 mm. We also find that our APD instrument is capable of measuring target temperatures below 700 °C, over these near infrared wavelengths, with D* related measurement uncertainty of ± 0.5 °C.
doi:
Smartphone spectrometers
2018
McGonigle, AJS and Wilkes, TC and Pering, TD and Willmott, JR and Cook, JM and Mims, FM and Parisi, AV
© 2018 by the authors. Licensee MDPI, Basel, Switzerland. Smartphones are playing an increasing role in the sciences, owing to the ubiquitous proliferation of these devices, their relatively low cost, increasing processing power and their suitability for integrated data acquisition and processing in a ‘lab in a phone’ capacity. There is furthermore the potential to deploy these units as nodes within Internet of Things architectures, enabling massive networked data capture. Hitherto, considerable attention has been focused on imaging applications of these devices. However, within just the last few years, another possibility has emerged: to use smartphones as a means of capturing spectra, mostly by coupling various classes of fore-optics to these units with data capture achieved using the smartphone camera. These highly novel approaches have the potential to become widely adopted across a broad range of scientific e.g., biomedical, chemical and agricultural application areas. In this review, we detail the exciting recent development of smartphone spectrometer hardware, in addition to covering applications to which these units have been deployed, hitherto. The paper also points forward to the potentially highly influential impacts that such units could have on the sciences in the coming decades.
doi:10.3390/s18010223
Avalanche Breakdown Timing Statistics for Silicon Single Photon Avalanche Diodes
2017
Petticrew, JD and Dimler, SJ and Zhou, X and Morrison, AP and Tan, CH and Ng, JS
CCBY Silicon-based Single Photon Avalanche Diodes (SPADs) are widely used as single photon detectors of visible and near infrared photons. There has however been a lack of models accurately interpreting the physics of impact ionization (the mechanism behind avalanche breakdown) for these devices. In this work, we present a statistical simulation model for silicon SPADs that is capable of predicting breakdown probability, mean time to breakdown and timing jitter. Our model inherently incorporates carriers \& #x0027; dead space due to phonon scattering and allows for non-uniform electric fields. Model validation included avalanche gain, excess noise factor, breakdown voltage, breakdown probability, and timing statistics. Simulating an n on-p and a p-on-n SPAD design using our model, we found that the n-on-p design offers significantly improved mean time to breakdown and timing jitter characteristics. For a breakdown probability of 0.5, mean time to breakdown and timing jitter from the n-on-p design were 3 and 4 times smaller compared to those from the p on n design. The data reported in this paper is available from the ORDA digital repository (DOI: 10.15131/shef.data.4823248).
doi:10.1109/JSTQE.2017.2779834
Low-cost 3D printed 1 nm resolution smartphone sensor-based spectrometer: instrument design and application in ultraviolet spectroscopy
2017
Wilkes, TC and McGonigle, AJS and Willmott, JR and Pering, TD and Cook, JM
**********************
doi:10.1364/OL.42.004323
Ultraviolet Imaging of Volcanic Plumes: A New Paradigm in Volcanology
2017
McGonigle, AJS and Pering, TD and Wilkes, TC and Tamburello, G and D’Aleo, R and Bitetto, M and Aiuppa, A and Willmott, JR
**********************
doi:10.3390/geosciences7030068
Thin Al1−xGaxAs0.56Sb0.44 diodes with extremely weak temperature dependence of avalanche breakdown
2017
Zhou, X and Tan, CH and Zhang, S and Moreno, M and Xie, S and Abdullah, S and Ng, JS
**********************
doi:10.1098/rsos.170071
Thin Al1−xGaxAs0.56Sb0.44 diodes with extremely weak temperature dependence of avalanche breakdown
2017
Zhou, X and Tan, CH and Zhang, S and Moreno, M and Xie, S and Abdullah, S and Ng, JS
**********************
doi:10.1098/rsos.170071
Absorption coefficients in AlGaInP lattice-matched to GaAs
2017
Cheong, JS and Baharuddin, A and Ng, JS and Krysa, AB and David, JPR
© 2017 The AuthorsThe absorption coefficient of AlGaInP lattice-matched to GaAs, across the composition range from AlInP to GaInP has been obtained from photocurrent versus wavelength measurements on seven homo-junction AlGaInP PIN diode structures. Due to the sensitivity of the photocurrent measurement technique, values of absorption down to 100 cm−1 have been determined close to the band-gap. From these, the bandgaps in this material system were extracted across the composition range and these corroborate data in the literature that shows the band-gap becoming indirect when the aluminium content, x>0.48.
doi:10.1016/j.solmat.2017.01.042
Laser diode area melting for high speed additive manufacturing of metallic components
2017
Zavala-Arredondo, M and Boone, N and Willmott, J and Childs, DTD and Ivanov, P and Groom, KM and Mumtaz, K
**********************
doi:10.1016/j.matdes.2016.12.095
Proton radiation effect on InAs avalanche photodiodes
2017
Zhou, X and White, B and Meng, X and Zhang, S and Gutierrez, M and Robbins, M and Rojas, LG and Nelms, N and Tan, CH and Ng, JS
**********************
doi:10.1364/OE.25.002818
A Low-Cost Smartphone Sensor-Based UV Camera for Volcanic SO2 Emission Measurements
2017
Wilkes, T and Pering, T and McGonigle, A and Tamburello, G and Willmott, J
**********************
doi:10.3390/rs9010027
Ultraviolet Imaging with Low Cost Smartphone Sensors: Development and Application of a Raspberry Pi-Based UV Camera
2016
Wilkes, TC and McGonigle, AJS and Pering, TD and Taggart, AJ and White, BS and Bryant, RG and Willmott, JR
Here, we report, for what we believe to be the first time, on the modification of a low cost sensor, designed for the smartphone camera market, to develop an ultraviolet (UV) camera system. This was achieved via adaptation of Raspberry Pi cameras, which are based on back-illuminated complementary metal-oxide semiconductor (CMOS) sensors, and we demonstrated the utility of these devices for applications at wavelengths as low as 310 nm, by remotely sensing power station smokestack emissions in this spectral region. Given the very low cost of these units, ≈ USD 25, they are suitable for widespread proliferation in a variety of UV imaging applications, e.g., in atmospheric science, volcanology, forensics and surface smoothness measurements.
doi:10.3390/s16101649
InGaAs/AlGaAsSb avalanche photodiode with high gain - bandwidth product
2016
Xie, S and Zhou, X and Zhang, S and Thomson, DJ and Chen, X and Reed, GT and Ng, JS and Tan, CH
Increasing reliance on the Internet places greater and greater demands for high -speed optical communication systems. Increasing their data transfer rate allows more data to be transferred over existing links. With optical receivers being essential to all optical links, bandwidth performance of key components in receivers, such as avalanche photodiodes (APDs), must be improved. The APDs rely on In0.53Ga0.47As (grown lattice-matched to InP substrates) to efficiently absorb and detect the optical signals with 1310 or 1550 nm wavelength
doi:10.1364/OE.24.024242
Thermal territories of the abdomen after caesarean section birth: Infrared thermography and analysis
2016
Childs, C and Siraj, MR and Fair, FJ and Selvan, AN and Soltani, H and Wilmott, J and Farrell, T
© 2016 MA Healthcare Ltd.Objective: To develop and refine qualitative mapping and quantitative analysis techniques to define 'thermal territories' of the post-partum abdomen, the caesarean section site and the infected surgical wound. In addition to explore women's perspectives on thermal imaging and acceptability as a method for infection screening. Method: Prospective feasibility study undertaken at a large University teaching hospital, Sheffield, UK. Infrared thermal imaging of the abdomen was undertaken at the bedside on the first two days after elective caesarean section. Target recruitment: six women in each of three body mass index (BMI) categories (normal, 18.5-24.9 kg/m2; overweight 25-29.9 kg/m2; obese ≥30 kg/m2). Additionally women presenting to the ward with wound infection were eligible for inclusion in the study. Perspectives on the use of thermal imaging and its practicality were also explored via semi-structured interviews and analysed using thematic content analysis. Results: We recruited 20 women who had all undergone caesarean section. From the booking BMI, eight women were obese (including two women with infected wounds), seven women were overweight and five women had a normal BMI. Temperature (oC) profiling and pixel clustering segmentation (hierarchical clustering-based segmentation, HCS) revealed characteristic features of thermal territories between scar and adjacent regions. Differences in scar thermal intensity profiles exist between healthy scars and infected wounds; features that have potential for wound surveillance. The maximum temperature differences (ΔT) between healthy skin and the wound site exceed 2°C in women with established wound infection. At day two, two women had a scar thermogram with features observed in the 'infected' wound thermogram. Conclusion: Thermal imaging at early and later times after caesarean birth is feasible and acceptable. Women reported potential benefits of the technique for future wound infection screening. Thermal intensity profiling and HCS for pixel cluster dissimilarity between scar and adjacent healthy skin has potential as a method for the development of techniques targeted to early infection surveillance in women after caesarean section. Declaration of interest: All the authors confirm that there is no conflict of interest in the design, conduct and presentation of the research.
doi:10.12968/jowc.2016.25.9.499
Avalanche breakdown characteristics of Al1-xGaxAs0.56Sb0.44 quaternary alloys
2016
Zhou, X and Zhang, S and David, J and Ng, JS and Tan, CH
Avalanche breakdown characteristics are essenti
doi:10.1109/LPT.2016.2601651
Potential for improved radiation thermometry measurement uncertainty through implementing a primary scale in an industrial laboratory
2016
Willmott, JR and Lowe, D and Broughton, M and White, BS and Machin, G
A primary temperature scale requires realising a unit in terms of its definition. For hi
doi:10.1088/0957-0233/27/9/094002
Guest Editorial: Selected Papers from the 29th Semiconductor and Integrated OptoElectronics (SIOE), 2015
2016
Tan, PCH
© 2016 IEEE. The effect of surface passivation on the etched-mesa InAs diodes was investigated by carrying out the fabrication and passivation of InAs diodes. Extensive and detailed current-voltage characterization was done to determine the most suitable type of insulating material for the surface passivation. SU-8, silicon nitride, silicon dioxide and B-staged Bisbenzocyclobutene were used for the purpose of minimizing the conductivity of the etched mesa surface of InAs diodes. The forward- and reverse-biased characteristics of InAs diodes were measured at room temperature and 77 K in order to carefully investigate the effect of different surface passivation schemes. The results of this work categorically indicated that SU-8 is the most effective surface passivation material for InAs diodes, whereas silicon nitride and silicon dioxide have contributed to an even higher surface leakage current. Furthermore, SU-8 passivated InAs diodes were more sustainable to high bias voltages and its robustness increases the opportunity of its utilization for practical applications such as infrared imaging.
doi:10.1049/iet-opt.2015.0132
Al0.52In0.48P avalanche photodiodes for soft X-ray spectroscopy
2016
Auckloo, A and Cheong, JS and Meng, X and Tan,, CH and Ng, JS and Krysa, AB and Tozer, RC and David, JPR
**********************
doi:10.1088/1748-0221/11/03/P03021
Picosecond laser ranging at wavelengths up to 2.4 μm using an InAs avalanche photodiode
2016
Buller, GS and Butera, S and Sandall, I and Vines, P and Tan, CH
**********************
doi:10.1049/el.2015.3995
InGaAs/InAlAs single photon avalanche diode for 1550 nm photons
2016
Meng, X and Xie, S and Zhou, X and Calandri, N and Sanzaro, M and Tosi, A and Tan, CH and Ng, JS
**********************
doi:10.1098/rsos.150584
Temperature dependent characterization of gallium arsenide X-ray mesa p-i-n photodiodes
2016
Lioliou, G and Meng, X and Ng, JS and Barnett, AM
**********************
doi:10.1063/1.4944892
Al0.52In0.48P avalanche photodiodes for soft X-ray spectroscopy
2016
Auckloo, A and Cheong, JS and Meng, X and Tan,, CH and Ng, JS and Krysa, AB and Tozer, RC and David, JPR
**********************
doi:10.1088/1748-0221/11/03/P03021
InGaAs/InAlAs single photon avalanche diode for 1550 nm photons
2016
Meng, X and Xie, S and Zhou, X and Calandri, N and Sanzaro, M and Tosi, A and Tan, CH and Ng, JS
**********************
doi:10.1098/rsos.150584
Characterization of gallium arsenide X-ray mesa p-i-n photodiodes at room temperature
2016
Lioliou, G and Meng, X and Ng, JS and Barnett, AM
**********************
doi:10.1016/j.nima.2015.12.030
Temperature dependence of avalanche gain in Al0.85Ga0.15As0.56Sb0.44 APD
2016
Xie, S and Zhou, X and Zhang, S and Ng, JS and Tan, CH and IEEE
**********************
doi:10.1109/JLT.2016.2531278
Avalanche Noise in Al 0.52 In 0.48 P Diodes
2016
Qiao, L and Cheong, JS and Ong, JSL and Ng, JS and Krysa, AB and Green, JE and David, JPR
**********************
doi:10.1109/LPT.2015.2499545
InAs avalanche photodiodes as X-ray detectors
2015
Meng, X and Zhou, X and Zhang, S and Lees, J and Tan, CH and Ng, JS
**********************
doi:10.1088/1748-0221/10/10/P10030
InAs avalanche photodiodes as X-ray detectors
2015
Meng, X and Zhou, X and Zhang, S and Lees, J and Tan, CH and Ng, JS
**********************
doi:10.1088/1748-0221/10/10/P10030
Determination of absorption coefficients in AlInP lattice matched to GaAs
2015
Cheong, JS and Ng, JS and Krysa, AB and Ong, JSL and David, JPR
**********************
doi:10.1088/0022-3727/48/40/405101
Improved radiation thermometry measurement uncertainty through implementing a primary scale in an industrial laboratory
2015
Willmott, JR and Lowe, D and Broughton, M and White, BS and MacHin, G
**********************
doi:10.1051/metrology/20150015004
