Development of Nonlinear and Ultra-low Noise Fiber Technologies
Creators: name: Edelmann, Marvin
Publisher: name: Deutsches Elektronen-Synchrotron, DESY, Hamburg
Year: 2022

description: Masterarbeit, University of Oldenburg/HS Emden Leer, 2021; 67 pp. (2022). = Masterarbeit, University of Oldenburg/HS Emden Leer, 2021
description: Fiber-optic technologies for the generation of ultra-low noise optical pulse trains have asevere impact on a great variety of scientific fields and industrial applications such asfrequency metrology, synchronization and timing in free-electron laser facilities and particle accelerators, photonic microwave generation and quantum technologies. The fasttechnological progression of these applications necessitates a constant improvement ofthe underlaying fiber-optic laser systems in every aspect. The scope of this thesis is thedevelopment of novel fiber-optic devices and the discovery of new physical possibilitiesto overcome the currently existing boundaries of ultrafast fiber lasers and their ultra-lownoise applications.To this end, an experimental and theoretical study of state-of-the-art fiber oscillator modelocked with nonlinear amplifying loop mirrors is conducted, a cavity structure thatdemonstrated record ultra-low noise characteristics in conjunction with superior environmental stability. A theoretical model is derived that describes the interaction of the steadystate fluctuating intracavity amplitude with the nonlinear dynamics of the saturable absorber based on amplitude-noise transfer coefficients. To experimentally investigate theinfluence of this interaction decoupled from the optical feedback of the cavity, a novelnonlinear fiber amplifier is constructed which precisely replicates the physical mechanisms of an isolated roundtrip in the oscillator for an auxiliary input generated pulse train.The combined results of the theoretical investigation and the systematic measurementsreveal the existence of an intrinsic amplitude-noise suppressing mechanism that acts onthe circulating intracavity field once per roundtrip. The discovery of this mechanism givesan explanation for the superior noise performance of NALM mode-locked lasers for thefirst time.The second part of this thesis is aimed at the construction and optimization of a devicethat utilizes the discovered nonlinear mechanism for quantum-limited noise suppression.The implementation of an artificial sinusoidal transmission-function in a phase-biased,self-stabilized Sagnac interferometer with all-fiber integrated amplifier enables highlyefficient and broadband suppression of the input amplitude-fluctuations. In the experiment, quantum-limited amplitude-noise suppression by up to 20 dB down to the shotnoise limit at -151.1 dBc/Hz is demonstrated for the frequency range &gt;100 kHz with asimultaneous signal amplification of 13.5 dB. The system shows an extraordinary efficiency in conjunction with a high degree of tunability based on the phase-bias settings.VHence, a great potential for a variety of high-end applications is revealed such as lownoise microwave generation and frequency metrology together with the possibility for thegeneration of squeezed quantum states of light under the right conditions.The third part of this thesis is aimed at the development of a novel I-shaped fiber oscillatormode-locked with the optical Kerr-effect that uses coherent pulse division and recombination to reduce the roundtrip nonlinear phase shift and dramatically increase the achievable intracavity pulse energy by 6.5 dB. In addition, a substantial improvement of thenoise performance is verified for increasing pulse divisions with a suppression of the output amplitude-fluctuations by up to 9 dB for three divisions in the frequency range from10 kHz to 2 MHz. In combination with other established mechanisms to reduce the roundtrip nonlinear phase shift based on dispersion-management or scaling of the fiber coresize, the here developed divided pulse oscillator enables a promising approach for nextgen ultra-low noise and environmentally stable fiber oscillators with high intracavitypower.