External seminar archive:

Dielectric nanocavities for enhanced Purcell effect and strong directionality

3 July 2019
Dr Riccardo Sapienza, Imperial College of Science and Technology

In this talk I will discuss our experiments with dielectric nanocavities for single photon manipulation.

I will report parabolic antennas surrounding an individual quantum dot as a source of collimated single photons, which can then be easily extracted and manipulated. These are fabricated by direct laser writing over a single quantum dot localised by confocal microscopy.

The parabolic antenna provides one of the largest reported experimental directivities (D = 106) and the lowest beam divergences (Θ1/2 = 13.5°) and a broadband operation over all of the visible and near-infrared range together with extraction efficiency of more than 96%, offering a practical advantage for quantum technological applications.

Moreover, I will discuss a design concept for tailoring the local density of optical states (LDOS) in dielectric nanostructures, based on the phase distribution of the scattered optical fields induced by point-like emitters. I will report dielectric Mie resonators with up to 1000 Purcell enhancements.

The coherent design provides a powerful tool for high-performance dielectric resonators, and affords fundamental insights into light-matter coupling at the nanoscale.


  1. S. Morozov, M. Gaio, S. A. Maier, R. Sapienza, A metal-dielectric parabolic antenna to direct single photons, Nano Letters, 18, 3068 (2018).

  2. S. Mignuzzi, S. Vezzoli, S. A. R. Horsley, W. L. Barnes, S. A. Maier, R. Sapienza, Nanoscale design of the local density of optical states, Nano Letters, ArXiv/1809.05514 (2019).