Terahertz Wave Detection and Imaging with a Hot Rydberg Vapour

Abstract

This thesis investigates the resonant interaction between Rydberg atoms in a hot caesium vapour and terahertz frequency electromagnetic fields, and explores hyperfine quantum beats modified by driving an excited state transition in an inverted ladder scheme. The 21P 3/2 caesium Rydberg atoms are excited using a three-step ladder scheme and we use a terahertz field resonant with the 21P 3/2 → 21S 1/2 transition (0.634 THz), to measure Autler-Townes splitting of a 3-photon Rydberg electromagnetically induced transparency (EIT) feature. The Autler-Townes splitting allows us to infer the terahertz electric field amplitude, and we show a worked example measurement of a low-amplitude electric field, yielding 25 ± 5 mVcm −1. By driving an off-resonant Raman transition which combines the laser and terahertz fields, we restrict the Rydberg excitation to areas of the caesium vapour where the laser and terahertz fields spatially overlap. We show that the terahertz field intensity is proportional I would like to express my heartfelt thanks to everyone who has helped me through the years of my PhD study. Foremost, it has been a privilege to have the guidance of my supervisor, Kevin Weatherill-thank you for your patience, support and confidence. Thank you also to my second supervisor, Charles Adams, for your ideas and suggestions in our weekly meetings. Any of the work would have been impossible without a super team of people. Thank you to Massayuki, Natalia, Patrick, Hadrien and, in particular, Nick, to whom I am grateful for physical insight, laboratory guerrilla tactics and advice for life. Good luck to Lucy, who will be continuing work on the project, and to Massayuki and Natalia who are embarking in new employment. I would also like to thank Mike Tarbutt, Claudio Balocco and Andrew Gallant for loaning us vital equipment and offering helpful advice. Thank you to Ifan Hughes for introducing me to Durham as a summer student. I have been immensely happy working within the AtMol group-thank you to everyone who has made my time so enjoyable. In particular thank you to Rob, James, Christoph, Dan, Pete, Mark and Danny for board games and Dani, Tommy and Nick for lunchtime runs. Thank you Alistair for all the ready-salted crisps(!), and the members of fAtMol for weekly cake and physics chat. Finally I would like to thank my family, Sally, Geof and David, for their support and for passing me their interest in science.