Physics Graduate Student Seminar seminar

Title: Exploring nonlinear light-matter interaction processes with orbital angular momentum beams

Supervisors: Prof. Marcelo Ciappina (GTIIT) and Prof. Michael Krueger (Technion)

Speaker: Bikash Kumar Das (PhD Student in Physics)

Zoom link: https://technion.zoom.us/j/97851719100

Abstract

Optical vortices, light beams carrying orbital angular momentum (OAM), have reshaped modern photonics, yet their use in strong-field physics and non-linear optics is only beginning to unfold. Intense laser–matter interactions such as high-order harmonic generation (HHG) and above-threshold ionization with OAM beams have revealed coherent control of HHG in gases, including robust OAM transfer, conserved divergence across harmonic orders, and even the formation of twisted attosecond pulses. However, most studies rely on conventional vortex beams, where increasing OAM reduces peak intensity and limits efficient high-order harmonic generation.

To overcome this limitation, we investigate HHG driven by perfect optical vortex (POV) beams, whose intensity distribution is independent of OAM. Using a multiscale model, we show that POV beams can generate short-wavelength harmonics with very high OAM, maintaining similar divergence and following the linear OAM-scaling law. By superposing linearly polarized OAM beams with different waists or amplitudes, we further demonstrate flexible control of the harmonic OAM and derive a generalized OAM selection rule.

We also extend our analysis to solid-state HHG in ZnO using a dedicated theoretical framework that reproduces experimental observations and enables the synthesis of attosecond vortices. Altogether, these results highlight new opportunities for generating high-OAM vortex beams from the visible to deep-UV, broadening the scope of strong-field, attosecond physics and ultrafast photonics.