Figure 3.

Some examples of different optical microcavities. (a) Vertical optical ring resonators. Adapted from [46]; (b) Knot resonators; (c) Microbubble resonators. Reprinted from [47], with the permission of AIP Publishing; (d) Polystyrene microsphere resonators. These resonators are an inexpensive way to perform many experiments in parallel. Reprinted from [48], with the permission of AIP Publishing; (e) Crystalline CaF₂ cavities. The resonator is shown in the area between the white brackets and is ~5.5 mm in diameter. Reprinted from [54]; (f) Microdisk resonators; and (g) Liquid droplet resonators. The inset is of a liquid paraffin oil drop. Adapted from [44]. Copyright Wiley-VCH Verlag GmbH & Co. KGaA.