Multimode Microresonator Optical Frequency Combs

This thesis presents an experimental and theoretical investigation of multi-mode microresonator optical frequency combs. Experimentally, we drive a single microresonator with multiple independent lasers to observe the scattering of a probe field from a soliton frequency comb, as well as study the excitation and control of multiple soliton combs in a single resonator. First, we consider the co-propagation of two driving lasers in the same spatial mode of a Kerr microresonator. Experimentally we observe a soliton-linear wave (LW) interaction and investigate this novel result at different azimuthal mode number separations. Theoretically, we explain the dynamics of the LW interaction as a cascade of four-wave-mixing Bragg scattering events. This allows us to extend the treatment of single-pass Bragg scattering cascades to a resonator context. We find the soliton-LW interaction leads to the formation of a secondary idler comb whose frequency components possess exactly the same line-spacing as, yet are spectrally offset from, the original soliton comb. By adjusting the relative detuning between the two driving lasers; the position of this idler comb can be tuned and optimised. The new frequencies generated by the idler comb provide the possibility for useful, tunable spectral extension of the original soliton comb. Next, we consider the application of two driving lasers to generate two independent soliton combs in the same resonator. We are able to demonstrate this dual micro-comb operation with the two pumps counterpropagating in the same spatial mode, as well as in different spatial modes. Upon combination and measurement on a photodetector, the ‘dual-combs’ beat to yield an RF comb. We experimentally show that by adjusting the azimuthal mode number separations and relative laser detuning; coarse and fine tuning of the RF comb line-spacing is possible. We theoretically explain the coarse tuning via the contributions of dispersion across both azimuthal mode numbers and use of different spatial modes. The fine tuning is a result of differential self-phase modulation experienced by the two soliton combs. We conclude these findings with a proof-of-concept dual-comb spectroscopy demonstration and preliminary tri-comb observation through the addition of a third driving laser.

Name thesis:degree_name

PhD

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Physics

Grantor dc:publisher

ResearchSpace@Auckland

Year dc:date.issued

2024

Author dc:creator

• Qureshi, Pierce Chris

Advisors dc:contributor.advisor

• Murdoch, Stuart
• Erkintalo, Miro
• Coen, Stéphane

Statement dc:rights

• Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Licence dc:rights.uri

• https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm

Handle dc:identifier.uri

https://hdl.handle.net/2292/70413

OAI identifier oai:identifier

oai:researchspace.auckland.ac.nz:2292/70413