Spatio-temporal characterization of high harmonic generation for plasma diagnostics

Jayanath Chalappurath Payyan Koliyadu

Key information

Authors:

Jayanath Chalappurath Payyan Koliyadu (Jayanath Chalappurath Payyan Koliyadu)

Supervisors:

Marta Leitão Mota Fajardo (Marta Leitão Mota Fajardo); Philippe Zeitoun; Gonçalo Nuno Marmelo Foito Figueira (Gonçalo Nuno Marmelo Foito Figueira)

Published in

07/02/2018

Abstract

The extreme ultra-violet (XUV) spectral region of the electromagnetic spectrum is characterized by shorter wavelengths, higher photon energies and a possibility to support lower pulse duration compared to visible or infrared radiation. These properties make XUV pulses an apt tool for applications like imaging, probing and lithography with a spatial resolution reaching up to tens of nanometers and temporal resolution on the order of femtoseconds to attoseconds. The available sources of coherent XUV radiation are high harmonic generation (HHG), X-ray lasers (XRL) and free electron lasers (FEL). Work done in this thesis is focused on XUV pulses from HHG. In order to use XUV pulses from HHG for different applications, it is important to optimize its photon number and to characterize the stability in terms of energy, pointing, spatial as well as temporal properties. For experiments like plasma probing, holography, coherent diffraction imaging and XRL seeding it is necessary to have spatially characterized, and energy optimized XUV pulses with stability in pointing and energy. For spatial characterization of XUV pulses and XUV optics, mainly the spatial phase characterization is considered. Knowing the spatial phase of the XUV pulse helps to optimize the wavefront of the pulses and thereby improving the focusing of XUV pulses. The XUV wavefront is characterized mostly using Hartmann wavefront sensors (WFS) for XUV radiation. For temporal characterization of XUV pulses from HHG, different ex-situ and in-situ methods have been proposed and used. An in-situ method called spatially encoded arrangement - spectral phase interferometry for direct electric field reconstruction (SEA-SPIDER) can be used to efficiently characterize pulse duration of XUV pulses from HHG.