Low noise frequency combs and injection locking for broadly tunable laser sources and tomography

Doktorsavhandling, 2023

Lasers have revolutionized the world of physics by providing a highly coherent source of photons which may be used for a large variety of purposes. Here, we study the noise properties of frequency combs - a special class of frequency stabilized and mutually coherent multi-mode lasers, as well as the optical injection locking of comb tones as a means for low noise amplification and tone selection. A variety of applications are discussed, along with more fundamental properties of the systems in question. Particular focus is placed on the exceptionally low phase noise of these sources.

Several comb sources are investigated, including bulk electo-optic combs, on-chip anomalous dispersion micro-combs, and on-chip normal dispersion photonic molecules. Similarly, several sources are investigated for their use in optical injection locking, including DFB slave laser arrays, and multi-mode FP lasers. Noise mitigation is also investigated at length, with a focus on PID control loops and thermorefractive noise reduction at high temperature. Furthermore, significant attention is given to the noise analysis of frequency combs and optical injection locking. The mutual coherence of comb tones is investigated, along with the growth of noise as a function of comb mode index. Finally the role of injected noise is studied in the case of optical injection locking near the limit of stability for locking.