Conservation of Torus-knot Angular Momentum in High-order Harmonic Generation

• Published in: Physical review letters 2019-05, Vol.122 (20)
• Main Authors: Pisanty, Emilio, Rego, Laura, San Román, Julio, Picón, Antonio, Dorney, Kevin M., Kapteyn, Henry C., Murnane, Margaret M., Plaja, Luis, Lewenstein, Maciej, Hernández-García, Carlos
• Format: Article
• Language: English
• Subjects: angular momentum of light; high-harmonic generation; nonlinear optics; nonperturbative methods; optical vortices; physics; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; polarization of light; quantum description of light-matter interaction; spin-orbit coupling; strong-field approximation; strong-field-induced spectra; topology; ultrafast optics; ultrafast phenomena; ultrafast pulses
• ISSN: 0031-9007; 1079-7114

High-order harmonic generation stands as a unique nonlinear optical up-conversion process, mediated by a laser-driven electron recollision mechanism, which has been shown to conserve energy, linear momentum, and spin and orbital angular momentum. Here, we present theoretical simulations that demonstrate that this process also conserves a mixture of the latter, the torus-knot angular momentum Jγ, by producing high-order harmonics with driving pulses that are invariant under coordinated rotations. Here, we demonstrate that the charge Jγ of the emitted harmonics scales linearly with the harmonic order, and that this conservation law is imprinted onto the polarization distribution of the emitted spiral of attosecond pulses. We also demonstrate how the nonperturbative physics of high-order harmonic generation affect the torus-knot angular momentum of the harmonics, and we show that this configuration harnesses the spin selection rules to channel the full yield of each harmonic into a single mode of controllable orbital angular momentum.