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Solid-state room-temperature masers - with Dr Jonathan Breeze, Imperial College

Image: Dr Jonathan Breeze
Dr Jonathan Breeze

Date: 7 November 2018   Time: 15:00 - 16:00

Abstract and speaker bio below (Tea, coffee, & biscuits provided).

Abstract:
The solid-state masers, invented in the 1950s, had a much less impressive career than its younger sibling the laser, mainly due to its dependence on cryogenic refrigeration and high-vacuum systems. Despite this, masers found niche application in deep-space communications and radio astronomy due to their unparalleled performance as low-noise amplifiers and oscillators. In 2012, the first room-temperature solid-state maser was demonstrated, exploiting an ensemble of inverted triplet states in photo-excited pentacene molecules doped into a p-terphenyl host [1]. Since then, this new class of maser has been miniaturized [2], characterized on nanosecond timescales [3] and shown to exhibit Rabi oscillations and normal-mode splitting, hallmarks of the strong-coupling regime of cavity quantum electrodynamics [4]. Unfortunately, the p-terphenyl host is volatile, has very poor thermal properties and unfavourable triplet sublevel decay rates – so that only pulsed operation lasting less than a millisecond has been observed to date. Alternative inorganic materials containing spin-polarizable defects such as diamond nitrogen-vacancy (NV) centres and [5,6] and vacancies in silicon carbide [7] have been proposed due to their slow spin-lattice relaxation and spin dephasing rates. These materials have the additional advantage of excellent thermal and mechanical properties.

In this seminar, I will discuss how the organic pentacene solid-state room-temperature maser came about, its subsequent development and how the quest for continuous operation naturally led towards diamond and nitrogen-vacancy centres. I will report on the recently reported continuous-wave room-temperature maser based on optically pumped charged nitrogen-vacancy (NV) defect centres in diamond [8]. I will also discuss prospects for the macroscopic quantum (Dicke) states supported by the maser [9].

[1] M. Oxborrow, J. D. Breeze, N. Alford, Nature, 488, pp. 353–356 (2012)?
[2] J. Breeze et al, Nature Communications, 6 (2015)
[3] E. Salvadori, J.D. Breeze et al, Scientific Reports, 7, 41836 (2017)
[4] J.D. Breeze et al, npj Quantum Information, 3, 40 (2017)
[5] J.H.N Loubser and J A van Wyk, Diamond Research, pp. 11-14, (1977)
[6] L. Jin et al, Nature Communications, 6 (2015)
[7] H. Kraus et al, Nature Physics, 10, pp. 157–162 (2014)
[8] J.D. Breeze et al, Nature, 555, pp. 493–496 (2018)
[9] R.-B. Liu, Nature News & Views, 555 (2018)



Speaker bio:
Room-temperature masers are the main focus of Jonathan's current research activities, but he is also active in the fields of theory and simulation of materials, electromagnetic fields and their interaction.

Jonathan studied Astrophysics at Leeds University, then worked at the National Physical Laboratory (NPL) in the Quantum Metrology division, before joining Matra-Marconi Space Systems and British-Aerospace Space Systems (now Airbus Space & Defence) as a Microwave Design Engineer.

He worked on a number of satellite programs as Responsible Engineer for passive microwave payloads and also conducted research into state-of-the-art passive microwave components: using materials such as high temperature superconductors (HTS) and advanced microwave ceramic dielectrics.

He returned to academia to join Prof. Neil Alford's group where he conducted fundamental research into microwave dielectric ceramics, culminating in a PhD on the theory and experiment of microwave losses in single-crystal ceramics.

He developed a microwave photonic-crystal cavity with record Q-factor, that led to the research in room-temperature maser. This resulted in the first demonstration of a pulsed room-temperature maser using an optically excited single-crystal of pentacene-doped para-terphenyl. Further research led to the observation of strong-coupling in masers and the demonstration of a continuously-operating maser using optically-pumped diamond containing nitrogen-vacancy defects.

Location:  Bancroft Road Teaching Rooms 3.02, Mile End Campus, Queen Mary University of London
Contact:  Dr Flynn Castles
Email:  f.castles@qmul.ac.uk