| Author: | Shi, Zhaolong |
| Title: | Dispersion designed optical frequency combs generation in nonlinear microcavities |
| Advisors: | Huang, Dongmei (EEE) |
| Degree: | M.Sc. |
| Year: | 2023 |
| Department: | Department of Electrical and Electronic Engineering |
| Pages: | xi, 67 pages : color illustrations |
| Language: | English |
| Abstract: | Kerr optical frequency combs (OFCs) generated in microcavity have the advantages of compact structure and high repetition frequency, which have been widely applied in the fields of astronomical spectral analysis, arbitrary waveform generation, terabit-scale coherent optical communication, etc. Recently, with the development of the nanofabrication of lithium niobate (LN) photonic devices, high Q factor LN microcavity is possible on a chip-scale platform for the exploration of nonlinear optical effects such as second harmonic generation, Kerr comb generation et al. For the Kerr comb generation in LN microcavity, there are still several challenges including how to easily generate Kerr frequency combs, how to optimize the dispersion to realize broadband spectrum, and how to combine χ2 and χ3 to generate Kerr comb. In this thesis, we will overcome the proposed challenges and theoretically investigate the Kerr comb generation in LN microcavity. Deterministic generation of single soliton Kerr frequency comb in micro-cavity by a single shot pulse-trigger is proposed and demonstrated. We also study the secondary nonlinear OFCs generation and spectral broadening of OFCs via dispersion engineering. The specific research contents and conclusions are as follows: I. The deterministic generation of Kerr OFCs in a LiNbO₃ micro-cavity assisted by a trigger is investigated through modeling and numerical simulations. The results show that the Kerr OFCs can be deterministically excited through the use of continuous wave (CW) and pulse trigger. Soliton crystals can be controlled by varying the CW detuning and the offset frequency of the pulse trigger. II. Numerical simulations of the process of generating an optical frequency comb in a microcavity with anomalous dispersion, assisted by the second harmonic, have been carried out to obtain a single-soliton second-harmonic optical frequency comb and analyzed. III. We propose a simple method for dispersion engineering in LiNbO₃ slab waveguide for broadband frequency comb generation. We analyze how the geometrical parameters affect the dispersion. Based on our results, we propose a LiNbO₃ micro-cavity design for broadband OFCs generation. Through dispersion engineering, two dispersive waves (DW) can be used to broaden the OFCs. Simulation results show that by adjusting structural parameters, such as waveguide thickness and width, the dispersive wave emission can be controlled, and the bandwidth can be broadened to 4/5 octaves. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| 8597.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 5.49 MB | Adobe PDF | View/Open |
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