PhD defence by Ivan Bravo Gonzalo

Title: Low noise supercontinuum sources for optical coherence tomography


Main supervisor: Prof. Ole Bang, DTU Fotonik
Co-supervisor: Prof. Mads Peter Sørensen, DTU Compute

Evaluation Board

Assoc. Prof. Jesper Lægsgaard, DTU Fotonik
Prof. Goery Genty, Tampere University of Technology, Finland
Prof. John Dudley, University of Besancon, France

Master of the Ceremony

Assoc. Prof. Christos Markos


Supercontinuum fiber laser sources are becoming widely used not only for scientific activities but also for industrial purposes. This is due to their unique properties, which include ultra-broadband spectral coverage, high-power and spatial coherence. Within the applications that can benefit from these exceptional characteristics, here we focused on a powerful biomedical imaging technique called optical coherence tomography. Optical coherence tomography is an optical interferometric technique that provides structural information of the sample with micrometer resolution. Owing to the broadband spectrum of the supercontinuum laser source, the resolution in optical coherence tomography is significantly improved. However, the intrinsic intensity noise of supercontinuum sources can reduce the performance of the system by directly deteriorating the contrast of the images and indirectly limiting the acquisition speed. 

The research presented in this thesis focuses on investigating and optimizing the noise properties of supercontinuum laser sources based on all-normal dispersion silica fibers. This approach for supercontinuum generation has attracted much attention in the recent years due to its potential for producing low noise supercontinuum. We explore here the conditions for low noise operation and limitations of this promising approach. For that, we numerically and experimentally investigate the underlying physics behind the nonlinear phenomena involved in the extreme spectral broadening. As part of the Ph.D. project, a femtosecond fiber laser based on hollow-core fiber compression was also developed. Finally, we compare the noise performance of a femtosecond-pumped all-normal dispersion supercontinuum to that of commercial supercontinuum sources in an optical coherence tomography system for skin imaging.


Fri 12 Oct 18
13:30 - 16:30


Lyngby Campus

Bld. 341, aud. 23