Advanced Shaping of Quasi-Bessel Beams for High-Intensity Applications

TL;DR

The paper identifies boundary-term interference from sharp truncation as the origin of longitudinal oscillations in quasi-Bessel beams produced by axiparabolas. It introduces two robust control strategies—amplitude shaping and phase-only optics—to suppress these oscillations and validates them with both simulations and experiments, including a trefoil aberration observation. Beyond suppression, it demonstrates programmable complex longitudinal profiles, establishes a fundamental longitudinal-resolution limit, and shows that segmented optics with temporal delays can bypass this limit to realize high-contrast, fine-structured focal lines. The findings enable precise tailoring of extended focal lines for high-intensity laser-plasma interactions, advanced photon sources, and other ultrafast, high-field applications, with broad relevance to non-diffractive beam geometries.

Abstract

Quasi-Bessel beams produced by axiparabolas are increasingly used in high-intensity laser applications, yet their longitudinal profiles exhibit unwanted oscillations that limit their effectiveness. Here we identify the physical origin of these distortions and develop a general strategy to control the on-axis intensity of extended focal lines. By combining analytical insight with numerical and experimental validation, we show how both smooth and sharply structured longitudinal profiles can be reliably produced. This establishes a robust framework for tailoring quasi-Bessel beams in regimes relevant to laser-plasma acceleration, advanced photon sources, and other high-field applications.

Figures (9)

• Figure 1: Intensity along the optical axis at the end (a) and at the beginning (b, c, d) of the focal line for a hole radius of $r_h = 20$ mm (b), $r_h = 10$ mm (c), and $r_h = 0$ mm (d). The blue curves were computed with Axiprop, while the orange curves were obtained using Eq. (\ref{['eq:field_model']}).
• Figure 2: Intensity along the optical axis at the beginning (a) and at the end (b) of the focal line for a super-Gaussian laser pulse with a Gaussian central hole, as defined by Eq. (\ref{['eq:def_las']}).
• Figure 3: Experimental on-axis intensity profiles obtained with a sharp hole (orange) and a Gaussian hole (blue) with $r_h = 11.6$ mm and $r_h = 16.75$ mm respectively. Theoretical prediction from simulation is shown as dashed lines.
• Figure 4: On-axis intensity profiles obtained from Axiprop simulations using the modified phase approach. Profiles are shown for $r_0 = 10$ mm (blue line) and $r_0 = 15$ mm (orange line). the dotted lines correspond to the profiles obtained from Eq. \ref{['eq:field_stat']}.
• Figure 5: Experimental on-axis intensity profiles obtained without modulation (blue) and a phase modulation (orange) with $r_h = 10$ mm.