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The Physics of Ultrabroadband Frequency Comb Generation and Optimized Combs for Measurements in Fundamental Physics

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[Technical Report, Final Report]

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This project had as its aim to carry out targeted numerical and experimental studies into the properties of optical frequency comb sources. The generation of frequency combs is intimately connected with the nonlinear spectral broadening that occurs in optical fibers due to the Kerr effect, and our initial work focused on fundamental studies examining the sensitivity of such nonlinear spectral broadening to input noise, and the development of techniques to reduce such noise with the presence of an external seed source. To perform fundamental studies of this process, we considered the case of spontaneous four wave mixing or modulation instability, which is the noise-driven analogue of the process generating frequency combs. Our experiments showed control of both the spectral and noise properties of optical fibre spectral broadening using an incoherent seed with power at the 106 level relative to the pump, and varying the seed wavelength revealed enhancement of the spectrally-broadened bandwidth and improvement in signal-to-noise ratio as the seed coincides with the peak of the calculated four wave mixing modulation instability gain. Stochastic nonlinear Schrodinger equation simulations were shown to be in very good agreement with experiment. An important feature of our work was the development of a real time technique suitable for the measurement of spectral fluctuations, and the grant was indispensable in allowing us to purchase and optimise the necessary equipment. This real-time technique has become a standard technique allowing the study of nonlinear spectral broadening under a wide range of conditions. The results of this project have direct impact on the understanding of the nonlinear wave mixing interactions in frequency combs, and will feed into future studies of comb dynamics and dissipative soliton characterisation using real-time measurement techniques.

Subject Categories:

  • Optics
  • Test Facilities, Equipment and Methods
  • Operations Research

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[A, Approved For Public Release]