[Physstaff] Colloquium: Wed 25/11/2015 "Twisted laser pulses and twisted plasma waves" Jose Mendonca (Lisbon)

[Daniel Oi]

Correction: It is of course on Wednesday 25th November 2015 (not 24th as in the previously sent email).

From: Daniel Oi
Sent: 20 November 2015 16:28
To: physstaff at phys.strath.ac.uk
Subject: Colloquium: Wed 25/11/2015 "Twisted laser pulses and twisted plasma waves" Jose Mendonca (Lisbon)

Next week's John Anderson Physics Colloquium will be given by Jose Mendonca (Lisbon). As usual, there will be tea/coffee afterwards.

Title: Twisted laser pulses and twisted plasma waves
Speaker: Prof Jose T Mendonca (IPFN/IST, Universidade de Lisboa, Portugal)
Time/Date: 3pm Wednesday 25th November 2015
Venue: John Anderson Building JA3.14

Abstract:
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.

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.

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.
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