Supervisors:

Pascal Del'Haye

Mark Oxborrow

MODE SPECTROSCOPY OF COUNTER-PROPAGATING LIGHT IN MICRORESONATORS
Whispering gallery mode resonators are circular structures that have the ability to guide light around their walls in optical mode areas of the order of μm². In combination to their high Quality factors (~ 10⁸), they have a low threshold power for third order nonlinear effects taking place.

A strong beam changes the refractive index of the medium as experienced both by itself (self-phase modulation), but also twice as much by other overlapping beams (cross-phase modulation) circulating the resonator. Even though self- and cross-phase modulations are well known third order effects, they have yet to be observed as direct resonance shift in microresonators; They are often negligible compared to thermal resonance frequency shifts, caused by the strong beam warming up the resonator enough for it to expand, leading to a change in optical path and hence a resonance frequency shift. Like all third order nonlinear effects, self- and cross-phase modulations are dependent on the intensity of the beam.