The first observation of Broglie-Mackinnon wave packets was achieved using the probability drop theorem of the 1980s.

Researchers at the University of Central Florida College of Optics and Photonics have achieved the first observation of Broglie-Mackinnon wave packets by taking advantage of a 1980s-era theorem in laser physics.

A CREOL research paper with Florida Photonics Center of Excellence professor Ayman Abouraddy and research associate Layton Hall has been published in the journal. Natural Physics.

Observation of optical de Broglie–Mackinnon wave packets highlights the group’s research using a group of pulsed laser beams that they call space-time packets.

Interview with Dr. Abouraddy, provides more insight into his team’s research and what the future holds.

You have completed several ‘firsts’ during this phase of your research. Will you give a history of the theoretical ideas that brought you there?

In the early days of the development of quantum mechanics nearly 100 years ago, Louis de Broglie made the important breakthrough of distinguishing waves from particles, sometimes called wave-particle duality . However, an important issue was not resolved. Particles are fixed in space: their size does not change as they move, however waves change, spreading out in space and time. How can one make a model from the waves proposed by de Broglie that nevertheless correspond exactly to a particle?

In the 1970s, L. Mackinnon proposed a solution by combining Einstein’s special theory of relativity with de Broglie waves to create a stable ‘wave packet’ that does not propagate and therefore can travel with a particle moving. This suggestion was not noticed because there was no way to generate such a wave packet. In recent years, my group has been working on a new class of pulsed laser beams that we call ‘space-time wave packets,’ which travel rigidly in free space.

In our latest research, Layton extended this behavior to spread in dispersive media, which usually stretches optical waves—except for packets of spatial waves that oppose this stretching. He noted that the propagation of space-time wave packets in space with a special type of dispersion (so-called anomalous dispersion) is consistent with Mackinnon’s proposal. In other words, space-time wave packets hold the key to finally achieving de Broglie’s dream. By performing laser experiments on these pathways, we observed for the first time what we called Broglie-Mackinnon wave packets and confirmed their predicted properties.

What is unique about your results?

There are several unique features of this paper. This is the first example of an incredibly stable pulse propagation. In fact, the most famous theory of laser physics from the 1980s proves that such an action cannot happen. We found a loophole in that study that we used when designing our optical systems.

Also, all previous pulsed fields that propagate without change are X-shaped. It has long been thought that constant wave packets in the shape of O should exist, but they have never been seen. Our results reveal consistent O-shaped wave packets.

The US Office of Naval Research supports your research. How is what you found useful to them and others?

We don’t know for sure yet. However, these findings have practical implications for the propagation of optical waves in dispersive media without having a negative impact on scattering.

These results may pave the way for optical experiments of the solution of the Klein-Gordon equation for large particles, and may even lead to the integration of non-dispersive wave packets using matter waves. This could also enable new sensing and microscopy techniques.

What are the next steps?

This work is part of a larger study of the propagation characteristics of space-time wave packets. This includes the propagation of long-wavelength packets that we are experimenting with at UCF’s Townes Institute Science and Technology Experimentation Facility (TISTEF) on the Florida coast. From a basic perspective, the optical system we used in our experiments is located in a closed path. This has not been achieved before, and opens the way to study the topological structures of light on closed surfaces.