Professor Paul Ewart: Publications

Photo-induced optical activity in phase-change memory materials

Scientific Reports Springer Nature 5 (2015) 8770

Authors:

Konstantin Borisenko, J Shanmugam, Benjamin Williams, Paul Ewart, B Gholipour, DW Hewak, R Hussain, T Jávorfi, G Siligardi, Angus Kirkland

Abstract:

We demonstrate that optical activity in amorphous isotropic thin films of pure Ge2Sb2Te5 and N-doped Ge2Sb2Te5N phase-change memory materials can be induced using rapid photo crystallisation with circularly polarised laser light. The new anisotropic phase transition has been confirmed by circular dichroism measurements. This opens up the possibility of controlled induction of optical activity at the nanosecond time scale for exploitation in a new generation of high-density optical memory, fast chiroptical switches and chiral metamaterials.

Mid-infrared multi-mode absorption spectroscopy, MUMAS, using difference frequency generation

Applied Physics B: Lasers and Optics 118:3 (2015) 343-351

Authors:

H Northern, S O’Hagan, ML Hamilton, P Ewart

Abstract:

Multi-mode absorption spectroscopy of ammonia and methane at 3.3 μm has been demonstrated using a source of multi-mode mid-infrared radiation based on difference frequency generation. Multi-mode radiation at 1.56 μm from a diode-pumped Er:Yb:glass laser was mixed with a single-mode Nd:YAG laser at 1.06 μm in a periodically poled lithium niobate crystal to produce multi-mode radiation in the region of 3.3 μm. Detection, by direct multi-mode absorption, of NH3 and CH4 is reported for each species individually and also simultaneously in mixtures allowing measurements of partial pressures of each species.

Mid-infrared multi-mode absorption spectroscopy, MUMAS, using difference frequency generation

Applied Physics B Springer Nature 118:3 (2015) 343-351

Authors:

Henry Northern, Seamus O’Hagan, Michelle L Hamilton, Paul Ewart

Abstract:

Simultaneous detection of CO2 and CO in engine exhaust using multi-mode absorption spectroscopy, MUMAS

Sensors and Actuators B Chemical Elsevier 198 (2014) 309-315

Authors:

Alexander Thompson, Henry Northern, Benjamin Williams, Michelle Hamilton, Paul Ewart

Multi-species detection using mid-infrared multi-mode absorption spectroscopy, MUMAS

Optics InfoBase Conference Papers (2014)

Authors:

H Northern, S O'Hagan, B Fletcher, P Ewart, CS Kim, M Kim, CD Merritt, WW Bewley, CL Canedy, J Abell, I Vurgaftman, JR Meyer

Abstract:

Multi-mode absorption spectroscopy has been used to detect CH4, NH3 and N2O individually or simultaneously in mixtures using multi-mode radiation generated by difference frequency generation at 3.3 μm or inter-band cascade lasers at 3.7 μm. © 2014 OSA.

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