Noise in nonlinear fiber-optic systems

The optical frequency comb (OFC) is a laser-based technology that has revolutionized metrology, enabling timing and frequency measurements with unprecedented precision. Beyond their original purpose, OFCs have been adopted in various fields of fundamental science and emerging technologies such as autonomous driving and wireless communications. However, current challenges in generating low-noise OFC sources at high repetition rates with sufficient optical bandwidth hinder their full potential. To address these challenges, supercontinuum (SC) generation in nonlinear fiber optics is an attractive approach because it can provide a large bandwidth at relatively low pump power, but at the cost of noise amplification. This thesis explores new ways to generate low-noise SC-based OFC sources to meet the ever-increasing demands of these novel applications. The first proposed solution is a hybrid fiber that combines the best qualities of both SC generation regimes. With this fiber, it is possible to generate an ultra-low noise fiber SC covering the 930–2130 nm range with phase coherence close to unity, spectrally resolved relative intensity noise (RIN) as low as 0.05%, and averaging 0.01% over a bandwidth of 750nm, approaching the theoretical limits close to the pump laser noise. The second important result of this work is the development of a new numerical method, capable of simulating entire trains of ultrafast pulses propagating in nonlinear fibers and studying the evolution of their noise properties. We use this model to corroborate and explain measurements of unprecedented low noise observed on a dual-comb SC source, including shot-noise-limited SC generation and up to 20 dB of RIN suppression. Finally, hollow-core fibers are introduced as a promising way to reach new SC regimes, including deep UV pulses and TW peak power.

2024

dissertation

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