Doctoral defence Morten Bache

Cascaded Nonlinearities for Ultrafast Nonlinear Optical Science and Applications

Ass. Professor Morten Bache
Technical University of Denmark

Professor Katia Gallo, KTH, Stockholm, Sverige
Professor Dmitry Skryabin, University of Bath, Bath, England

Both opponents are appointed by DTU and have been part of the assessment committee with the chairman also appointed by DTU, Professor Mads Peter Sørensen, DTU Compute.

Unofficial opponents are to address the moderator:

Provost Rasmus Larsen
Building 101A
Technical University of Denmark
Tel.: 45 25 71 42

A copy of the dissertation can be obtained by contacting:
Anna-Maria Lund
Office of Research and Relations
Building 101A
Technical University of Denmark
Tel.: 45 25 71 42

The dissertation:

"Cascaded Nonlinearities for Ultrafast Nonlinear Optical Science and Applications"

English summary

Cascaded nonlinearities in quadratic nonlinear crystals underlie an immensely powerful control over the ultrafast nonlinear response, where it is possible at will to change the sign of the nonlinearity and tune its strength seamlessly from weak to extremely strong. Here the physics behind the cascading nonlinearity is investigated in detail, especially with focus on femtosecond energetic laser pulses being subjected to this nonlinear response. Analytical, numerical and experimental results are used to understand the cascading interaction and applications are demonstrated. The defocusing soliton is of particular interest here, since it is quite unique and provides the solution to a number of standing challenges in the ultrafast nonlinear optics community. It solves the problem of catastrophic focusing and formation of filaments in bulk glasses, which even under controlled circumstances is limited to a few μJ. In contrast, the defocusing soliton can sustain orders of magnitude larger energies. It also solves the challenge of using mature near-IR laser technology to generate ultrashort, coherent and bright mid-IR radiation. The defocusing nonlinear effect that leads to intriguing observations similar to fiber optics are observed numerically and experimentally, including soliton self-compression, soliton-induced resonant radiation, supercontinuum generation, optical wavebreaking and shock-front formation. All this happens despite no waveguide being present, thanks to the defocusing nonlinearity. Finally, the richness of the complex nonlinear system is immense, and as an example the first observation of parametrically tunable resonant radiation is shown, phase-matched to the defocusing soliton in the mid-IR and the visible/near-IR.


Fri 23 Mar 18
14:00 - 18:30




DTU, Lyngby Campus

Anker Engelunds Vej 1

Building 101 A, meeting room 1, (1st floor)