A collaborative research team from the Key Laboratory of High-Field Laer Physics, Shanghai Institute of Optics and Fine Mechanics (SIOM) of the Chinese Academy of Sciences (CAS), Zhangjiang Laboratory, and Shanghai Tech University explained the mechanism of the tunable group-velocity of a propagation-invariant optical wave-packet that generated by conical superposition. The related results were published in Scientific Reports under the title of “Investigating group-velocity-tunable propagation-invariant optical wave-packets" on September 27, 2022.

The propagation-invariant optical wave-packet is also known as the diffraction-free optical wave-packet, whose spatiotemporal shape can remain unchanged during very-long-distance propagation much exceeding the Rayleigh length. A typical example is the Bessel-X optical wave-packet formed by the conical superposition of a Gaussian pulsed beam, which has already been widely used in medical diagnostics, biological imaging, micro-nano manufacturing, optical communications and so on. Due to two novel characteristics of a long propagation-distance and a superluminal group-velocity, this optical wave-packet recently has attracted more and more attentions from high-field laser physics. For example, it might realize the dephasing less laser wake-field acceleration and accordingly increase the electron energy significantly by increasing the acceleration-distance.

Previously, this research team has reported that, by separating the pulse-front of the input pulsed beam from its phase front and then modulating it into a required shape, the group-velocity of the optical wave-packet generated by conical superposition can be freely controlled. This work introduced the methods of generating superluminal, subluminal, and accelerating, decelerating, and arbitrarily-variable group-velocities; and in particularly, derived the equations and explained the mechanism in both the physical and the momentum (Fourier) spaces.

This work has provided the theory for generating group-velocity-tunable propagation-invariant optical wave-packets, which in future can be used in high-field laser physics, like the dephasing less laser wake-field acceleration.

Fig. Descriptions of a propagation-invariant optical wave-packet generated by conical superposition in the physical and the momentum spaces. (Image by SIOM)

Article website:
https://doi.org/10.1038/s41598-022-20601-0

Contact:
WU Xiufeng
General Administrative Office
Shanghai Institute of Optics and Fine Mechanics, CAS
Email: xfwu@siom.ac.cn
Web: http://english.siom.cas.cn/