Light bullets with highly controllable velocities
A research group of the Institute of Laser Engineering of Osaka University has theoretically generated spatiotemporal optical wave packets, known as "linear light bullets," in free space, by deforming the pulse-front of optical pulses and keeping the phase-front unchanged.
Light bullets, or three-dimensional spatiotemporal solitons, are high-intensity optical wave packets and are used in a wide range of applications. According to Einstein’s theory of relativity, the speed of light in free space is constant and cannot be exceeded, but it is possible to control the group velocity of optical pulses.
In previous study of this group (Scientific Reports DOI:10.1038/s41598-020-68478-1), the researchers created a straight-line propagation light bullets with freely tunable velocity and acceleration. However, the problem was that only one determined motion form, for example, superluminal or subluminal for velocity and accelerating or decelerating for acceleration, could be achieved in a single propagation path.
In this study, using their spatiotemporal coupling method, the group theoretically generated group velocity and acceleration tunable 3D optical wave-packets in free space. The group velocity of the optical wave-packet in free space or in transmission materials was controlled, including all motion forms, such as superluminal, subluminal, accelerating, decelerating, and backward-propagation.
Using this method, they generated 3D laser light bullets with highly controllable velocities and the light bullets had different motion forms: arbitrarily-variable velocities (and accelerations) during a single propagation path, which is not against Einstein’s theory of relativity.
Since the pulse-front of optical pulses can be controlled, the velocity of light bullets in a single propagation path can also be controlled. Using this group's spatiotemporal coupling method, it is possible to generate light bullets with arbitrarily-variable or -controlled velocities. This non-diffraction light bullet with nearly-programmable flying velocities will enable a wide range of applications, such as micromanipulation of small particles or objects according to speed, bio-imaging, particle acceleration and manipulation, radiation generation.
If the flying velocity of laser light bullets is controlled, it will become possible to match the frequency of the electromagnetic field generated from laser light bullets and the frequency of flying electrons, so it will improve the efficiency of electron acceleration.
The article, “Optical wave-packet with nearly-programmable group velocities,” was published in Communications Physics at DOI: https://www.nature.com/articles/s42005-020-00481-4.
Related links
Power Laser System Group, Institute of Laser Engineering, Osaka University (link in Japanese)
