High Harmonic Generation Polarization States: Circular Linear and Foucault Fan

by Avner Fleischer

at Quantum optics seminar

Thu, 26 Jan 2017, 15:30
Physics building (#54) room 207

Abstract

High harmonic generation HHG has been providing unique experimental access to ultrafast processes The polarization state of high order harmonics HHs is generally linear in the vast majority of HHG studies and applications The recent demonstration of efficient high harmonics with fully controlled polarization state ranging from circular with right helicity through linear to circular with left helicity pumped by a counter rotating bi chromatic laser field using either a Mach Zehnder configuration 1 2 or an inline setup 3 opened a route for new opportunities e g investigating ultrafast chiral dynamics with unprecedented temporal and spatial resolution using table top sources 4 In the talk I will describe the schemes we developed in order to gain HHG polarization control I will show how we used our source to explore the role of spin mixing in HHG 1 5 Finally I will demonstrate how we advanced high harmonic polarization control even further by suggesting a completely new concept in HHG: Foucault fan polarization fan HHG 6 which yield spectrum of harmonics where the polarization within the spectral bandwidth of each harmonic peak is not fixed but rather significantly frequency dependent For example the interaction of counter rotating circularly polarized bichromatic drivers having close central frequencies with isotropic gas leads to the emission of Foucault fan harmonics where each harmonic in the spectrum has the following property: it is nearly circularly polarized in one tail of the harmonic peak linear in the center of the peak and nearly circular with the opposite helicity in the opposite tail Foucault fan harmonics are obtained as a result of multiple at least two head on recollisions of electrons with their parent ions occurring from different angles in a two dimensional plane The use of bichromatic drivers with close central frequencies largely preserves the single cycle single atom and macroscopic physics of ordinary high harmonic generation where both the driver and high harmonics are linearly polarized Thus it should offer several attracting features including i a direct route for extending the maximal photon energy of observed helical high harmonics to keV by using bichromatic drivers only in the mid IR region and ii utilizing phase matching methods that were developed for high harmonic generation driven by quasi monochromatic pulses e g pressure tuning phase matching These Foucault fan harmonics may be utilized for exploring non repetitive ultrafast chiral phenomena e g dynamics of magnetic domains in a single shot References 1 A Fleischer et al Spin angular momentum and tunable polarization in high harmonic generation Nat Photon 8 543 549 2014 2 O Kfir et al Generation of bright phase matched circularly polarized extreme ultraviolet high harmonics Nat Photon 9 99 105 2015 3 O Kfir et al In line production of a bi circular field for generation of helically polarized high order harmonics Appl Phys Lett 108 211106 2016 4 O Smirnova et al Opportunities for chiral discrimination using high harmonic generation in tailored laser fields J Phys B 48 234005 2015 5 E Pisanty et al Spin conservation in high order harmonic generation using bicircular fields Phys Rev A 90 043829 2014 6 A Fleischer et al High order harmonics with frequency varying polarization within each harmonic accepted to J Phys B 2017

Created on 19-01-2017 by Bar Lev, Yevgeny (ybarlev)
Updaded on 19-01-2017 by Bar Lev, Yevgeny (ybarlev)