Quasinormal modes, Purcell factors and corrected Fermi’s golden rule for spontaneous emission decay in coupled loss-gain resonators

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• Stephen Hughes (Queen's University)
• Wednesday 23 June 2021, 14:00-15:00
• https://bham-ac-uk.zoom.us/j/84694385772?pwd=VXZCNVVJdVNQNCtTL2JoOUg3MExidz09.

If you have a question about this talk, please contact Dr Miguel Navarro-Cia.

Zoom Meeting ID: 846 9438 5772

The mechanism of spontaneous emission decay has been hotly debated for decades, ranging from interpretations of radiation reaction, vacuum fluctuations, classical, semiclassical, and purely quantum mechanical. In nanophotonics, it is widely believed that the spontaneous emission decay rate simply scales with the photonic local density of states (LDOS), a result also known as the “photonic golden rule”. Thus, the classical LDOS control spontaneous emission. What then does it mean if the LDOS is negative? This talk will introduce a linear system that indeed yields negative LDOS values for coupled loss-gain resonators. Coupled loss and gain resonators exhibit parity-time (PT) symmetry and exceptional points, and find rich applications in sensing, lasing, and quantum optics. We will present an intuitive and powerful quasinormal mode theory for coupled loss and gain resonators, and demonstrate extremely rich spectral lineshapes and Purcell factors (enhanced spontaneous emission) for coupled loss-gain microdisk cavities. We then point out a fundamental flaw in currently adopted theories of spontaneous emission in such media and present a corrected Fermi’s golden rule, one that requires a fully quantum mechanical description [1].

[1] S. Franke, J. Ren, M. Richter, A. Knorr, and S. Hughes, Fermi’s golden rule for spontaneous emission in absorptive and amplifying media, e-print: arXiv:2102.13015 (2021); Phys Rev Lett, in-press

This talk is part of the Metamaterials and Nanophotonics Group Seminars series.

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