[Seminar] ''Impact of mirror shape on Fabry-Pérot optical cavity performance'' by Dr. William Hughes

Speaker: Dr. William Hughes, The University of Southampton

Fabry-Pérot optical cavities are crucial components for quantum technology applications as they can strongly couple quantum emitters to single photons of a directed mode. The need for scalable devices has led to the development of microcavities, which offer small physical footprints and fast interaction timescales. While larger cavities have traditionally had spherical mirrors, microcavity mirror fabrication methods can result in deviations, accidental or deliberate, from a spherical shape.

 This talk will focus on how mirror shape impacts the performance of Fabry-Pérot cavities. After introducing the physics of photon generation in spherical mirror cavities, I will discuss the impact of unintended shape distortions, in particular the common case that the mirror is Gaussian-shaped rather than spherical. We will find that shape distortion exposes the cavity modes to complicated resonant mixing processes which would have severe impacts on experimental devices. We will then examine how non-spherical mirror shape could instead improve cavity performance, discussing our 'retroreflective' method to find the optimum mirror shape, which unveils how mirror shaping can overcome limitations imposed by spherical mirrors. I finally detail how even simple shaping could offer near order-of-magnitude cooperativity enhancement for cavities in the convenient plano-concave configuration.