What a Laser Bullet Would Actually Look Like

In the 1960s and 70s, lasers weapons were science fiction's lethal force of choice. The prime examples are, of course, the Star Wars movies, where colorful neon beams allowed for a bloodless cartoon envisioning of space violence.

Laser weapons are mostly a nostalgia trip now, as latter-day gritty realism has taken over much of the sci-fi genre and, well, weaponized lasers just aren't very realistic. Or, rather, weaponized laser sidearms don't seem very realistic. A group of Polish researchers decided to ask, what if laser bullets were real? What would that look like?

The group's task was to make a video of the traveling laser bullet, with the goal of recreating the slow-speed laser pulses of the sort depicted in the Star Wars trilogy. That's the catch with laser bullets in the first place: They would be travelling too fast to actually film.

As such, no one really knows what a laser bullet would look like or how exactly it might behave. We can snag images of conventional bullets mid-flight using super-high-speed photography, but not so much laser pulses. "If you wanted to film a single light impulse to move as slowly on film as in our recording, you would have to use a camera operating at a speed of a billion frames per second", said Dr. Yuriy Stepanenko, the Polish team's lead researcher, in a statement. That camera doesn't exist.

So, instead of trying to film individual laser bullets, the researchers captured individual images of different light pulses at different points along the laser's path (which was the same for all of the recorded pulses). The video actually shows many different (yet identical) laser pulses, but the effect is the same as if it were just one.

"Luckily, the physics always stays the same," explained Paweł Wnuk, another member of the Polish team. "So, on the film one can observe all the effects associated with the movement of the laser pulse in space, in particular, the changes in ambient light depending on the position of the pulse and the formation of flares on the walls when the light passes through the dispersing cloud of condensed water vapor."

An interesting feature of blasting high-energy laser pulses through the normal ambient atmosphere of Earth (or anywhere else with breathable air) is that the pulses interact with the air itself in very significant ways. Any atoms standing in the way of the beam will find themselves very quickly ionized, a process that releases energy. The result of this ionization is that a filament of high-energy plasma forms next to the actual pulse.

There's an energy threshold below which the beam, as it collides with atoms in the ambient air, becomes dispersed and basically just falls apart. Above that threshold, it becomes possible to "tune" the frequency and duration of the laser bullet such that the electromagnetic field of the pulse itself and plasma work together to effectively self-focus the beam as it travels. Thus, it doesn't disperse.

The beam itself is a notable and fairly recent advance. Developed by the same Polish team, it's capable of producing 10 terawatts of power in femtosecond pulses (millions of a billionth of a second), from a device occupying the space of a half-desktop. It probably won't be knocking any stormtroopers off their feet just yet, but future upgrades hope to boost its power upwards of 200 terawatts, where it will be useful for blasting cancer cells, at least.