# Lund University Publications

## LUND UNIVERSITY LIBRARIES

### Sources and Diagnostics for Attosecond Science

(2012) In Lund Reports on Atomic Physics LRAP-466.
Abstract (Swedish)
Popular Abstract in English

What is a photographic camera flash good for? The easy answer is “to illuminate”.

There is more to it though: the duration of a camera flash is usually much shorter than the shutter speed of the camera. This allows us to take sharp pictures of fast objects with an inexpensive camera. Ultrafast science is based on a similar principle: no shutter is capable of opening and closing fast enough to “freeze” the motion of molecules breaking up and forming new ones on a chemical reaction; or, much faster, electrons “spinning” around the nucleus of an atom. The trick is to use very short light pulses (our flashes). Events like the ones described take place in times as short as femtoseconds and... (More)
Popular Abstract in English

What is a photographic camera flash good for? The easy answer is “to illuminate”.

There is more to it though: the duration of a camera flash is usually much shorter than the shutter speed of the camera. This allows us to take sharp pictures of fast objects with an inexpensive camera. Ultrafast science is based on a similar principle: no shutter is capable of opening and closing fast enough to “freeze” the motion of molecules breaking up and forming new ones on a chemical reaction; or, much faster, electrons “spinning” around the nucleus of an atom. The trick is to use very short light pulses (our flashes). Events like the ones described take place in times as short as femtoseconds and attoseconds, respectively. If we want to see what happens, for example, during a chemical reaction, and not only the before and after, we need a flash shorter than the time it takes to occur. But how short is a femtosecond? And an attosecond? A femtosecond is 0.000000000000001 seconds (or 10−15 s), and an attosecond is one thousand times smaller. To put it in perspective, suppose you have a clock and that, at each second, your clock would fall behind one femtosecond. How long would it take for it to be one second off? It would take longer than thirty million years. There is a fundamental limitation to how short a light pulse can be. Light is an oscillation, or vibration, of the electric and the magnetic fields, that propagate as waves. Visible light, that our eyes can perceive, has oscillations periods of about two femtoseconds, and a light pulse cannot be shorter than that. To create even shorter pulses, we have to go higher in the frequency spectrum, towards X-rays. Light pulses with durations of some femtoseconds are nowadays generated directly from lasers. These laser pulses can then be used to interact with matter and generate light at higher frequencies, and even shorter pulses can be created, with durations of around one hundred attoseconds.

This thesis describes the work undertaken on creating, taming, measuring and using such short light pulses, both in the femtosecond and attosecond regime. Creating such short light pulses poses a considerable technical challenge. Interestingly, it is as difficult to keep them short as it is to create them, and the same goes for characterizing them: since these are the shortest events artificially created, we don’t have an even shorter light pulse to measure them, so we have to use these pulses to measure themselves. (Less)
Abstract
Ultrafast science refers to physical events that happen on the femtosecond (1 fs=10^-15 s) and attosecond (1 as=10^-18 s) timescales. Generation of attosecond pulses is usually achieved by interacting high-intensity femtosecond pulses with matter (typically gases), in a process called high-order harmonic generation (HHG). Under the correct conditions, this process leads to the creation of sub-fs pulses in the extreme ultraviolet (XUV) region.

The work presented in this thesis focuses around generating, characterizing, and applying ultrashort light pulses, both in the femtosecond and attosecond domain.

The first part describes the effort on the femtosecond laser sources, with emphasis on carrier-envelope phase (CEP)... (More)
Ultrafast science refers to physical events that happen on the femtosecond (1 fs=10^-15 s) and attosecond (1 as=10^-18 s) timescales. Generation of attosecond pulses is usually achieved by interacting high-intensity femtosecond pulses with matter (typically gases), in a process called high-order harmonic generation (HHG). Under the correct conditions, this process leads to the creation of sub-fs pulses in the extreme ultraviolet (XUV) region.

The work presented in this thesis focuses around generating, characterizing, and applying ultrashort light pulses, both in the femtosecond and attosecond domain.

The first part describes the effort on the femtosecond laser sources, with emphasis on carrier-envelope phase (CEP) stability and control, and temporal and spatial characterization. An existing high-power (30 fs, 6 mJ) laser system was successfully CEP-stabilized, using an acousto-optic programmable dispersive filter (AOPDF) for CEP control. CEP detection at kilohertz rates is also demonstrated.

A method for the characterization of ultrashort laser pulses, based on a glass wedges and chirped mirror compressor, has been developed and demonstrated on pulses in the few-cycle regime. This technique, together with spectral interferometry, has been used to characterize in space and time femtosecond laser pulses, in the optical / near-infrared domain.

The second part deals with the HHG sources and applications. The spatial coherence of one of the HHG sources, together with its high photon flux, has allowed us to perform single-shot holography in the extreme ultraviolet (XUV) domain. Another HHG source, with lower power but higher repetition rate, was used for the characterization of properties of argon and helium atoms. For this, a technique typically used for the temporal characterization of attosecond pulse trains, RABBITT (reconstruction of attosecond beating by interfering two-photon transitions) was used, allowing us to study the phase of a resonant two-photon ionization in helium, and to measure photoemission delays in argon. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
• Prof. Morgner, Uwe, Institute for Quantum Optics, Hannover University, Hannover, Germany
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Pulse Compression, High-order Harmonic Generation, Ultrafast, Ultrashort, Attosecond, Femtosecond, Pulse Characterization, Fysicumarkivet A:2012:Miranda
in
Lund Reports on Atomic Physics
volume
LRAP-466
pages
218 pages
defense location
Rydberg Hall, Department of Physics, Professorsgatan 1, Lund University Faculty of Engineering
defense date
2012-11-16 10:15
external identifiers
• other:Lund Reports on Atomic Physics, LRAP-466
ISSN
0281-2762
ISBN
978-91-7473-392-1
language
English
LU publication?
yes
id
5f50d945-3e3e-44d7-a8ba-bf78acebbf39 (old id 3131649)
date added to LUP
2012-10-23 14:39:42
date last changed
2016-09-19 08:45:00
```@phdthesis{5f50d945-3e3e-44d7-a8ba-bf78acebbf39,
abstract     = {Ultrafast science refers to physical events that happen on the femtosecond (1 fs=10^-15 s) and attosecond (1 as=10^-18 s) timescales. Generation of attosecond pulses is usually achieved by interacting high-intensity femtosecond pulses with matter (typically gases), in a process called high-order harmonic generation (HHG). Under the correct conditions, this process leads to the creation of sub-fs pulses in the extreme ultraviolet (XUV) region.<br/><br>
The work presented in this thesis focuses around generating, characterizing, and applying ultrashort light pulses, both in the femtosecond and attosecond domain.<br/><br>
The first part describes the effort on the femtosecond laser sources, with emphasis on carrier-envelope phase (CEP) stability and control, and temporal and spatial characterization. An existing high-power (30 fs, 6 mJ) laser system was successfully CEP-stabilized, using an acousto-optic programmable dispersive filter (AOPDF) for CEP control. CEP detection at kilohertz rates is also demonstrated.<br/><br>
A method for the characterization of ultrashort laser pulses, based on a glass wedges and chirped mirror compressor, has been developed and demonstrated on pulses in the few-cycle regime. This technique, together with spectral interferometry, has been used to characterize in space and time femtosecond laser pulses, in the optical / near-infrared domain.<br/><br>
<br/><br>
The second part deals with the HHG sources and applications. The spatial coherence of one of the HHG sources, together with its high photon flux, has allowed us to perform single-shot holography in the extreme ultraviolet (XUV) domain. Another HHG source, with lower power but higher repetition rate, was used for the characterization of properties of argon and helium atoms. For this, a technique typically used for the temporal characterization of attosecond pulse trains, RABBITT (reconstruction of attosecond beating by interfering two-photon transitions) was used, allowing us to study the phase of a resonant two-photon ionization in helium, and to measure photoemission delays in argon.},
author       = {Miranda, Miguel},
isbn         = {978-91-7473-392-1},
issn         = {0281-2762},
keyword      = {Pulse Compression,High-order Harmonic Generation,Ultrafast,Ultrashort,Attosecond,Femtosecond,Pulse Characterization,Fysicumarkivet A:2012:Miranda},
language     = {eng},
pages        = {218},
school       = {Lund University},
series       = {Lund Reports on Atomic Physics},
title        = {Sources and Diagnostics for Attosecond Science},
volume       = {LRAP-466},
year         = {2012},
}

```