On-chip Kerr frequency comb generation and its effects on the application of optical communications

2018-01-30A large number of precisely spaced spectral lines form an optical frequency comb, which enables a wide range of applications including frequency metrology, atomic clocks, precision spectroscopy, and optical communications. In recent years, compact microresonator-based Kerr frequency combs have attracted much attention because of their compactness and high repetition rate. Kerr frequency combs in a low-noise state also have the advantages of high coherence and broadband coverage; therefore, a Kerr comb source could potentially be used to replace a laser transmitter in a wavelength-division multiplexing system. Under different pump conditions, the Kerr comb has several dynamic regimes including different noise properties and different frequency spectra which could affect its application in optical communications. Thus, it would be interesting to study the fundamental physics of Kerr frequency comb generation and further investigate its effects on the communication system performance. ❧ The first part of this dissertation is the study of Kerr frequency comb generation. First, a double-slot waveguide with low and flattened dispersion is designed, which could be potentially beneficial for a broadband comb generation. Second, nonlinear conversion efficiency in Kerr comb generation has been analytically and numerically investigated. Third, the effect of a breather soliton comb on communication system performance has been further numerically studied. Then, we numerically investigate the effect of high-order dispersion on Kerr comb generation in microresonators characterized with anomalous dispersion. Last, we theoretically and experimentally demonstrate that one polarized comb could be used to create an orthogonally polarized comb via cross-phase modulation effect and these two combs interact with each other in one microresonator. ❧ The second part of this dissertation is about the experimental demonstration of Kerr frequency comb in the application of optical communications. First, we demonstrate optical wavelength multicasting using Kerr frequency comb lines. Second, two pumps are used to generate high-coherence primary Kerr combs, which shows that the primary comb state could also be used for multichannel communication. Last, the combination of Kerr and electro-optical combs has been demonstrated in a coherent communication link, which indicates the possibility of obtaining more data channels in the system