Dr. Lewis S. Fleming Profile

Dr. Lewis S. Fleming

PhD Student at Univ of The West of Scotland

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Publications (4)

Proceedings Article | 24 June 2024 Poster + Paper

Pulsed DC sputter deposited hydrogenated carbon: an alternative durable infrared optical thin film material

S. Ahmadzadeh, L. Fleming, D. Gibson

Proceedings Volume 13020, 1302011 (2024) https://doi.org/10.1117/12.3023594

KEYWORDS: Hydrogen, Carbon, Thin films, Infrared radiation, Coating stress, Transmittance, Sputter deposition, Infrared sensors, Infrared materials

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Proceedings Article | 24 June 2024 Presentation + Paper

Microwave plasma assisted sputtering of a combined Ta2O5/SiO2 and a-Si:H/SiO2 two stack optical coating design concept for gravitational wave detectors

Connor Lindsay, Carlos García Nuñez, Lewis Fleming, Jonathan Pomfret, Kirstin Saunders, Sam Ahmadzadeh, Simon Tait, Stuart Reid, Iain Martin, Des Gibson

Proceedings Volume 13020, 130200J (2024) https://doi.org/10.1117/12.3022968

KEYWORDS: Coating, Amorphous silicon, Absorption, Microwave radiation, Sputter deposition, Optical properties

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Proceedings Article | 20 June 2024 Presentation + Paper

Light powered battery-less non-dispersive infrared sensor for methane gas detection

Lewis Fleming, Sam Ahmadzadeh, Jonathan Pomfret, Ewan Waddell, Greg McGann, David Hutson, Emma Keel, Matthias Kauer, Matthieu Bellanger, Ian Brinkley, Des Gibson

Proceedings Volume 12999, 129990L (2024) https://doi.org/10.1117/12.3022146

KEYWORDS: Methane, Sensors, Environmental sensing, Solar cells, Gas sensors, Vacuum chambers, Relative humidity, Climatology, Light emitting diodes, Infrared sensors

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Methane is a significant contributor to global warming so reducing methane emissions, particularly from oil and gas operations, is among the most cost effective, impactful actions governments can take to achieve climate goals. Preventing methane leakage impacts economic productivity and worker safety too. Large-site leak detection requires reliable cost-effective distributed sensors.

Methane leakage is also an issue for several other industries. However, hard wiring is not practical or cost effective and battery power is unacceptable due to the need for regular changes requiring engineers working in hazardous areas at great expense. The sustainability challenge of additional travel associated with device maintenance and disposal of used batteries in the millions is also environmentally unacceptable. Worker safety monitoring with lower-cost portable methane detectors requires bulky, rechargeable battery-powered devices that the industry is seeking to avoid for operational and environmental reasons. Various low-cost sensor technologies have been applied to methane sensing (catalytic, optical - non-dispersive infrared (NDIR), semiconducting metal oxide and electrochemical) with catalytic/pellistor sensors formerly being dominant but in recent years replaced by NDIR sensors overcoming issues of accuracy, susceptibility to poisoning, short lifetimes, power consumption, recalibration and requirement for oxygen presence. It also has the advantage of being a fail-to-safe technology.

In this work, we present an optical NDIR gas sensor that uses a fast-response semiconductor light source/detector optopair operating at <1 mW power consumption, compatible with powering from photovoltaic based energy harvesting. This is a step change from current state-of-the-art gas sensor technologies and orders of magnitude lower than filament/thermopile based detectors. Fabrication of the sensor is discussed, including; semiconductor mid-IR optopair fabrication, mid-IR optical interference filter deposition and injection molded 2-mirror parabolic reflector optical system preparation. Sensor response to methane is discussed and light harvesting operation is demonstrated, enabling compatibility with wireless distributed methane sensor networks.

Proceedings Article | 24 February 2017 Paper

One-dimensional photonic crystals for eliminating cross-talk in mid-IR photonics-based respiratory gas sensing

L. Fleming, D. Gibson, S. Song, D. Hutson, S. Reid, C. MacGregor, C. Clark

Proceedings Volume 10103, 1010318 (2017) https://doi.org/10.1117/12.2247851

KEYWORDS: Optical filters, Sensors, Absorption, Gas sensors, Carbon monoxide, Light emitting diodes, Transmittance, Photodiodes, Photonic crystals, Optical testing

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