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<p class="MsoNormal"><span style="color:#1F497D">Correction: It is of course on Wednesday 25<sup>th</sup> November 2015 (not 24<sup>th</sup> as in the previously sent email).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="mso-fareast-language:EN-GB">From:</span></b><span lang="EN-US" style="mso-fareast-language:EN-GB"> Daniel Oi
<br>
<b>Sent:</b> 20 November 2015 16:28<br>
<b>To:</b> physstaff@phys.strath.ac.uk<br>
<b>Subject:</b> Colloquium: Wed 25/11/2015 "Twisted laser pulses and twisted plasma waves" Jose Mendonca (Lisbon)<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Next week’s John Anderson Physics Colloquium will be given by Jose Mendonca (Lisbon). As usual, there will be tea/coffee afterwards.<o:p></o:p></p>
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<p class="MsoNormal">Title: Twisted laser pulses and twisted plasma waves<o:p></o:p></p>
<p class="MsoNormal">Speaker: Prof Jose T Mendonca (IPFN/IST, Universidade de Lisboa, Portugal)<o:p></o:p></p>
<p class="MsoNormal">Time/Date: 3pm Wednesday 2<span style="color:#1F497D">5</span><sup>th</sup> November 2015<o:p></o:p></p>
<p class="MsoNormal">Venue: John Anderson Building JA3.14<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Abstract:<o:p></o:p></p>
<p class="MsoNormal">We give an overview of our recent work on the physics of intense laser pulses carrying orbital angular momentum (OAM), and on the resulting laser-matter interactions. Twisted laser pulses are electromagnetic vortices, which can be represented
by Laguerre-Gauss modes. They have been explored in optics during the last twenty years, but recently the problem emerged in plasma physics, where different kinds of new processes have been identified. Intense laser-matter interactions lead to the formation
of dense plasmas, therefore plasma effects are naturally linked with intense laser pulses with OAM. First of all, qualitative changes occur in a plasma because, not only electromagnetic waves but also longitudinal oscillations (such as plasmons and phonons)
with OAM can be excited. In particular, these electrostatic waves with OAM display qualitatively new kinetic properties, such as a modified Landau resonance.<o:p></o:p></p>
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<p class="MsoNormal">Other nonlinear effects associated with laser OAM propagation in plasmas were also considered. This includes Raman and Brillouin stimulated scattering, the inverse Faraday effect with linear polarization, radiation pressure effects and
high harmonic generation with OAM. In particular, it has been shown that twisted laser wakefields can be excited by short laser pulses with OAM, leading to the formation of toroidal (or donut shaped) density perturbations behind the pulse.
<o:p></o:p></p>
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<p class="MsoNormal">This could possibly lead to efficient positron acceleration in the nonlinear regime, and to the formation of energetic electron hollow beams. New regimes of intense magnetic field generation have also been identified. Finally, we discuss
perspectives for future theoretical and experimental work related with OAM laser beams and other twisted modes in a plasma.<o:p></o:p></p>
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