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2024

Dwivedi, Utkarsh and Donnachie, Mark and Ilke, Metin and Bauer, Ralf and Lengden, Michael (2024) Performance comparison of 3D printed photoacoustic gas sensors and a commercial quartz enhanced photoacoustic spectrometer. IEEE Sensors Journal, 24 (1). pp. 943-951. ISSN 1530-437X

2023

Zhang, Rui and Xia, Jiangnan and McCann, Hugh and Liu, Chang and Ahmed, Ihab and Pourkashanian, Mohamed and Gough, Andrew and Armstrong, Ian and Lengden, Michael and Johnstone, Walter; (2023) Miniature modular sensor for chemical species tomography with enhanced spatial resolution. In: 2023 IEEE International Conference on Imaging Systems and Techniques (IST). IEEE International Workshop on Imaging Systems and Techniques (IST) . IEEE, DNK. ISBN 9798350330830

Zhang, Rui and Xia, Jiangnan and Ahmed, Ihab and Gough, Andrew and Armstrong, Ian and Upadhyay, Abhishek and Fu, Yalei and Enemali, Godwin and Lengden, Michael and Johnstone, Walter and Wright, Paul and Ozanyan, Krikor and Pourkashanian, Mohamed and McCann, Hugh and Liu, Chang (2023) A fast sensor for non-intrusive measurement of concentration and temperature in turbine exhaust. Sensors and Actuators B: Chemical, 396. 134500. ISSN 0925-4005

Fu, Yalei and Zhang, Rui and Xia, Jiangnan and Gough, Andrew and Clark, Stuart and Upadhyay, Abhishek and Enemali, Godwin and Armstrong, Ian and Ahmed, Ihab and Pourkashanian, Mohamed and Wright, Paul and Ozanyan, Krikor and Lengden, Michael and Johnstone, Walter and Polydorides, Nick and McCann, Hugh and Liu, Chang (2023) Hybrid model-driven spectroscopic network for rapid retrieval of turbine exhaust temperature. IEEE Transactions on Instrumentation and Measurement, 72. 2531710. ISSN 1557-9662

Flockhart, Gordon M. H. and Bauer, Ralf and Lengden, Michael; McKee, Michael and Hagan, David J., eds. (2023) Photonic systems integration for postgraduate students in the Centre for Doctoral Training in Applied Photonics. In: Proceedings Volume 12723, Seventeenth Conference on Education and Training in Optics and Photonics: ETOP 2023. SPIE, USA, pp. 1-10. ISBN 9781510666719

2022

Upadhyay, Abhishek and Lengden, Michael and Enemali, Godwin and Stewart, George and Johnstone, Walter and Wilson, David and Humphries, Gordon and Benoy, Thomas and Black, John and Chighine, Andrea and Fisher, Edward and Zhang, Rui and Liu, Chang and Polydorides, Nick and Tsekenis, Alex and Wright, Paul and Kliment, Joshua and Nilsson, Johan and Feng, Yutong and Archilla, Victor and Rodriguez-Carmona, Javier and Sanchez-Valdepenas, Jesus and Beltran, Marta and Polo, Valentin and Armstrong, Ian and Mauchline, Iain and Walsh, Douglas and Johnson, Mark and Bauldreay, Joanna and McCann, Hugh (2022) Tomographic imaging of carbon dioxide in the exhaust plume of large commercial aero-engines. Applied Optics, 61 (28). pp. 8540-8552. ISSN 1559-128X

Otti, P. and Humphries, G.S. and Hu, Y. and Lengden, M. and Burns, I.S. (2022) Measurement of acetylene concentration in laminar flat flames by diode laser cavity ring-down spectroscopy. Applied Physics B: Lasers and Optics, 128 (9). 165. ISSN 0946-2171

Fu, Yalei and Zhang, Rui and Enemali, Godwin and Upadhyay, Abhishek and Lengden, Michael and Liu, Chang; (2022) Convolutional neural network aided chemical species tomography for dynamic temperature imaging. In: 2022 IEEE International Instrumentation and Measurement Technology Conference (I2MTC). IEEE International Instrumentation and Measurement Technology Conference . IEEE, Piscataway, NJ, pp. 1-5. ISBN 9781665483605

2020

Ilke, Metin and Bauer, Ralf and Lengden, Michael (2020) A calibration-free methodology for resonantly enhanced photoacoustic spectroscopy using quantum cascade lasers. IEEE Sensors Journal, 20 (18). pp. 10530-10538. ISSN 1530-437X

Fisher, Edward M. D. and Tsekenis, Stylianos-Alexios and Yang, Yunjie and Chighine, A. and Liu, Cheng and Polydorides, Nick and Wright, P. and Kliment, J. and Ozanyan, K. and Benoy, Thomas and Humphries, Gordon and Wilson, David and Lengden, M. and Johnstone, Walter and McCann, Hugh (2020) A custom, high-channel-count data acquisition system for chemical species tomography of aero-jet engine exhaust plumes. IEEE Transactions on Instrumentation and Measurement, 69 (2). pp. 549-558. ISSN 0018-9456

2019

Wilson, David and Phair, John W. and Lengden, Michael (2019) Performance analysis of a novel pyroelectric device for non-dispersive infra-red CO2 detection. IEEE Sensors Journal, 19 (15). pp. 6006-6011. ISSN 1530-437X

Humphries, Gordon S. and Roy, Robert and Black, John D. and Lengden, Michael and Burns, Iain S. (2019) In-situ photoacoustic measurement of soot profiles in laminar flames using a high repetition-rate pulsed fibre laser. Applied Physics B: Lasers and Optics, 125 (4). 60. ISSN 0946-2171

2018

Upadhyay, Abhishek and Lengden, Michael and Wilson, David and Humphries, Gordon Samuel and Crayford, Andrew P. and Pugh, Daniel G. and Johnson, Mark P. and Stewart, George and Johnstone, Walter (2018) A new RAM normalized 1f-WMS technique for the measurement of gas parameters in harsh environments and a comparison with 2f/1f. IEEE Photonics Journal, 10 (6). 6804611. ISSN 1943-0655

Zhang, Congzhe and Yang, Yuanhong and Lin, Yuechuan and Tan, Yanzhen and Lengden, Michael and Humphries, Gordon and Johnstone, Walter and Lut Ho, Hoi and Jin, Wei; (2018) All-optical fiber multi-point photoacoustic spectroscopic gas sensing system. In: Proceedings 26th International Conference on Optical Fiber Sensors. Optical Society of America, CHE. ISBN 9781943580507

Humphries, Gordon S. and Lengden, Michael (2018) Azimuthally excited resonators for photoacoustic spectroscopy. In: Field Laser Applications in Industry and Research (FLAIR) 2018, 2018-09-10 - 2018-09-14.

Archilla, V. and Aragón, G. and Wright, P. and Ozanyan, K. and Black, J. and Polydorides, N. and McCann, H. and Lengden, M. and Burns, I. and Johnstone, W. and Polo, V. and Beltran, M. and Mauchline, I. and Walsh, D. and Johnson, M. (2018) CIDAR : combustion species imaging diagnostics for aero-engine research. In: Aerosol Technology, 2018-06-18 - 2018-06-20.

Archilla, V. and Aragón, G. and Wright, P. and Ozanyan, K. and Black, J. and Lengden, M. and Burns, I. and Johnstone, W. and Polo, V. and Beltran, M. and Johnson, M. (2018) CIDAR project - development of a non-intrusive capability for aircraft engine measurements. In: Aerosol Technology, 2018-06-18 - 2018-06-20.

2017

Humphries, Gordon S. and Bauer, Ralf and Lengden, Michael (2017) Performance of a azimuthally excited 3D-printed resonator for multi-pass spectroscopic applications. In: IEEE SENSORS 2017, 2017-10-29 - 2017-11-01, Scottish Exhibition and Conference Centre.

Polydorides, Nick and Tsekenis, Alex and Fisher, Edward and Chigine, Andrea and McCann, Hugh and Dimiccoli, Luca and Wright, Paul and Lengden, Michael and Benoy, Thomas and Wilson, David and Humphries, Gordon and Johnstone, Walter (2017) Constrained models for optical absorption tomography. Applied Optics, 57 (7). B1-B9. ISSN 1559-128X

Benoy, Thomas and Wilson, David and Lengden, Michael and Armstrong, Ian and Stewart, George and Johnstone, Walter (2017) Measurement of CO2 concentration and temperature in an aero engine exhaust plume using wavelength modulation spectroscopy. IEEE Sensors Journal, 17 (19). pp. 6409-6417. ISSN 1530-437X

Upadhyay, Abhishek and Wilson, David and Lengden, Michael and Chakraborty, Arup L. and Stewart, George and Johnstone, Walter (2017) Calibration-free WMS using a cw-DFB-QCL, a VCSEL, and an edge-emitting DFB laser with in-situ real-time laser parameter characterization. IEEE Photonics Journal, 9 (2). 6801217. ISSN 1943-0655

2016

Bauer, Ralf and Flockhart, Gordon M. H. and Johnstone, Walter and Lengden, Michael; (2016) Trace gas sensing using DFB laser and QCL with miniaturized 3D-printed photoacoustic gas cells. In: International Conference on Fibre Optics and Photonics 2016. Optical Society of America, IND. ISBN 978-1-943580-22-4

Wilson, David and Humphries, Gordon Samuel and Benoy, Thomas and Lengden, Michael and Johnstone, Walter and Tsekenis, Alex and Fisher, Edward and Chigine, Andrea and McCann, Hugh and Feng, Yutong and Nilsson, Johan and Wright, Paul and McCormick, David and Ozanyan, Krikor and Archilla Prat, Victor and Johnson, Mark and Black, John (2016) Working towards cleaner air travel : the technology behind the FLITES project. In: FLAIR 2016 - Field Laser Applications in Industry and Research, 2016-09-12 - 2016-09-16.

Benoy, Thomas and Lengden, Michael and Stewart, George and Johnstone, Walter (2016) Recovery of absorption line shapes with correction for the wavelength modulation characteristics of DFB lasers. IEEE Photonics Journal, 8 (3). 1501717. ISSN 1943-0655

Tsekenis, Stylianos and Wilson, David and Lengden, Michael and Hyvonen, Jari and Leinonen, Jukka and Shah, Ashish and Andersson, Oivind and McCann, Hugh (2016) Towards in-cylinder chemical species tomography on large-bore IC engines with pre-chamber. Flow Measurement and Instrumentation. ISSN 1873-6998

Bain, James and Lengden, Michael and Stewart, George and Johnstone, Walter (2016) Recovery of absolute absorption line shapes in tunable diode laser spectroscopy using external amplitude modulation with balanced detection. IEEE Sensors Journal, 16 (3). pp. 675-680. ISSN 1530-437X

Humphries, Gordon S. and Burns, Iain S. and Lengden, Michael (2016) Application of continuous-wave cavity ring-down spectroscopy to laminar flames. IEEE Photonics Journal, 8 (1). 3900110. ISSN 1943-0655

2015

Bauer, Ralf and Legg, Thomas and Mitchell, David and Flockhart, Gordon M. H. and Stewart, George and Johnstone, Walter and Lengden, Michael (2015) Miniaturized photoacoustic trace gas sensing using a raman fiber amplifier. Journal of Lightwave Technology, 33 (18). pp. 3773-3780. ISSN 0733-8724

Chighine, Andrea and Fisher, Edward and Wilson, David and Lengden, Michael and Johnstone, Walter and McCann, Hugh; (2015) An FPGA-based lock-in detection system to enable chemical species tomography using TDLAS. In: 2015 IEEE International Conference on Imaging Systems and Techniques (IST). IEEE, Piscataway, NJ, pp. 1-5. ISBN 9781479986330

Lengden, Michael and Bauer, Ralf and Johnstone, Walter (2015) Gas concentration measurements using photoacoustic sensors for industrial solid oxide fuel cell process control. In: ECS Conference on Electrochemical Energy Conversion & Storage with SOFC X1V, 2015-06-26 - 2015-07-31.

Lengden, Michael and Wilson, David and Armstrong, Ian and Benoy, Thomas and Johnstone, Walter (2015) Fibre laser imaging of gas turbine exhaust species – a review of CO2 aero engine imaging. In: Advanced Photonics, 2015-06-27 - 2015-07-01.

Bauer, Ralf M. and Wilson, David and Johnstone, Walter and Lengden, Michael (2015) MIR photoacoustic trace gas sensing using a miniaturized 3D printed gas cell. In: Advanced Photonics, 2015-06-27 - 2015-07-01.

Humphries, G. S. and Dunn, J. and Hossain, M. M. and Lengden, M. and Burns, I. S. and Black, J. D. (2015) A simple photoacoustic method for the in situ study of soot distribution in flames. Applied Physics B: Lasers and Optics, 119 (4). pp. 709-715. ISSN 0946-2171

Wright, Paul and McCormick, David and Ozanyan, Krikor and Johnson, Mark and Black, John and Fisher, Edward and Chighine, Andrea and Polydorides, Nick and McCann, Hugh and Feng, Yutong and Khan, Khouler and Bastock, Paul and Jia, Fuqiang and Hewak, Dan and Nilsson, Johan and Lengden, Michael and Wilson, David and Armstrong, Ian and Benoy, Thomas and Johnstone, Walter; (2015) Progress towards non-intrusive optical measurement of gas turbine exhaust species distributions. In: Aerospace Conference, 2015 IEEE. IEEE, USA, pp. 1-14. ISBN 9781479953790

Bauer, Ralf and Wilson, David and Johnstone, Walter and Lengden, Michael; (2015) MIR photoacoustic trace gas sensing using a miniaturized 3D printed gas cell. In: Advanced Photonics 2015, OSA Technical Digest. Optical Society of America. ISBN 978-1-55752-000-5

Humphries, Gordon and Lengden, Michael and Burns, Iain and Black, John; (2015) Novel in-situ optical measurement techniques for combustion applications. In: Advanced Photonics 2015, OSA Technical Digest. Optical Society of America, USA. ISBN 978-1-55752-000-5

2014

Bauer, Ralf and Stewart, George and Johnstone, Walter and Lengden, Michael (2014) Photoacoustic trace gas sensing using a miniature 3D printed gas cell. In: Photon14, 2014-09-01 - 2014-09-04, Imperial College London.

Bauer, Ralf and Stewart, George and Johnstone, Walter and Boyd, Euan and Lengden, Michael (2014) A 3D-printed miniature gas cell for photoacoustic spectroscopy of trace gases. Optics Letters, 39 (16). pp. 4796-4799. ISSN 0146-9592

Feng, Yutong and Nilsson, Johan and Jain, Saurabh and May-Smith, Timothy C. and Sahu, Jayanta K. and Jia, Fuqiang and Benoy, Thomas and Wilson, David and Lengden, Michael and Johnstone, Walter (2014) LD-seeded thulium-doped fibre amplifier for CO2 measurements at 2 µm. In: Europhoton 2014, 2014-08-24 - 2014-08-29.

Humphries, Gordon Samuel and Burns, Iain and Lengden, Michael (2014) Development of a continuous-wave cavity ring down spectrometer for combustion diagnostics. In: FLAIR 2014 - Field Laser Applications in Industry and Research, 2014-05-05 - 2014-05-09.

Wilson, David and Armstrong, Ian and Lengden, Michael and Johnstone, Walter (2014) In-situ measurement of combustion produced CO2 in the 2μm region, within a jet engine exhaust plume. In: FLAIR 2014 - Field Laser Applications in Industry and Research, 2014-05-05 - 2014-05-09.

Benoy, Thomas and Lengden, Michael and Armstrong, Ian and Wilson, David and Stewart, George and Johnstone, Walter (2014) Near IR tunable diode laser spectroscopy for aero engine research. In: FLAIR 2014 - Field Laser Applications in Industry and Research, 2014-05-05 - 2014-05-09.

Bauer, Ralf and Stewart, George and Johnstone, Walter and Lengden, Michael (2014) A miniaturised 3D printed resonant photoacoustic cell for trace gas sensing. In: FLAIR 2014 - Field Laser Applications in Industry and Research, 2014-05-05 - 2014-05-09.

2013

Bain, James and Lengden, Michael and Armstrong, Ian and Stewart, George and Johnstone, Walter (2013) Development of tunable diode laser spectroscopy instrumentation for gas species measurements in harsh environments. In: Applied Industrial Optics: Spectroscopy, Imaging, and Metrology, 2013-06-23 - 2013-06-27, Virginia.

Lengden, Michael and Cunningham, Robert and Johnstone, Walter (2013) Tunable diode laser based concentration measurements of water vapour and methane on a solid oxide fuel cell. Journal of Lightwave Technology, 31 (9). 1354 - 1359. ISSN 0733-8724

2012

Lengden, Michael and Armstrong, Ian and Bain, James and Johnstone, Walter (2012) Measurement of key species in gas turbine engine exhaust plumes. In: Institute of Physics - Delivering Future Combustion Technologies Meeting, 2012-10-23 - 2012-10-23.

Bain, James and Black, John and Lengden, Michael and Johnstone, Walter (2012) Development of tunable diode laser spectroscopy sensor systems for line-of-sight measurement of water vapour in aero engine exhaust plumes. In: PHOTON12, 2011-03-31.

2011

Lengden, Michael and Cunningham, Robert and Johnstone, Walter (2011) Tuneable diode laser gas analyser for methane measurements on a large scale solid oxide fuel cell. Journal of Power Sources, 196 (20). pp. 8406-8408. ISSN 0378-7753

Lengden, Michael and Johnstone, Walter (2011) Gas composition measurements for fundamental research and process control on a 15kW solid oxide fuel cell. In: Field Laser Applications in Industry and Research, 2011-09-13 - 2011-09-17.

Bain, James and Lengden, Michael and Black, John and Johnstone, Walter (2011) Measurement of aeroengine intake gas temperature using TDLS of atmospheric water vapour. In: Field Laser Applications in Industry and Research, 2011-09-13 - 2011-09-17.

Bain, James Roderic Peter and Lengden, Michael and Stewart, George and Black, John and Johnstone, Walter (2011) Development of a TDLS-based ambient water vapour sensor for aeroengine intake temperature determination. In: 8th International Conference on Tunable Diode Laser Spectroscopy, 2011-07-11 - 2011-07-15. (Unpublished)

Lengden, Michael and Johnstone, Walter and Bain, James Roderic Peter and Milne, Laura (2011) High temperature investigations of methane for the calculation of the temperature dependence of spectral parameters. In: 8th International Conference on Tunable Diode Laser Spectroscopy, 2011-07-11 - 2011-07-15. (Unpublished)

Bain, James Roderic Peter and Johnstone, Walter and Ruxton, Keith Crawford and Stewart, George and Lengden, Michael and Duffin, Kevin (2011) Recovery of absolute gas absorption line shapes using tunable diode laser spectroscopy with wavelength modulation - Part 2 : experimental investigation. Journal of Lightwave Technology, 29 (7). pp. 987-996. ISSN 0733-8724

Bain, James and Lengden, Michael and Stewart, George and Johnstone, Walter (2011) Tunable diode laser spectroscopy for process control and diagnostics in industrial systems. In: 2nd Annual SU2P symposium, 2011, 2011-03-28.

2010

Ruxton, Keith C. and Chakraborty, Arup Lal and Johnstone, W. and Lengden, Michael and Stewart, G. and Duffin, K. (2010) Tunable diode laser spectroscopy with wavelength modulation : elimination of residual amplitude modulation in a phasor decomposition approach. Sensors and Actuators B: Chemical, 150 (1). pp. 367-375. ISSN 0925-4005

Lengden, Michael and Johnstone, W. and Cunningham, Robert (2010) In-situ, real time gas composition measurements for SOFC's using laser spectroscopy. In: European Fuel Cell Forum 2010, 2010-06-29 - 2010-07-02. (Unpublished)

Armstrong, I. and Johnstone, W. and Duffin, K. and Lengden, Michael and Chakraborty, Arup Lal and Ruxton, Keith C. (2010) Detection of CH4 in the mid-IR using difference frequency generation with tunable diode laser spectroscopy. Journal of Lightwave Technology, 28 (10). pp. 1435-1442. ISSN 0733-8724

2009

Bain, J.R.P. and Stewart, G. and Duffin, K. and Lengden, M. and Ruxton, K.C. and Johnstone, W. (2009) Recovery of absolute gas absorption lineshapes using TDLS at arbitrary modulation indices. In: UNSPECIFIED.

Bain, J.R.P. and Stewart, G. and Duffin, K. and Lengden, M. and Ruxton, K.C. and Johnstone, W. (2009) Recovery of gas absorption lineshapes using TDLS at arbitrary modulation indices. In: International Conference on Field Laser Applications in Industry and Research, 2009-09-06 - 2009-09-11, Hotel am Badersee.

Lengden, M. and Bain, J.R.P. and Armstrong, I. and Johnstone, W. (2009) Two gas spectrometers for the investigation of gas absorption parameters at elevated temperatures and pressures. In: International Conference on Field Laser Applications in Industry and Research, 2009-09-06 - 2009-09-11, Hotel am Badersee.

Lengden, M. and Johnstone, W. and Bain, J.R.P. and Stewart, G. and Armstrong, I. (2009) Preliminary gas composition investigations at elevated temperatures and pressures using calibration-free tDLS with the residual amplitude modulation technique. In: 7th International Conference on Tunable Diode Laser Spectroscopy, 2009-07-13 - 2009-07-17.

Chakraborty, Arup Lal and Ruxton, Keith C. and Johnstone, W. and Lengden, Michael and Duffin, K. (2009) Elimination of residual amplitude modulation in TDLS-WMS. In: Conference on Lasers and Electro-Optics/ European Quantum Electronics Conference (CLEO Europe/EQEC-2009), 2009-06-14 - 2009-06-19.

Chakraborty, Arup Lal and Ruxton, Keith C. and Johnstone, W. and Lengden, Michael and Duffin, K. (2009) Elimination of residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy using an optical fiber delay line. Optics Express, 17 (12). pp. 9602-9607. ISSN 1094-4087