[1] Univ Surrey, Adv Technol Inst, Guildford GU2 7XH, Surrey, England
[2] Univ Surrey, Dept Phys, Guildford GU2 7XH, Surrey, England
[3] Nanyang Technol Univ, Sch Elect & Elect Engn, Singapore 639798, Singapore
[4] King Abdullah Univ Sci & Technol, Elect & Math Sci & Engn Div, Thuwal 23955, Saudi Arabia