1 University of Strathclyde, Strathclyde Institute of Pharmacy and Biomedical Sciences, Centre for Biophotonics, Glasgow G4 ORE, United KingdombUniversity of Sussex, School of Engineering and Informatics, Brighton BN1 9QJ, United Kingdom.
2 University of Sussex, School of Engineering and Informatics, Brighton BN1 9QJ, United Kingdom.
3 University of Strathclyde, Department of Physics, Glasgow G1 1XJ, United Kingdom.