Conservation of orbital angular momentum for high harmonic generation of fractional vortex beams

Abstract

This work demonstrates conservation of average orbital angular momentum for high harmonic generation of fractional vortex beams. High harmonics are generated in reflected light beams in a three-dimensional particle-in-cell simulation. The average orbital angular momentum of the beam is calculated when a relativistic linearly polarized fractional vortex beam impinges on a solid foil. The harmonic generation progress can be well explained by using the vortex oscillating mirror model. Both simulation and theoretical analysis show that the average orbital momentum of the nth harmonic is n times that of the fundamental frequency beam. This provides evidence that the average orbital angular momentum obeys momentum conservation during the harmonic generation of fractional vortex beams.

Generation of terahertz radiation with fractional or integer OAMs from a fractional-order vortex two-color field

“…The development of ultrafast vortex beams has opened new possibilities for the generation of filamentation [22,23], supercontinuum [24], high-order harmonics [25][26][27][28][29][30][31], and even terahertz (THz) pulses [32][33][34][35][36] with complex structures. It has been demonstrated that the nonlinear phenomena are crucial during the interaction of laser with bulk media and atmospheric air [23,[25][26][27][28][29][30][31]. As for frequency up-conversion process of high-order harmonic generation via vortex laser-gas interaction, the OAMs of the high-order harmonics for both integer and fractional schemes, always scales with the harmonic orders due to OAM conservation [25][26][27][28][29][30][31].…”

Generation of isolated intense vortex laser with transverse angular momentum

“…For a general vortex beam, OAM of each photon it carries is lℏ in the propagation direction. While the application of the vortex beam with an intensity <10 17 W cm −2 has been realized in various fields [3][4][5][6][7][8][9], the generation and application of relativistic vortex beam applying plasma as the nonlinear medium has been a subject of interest in recent years [10][11][12][13][14][15][16], such as the positive particle acceleration [17,18], high mode vortex beam generation [19][20][21], and specific scientific law correction [22], etc.…”

“…HHG is one of the most applied methods of getting vortex beams with a high topological charge for various applications. Regarding the present laser level, using a gas exposed to light (∼10 [14][15][16] W cm −2 ) [37][38][39][40][41][42] or plasma target exposed to intense light (>10 18 W cm −2 ) [19][20][21][43][44][45][46][47] is the most promising approaches toward HHG. It has been confirmed that the topological charge of the harmonics is proportional to its order [19,38,39,47] when only one driving pulse is used.…”

Direct Acceleration of an Annular Attosecond Electron Slice Driven by Near-Infrared Laguerre–Gaussian Laser

“…The relativistic LG laser is expected to open new doors for particle manipulation in the DLA regime, because the hollow intensity distribution of the LG laser may result in the formation of a transverse potential well about the beam axis, similar to the charge-separated field structure in the bubble regime of LWFA [42][43][44][45]. It is believed that electrons can be accelerated in a concentrated manner in a new type of "bubble" regime, to overcome some of the drawbacks of Gaussian-laser driven DLA to a certain extent [46][47][48][49][50].…”