Abstract:
Optical frequency combs are an exciting area of research with applications in Spectroscopy, optical sensing and telecommunications and in addition they have revolutionized the optical clock. Octave spanning frequency combs have been recently demonstrated using Microresonators. Made from a transparent material, these devices have spherical or toroidal shape and are typically between tens and hundreds of micrometers in size. The light is coupled in through a prism or fibre taper using evanescent wave coupling and circulates the cavity in highly confined whispering gallery modes. Due to the small modal cross section and long photon lifetimes there is a low threshold for nonlinear interaction. Researchers envisage these devices being used for low power microchip scale frequency comb sources in photonic devices. There has been much work on the experimental side of Microresonators, but little in the way of modelling, in particular the interesting nonlinear optical properties of these devices. This thesis describes a new method for modelling microresonator frequency combs, which reduces computational time compared to existing approaches. Two numerical simulation methods, the Newton-Raphson and split step Fourier, are chosen for their suitability to the study of steady state and dynamic regimes respectively. Simulations were performed using code written in MATLAB. We were able to simulate frequency combs with spans exceeding one octave of the spectral domain and containing over 1000 spectral modes, more than twice the number of modes than in any previously published study. The comb spectra were found to be in good agreement with experimental combs published by other researchers. Finally, some inroads were made to a numerical study of comb versatility.
