Application of multi-colour femtosecond pulses towards light-matter interactions
File(s)
Author(s)
Pettipher, Allan
Type
Thesis
Abstract
Multi-colour femtosecond laser fields provide significant benefits when probing states of
matter, through either increasing the resolution of transient spectroscopy or via optimisation
of highly nonlinear processes. In this thesis, I present several experimental advancements
in the development and application of such laser fields towards novel organic
photovoltaic devices and optimisation of high-harmonic generation (HHG).
In the first case, using sub-10 fs two-coloured fields in a comparative study between
traditional pump-probe techniques and pump-push photocurrent (PPPC), we showed that
PPPC was able to more readily distinguish the bound states of an optically-excited system,
paving the way for new devices to be studied and understood. The experimental system
is poised to explore other less-understood molecular processes in the near future, such as
quantum beating.
For the second, we developed and characterised a three-colour femtosecond field synthesizer
with the goal of generating an approximated ‘perfect waveform’ for HHG. We
combined a 350 μJ, 6.3 fs near infrared pulse with its second harmonic (40 μJ, 46 fs) and
a third, 50 μJ, 41 fs, short-wave infrared field, at 1300 nm. Some technical challenges
remain, such as the phase instabilities of the longer-wavelength field. However, we have
demonstrated that, by using two of the three channels, a significant enhancement to the
flux of isolated attosecond pulses generated by HHG can be achieved without sacrificing
the duration of the attosecond pulse.
matter, through either increasing the resolution of transient spectroscopy or via optimisation
of highly nonlinear processes. In this thesis, I present several experimental advancements
in the development and application of such laser fields towards novel organic
photovoltaic devices and optimisation of high-harmonic generation (HHG).
In the first case, using sub-10 fs two-coloured fields in a comparative study between
traditional pump-probe techniques and pump-push photocurrent (PPPC), we showed that
PPPC was able to more readily distinguish the bound states of an optically-excited system,
paving the way for new devices to be studied and understood. The experimental system
is poised to explore other less-understood molecular processes in the near future, such as
quantum beating.
For the second, we developed and characterised a three-colour femtosecond field synthesizer
with the goal of generating an approximated ‘perfect waveform’ for HHG. We
combined a 350 μJ, 6.3 fs near infrared pulse with its second harmonic (40 μJ, 46 fs) and
a third, 50 μJ, 41 fs, short-wave infrared field, at 1300 nm. Some technical challenges
remain, such as the phase instabilities of the longer-wavelength field. However, we have
demonstrated that, by using two of the three channels, a significant enhancement to the
flux of isolated attosecond pulses generated by HHG can be achieved without sacrificing
the duration of the attosecond pulse.
Version
Open Access
Date Issued
2022-02
Date Awarded
2022-05
Copyright Statement
Creative Commons Attribution Non-Commercial 4.0 International Licence
License URL
Advisor
Tisch, John
Sponsor
Engineering and Physical Sciences Research Council
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)