Characterisation of ultrashort pulses

Thesis

The main topic of this thesis is the development of new characterization techniques for Ultrashort pulses with particular focus on pulses with complex spectra, often obtained with light pulse synthesisers. More in detail, I have addressed the longstanding problem of retrieving the spectral phase of a pulse which exhibits a spectral gap, i.e. a spectral null larger than any of the spectral features of the pulse. The major challenge in this scenario is attaining a reliable reconstruction of the relative spectral phase between the spectral components. I discuss the different approaches that I have employed in order to achieve this objective.

The first result has been the realisation of a low-power XFROG for the charac- terisation of a coherent pulse synthesis source developed by Prof. D. Reid’s group at Heriot-Watt University. We used it to characterise, compress, and synchronise the individual components of the source, however the relative phase remained elusive. In order to solve this problem, a radically new characterisation technique needed to be implemented. This consisted in the development of a new algorithm (MICE), which enabled the mutual characterisation of multiple fields, and in a new experimental implementation of the well-known SPIDER technique (SPICE). Both the algorithm and the new technique have been tested experimentally in a proof-of-principle experiment which constitutes the main result of this work. The appeal of these solutions for mastering light synthesisers will likely stimulate further refinements towards making it the standard technique for complex spectra.

Authors: Gianani, I

• DOI: 10.5287/ora-mqg7rnmjr
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Metrology; Ultrafast; Optics
• Subjects: Physics