title: High Orbital Angular Momentum Harmonic Generation.
abstract: We identify and explore a high orbital angular momentum (OAM) harmonics generation and amplification mechanism that manipulates the OAM independently of any other laser property, by preserving the initial laser wavelength, through stimulated Raman backscattering in a plasma. The high OAM harmonics spectra can extend at least up to the limiting value imposed by the paraxial approximation. We show with theory and particle-in-cell simulations that the orders of the OAM harmonics can be tuned according to a selection rule that depends on the initial OAM of the interacting waves. We illustrate the high OAM harmonics generation in a plasma using several examples including the generation of prime OAM harmonics. The process can also be realized in any nonlinear optical Kerr media supporting three-wave interactions.
authors.affiliation: GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.
authors.forename: J
authors.initials: J
authors.lastname: Vieira
authors.affiliation: Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX, United Kingdom.
authors.forename: R M G M
authors.initials: RM
authors.lastname: Trines
authors.affiliation: GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.
authors.forename: E P
authors.initials: EP
authors.lastname: Alves
authors.affiliation: GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.|DCTI/ISCTE Lisbon University Institute, 1649-026 Lisbon, Portugal.
authors.forename: R A
authors.initials: RA
authors.lastname: Fonseca
authors.affiliation: GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.
authors.forename: J T
authors.initials: JT
authors.lastname: Mendonça
authors.affiliation: Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX, United Kingdom.
authors.forename: R
authors.initials: R
authors.lastname: Bingham
authors.affiliation: Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX, United Kingdom.|Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom.
authors.forename: P
authors.initials: P
authors.lastname: Norreys
authors.affiliation: GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.
authors.forename: L O
authors.initials: LO
authors.lastname: Silva