Sunday , November 29 2020

PC Revue | An oscillating mirror allows physicists to pierce a laser hole into space



Lasers can now achieve petawatt power. If you focus such a powerful laser beam on a small space, everything will be destroyed, the thing will fall apart, leaving only the electrons and nuclei. However, laser physicists did not stop there. Under good experimental conditions, the structure of space and time explodes and the quantum patterns stretch to fracture. And all we need is a new kind of mirror.

Humanity now uses about 18 TWh of energy. Petawatt is 1000 times more than terawatt. The most powerful laser currently produces energy in the range of 5 to 10 petaetates. But it is set to reach 100 petawatts in the near future. Current lasers produce 5 – 5,000 J of energy for a very short time (between picoseconds, 10 sec-12 s, and a few femtoseconds, which is 10-15 p). However, at this stage the energy flow is huge. And the numbers are even more amazing when you notice that all the energy is aligned so that the bar produces energy 1022 W / cm2.

However, physicists strive to achieve up to 10 energies29 W / cm2. But when the intensity exceeds 1025 W / cm2if the light hits only one electron, there is enough energy to trigger the generation of the positron electron cascade from the vacuum. At 10 o'clock29 W / cm2 no more electron needed – light pulls virtual electrons from vacuum. So the laser breaks reality and generates real charges from the seemingly empty void.

But get to 1025 W / cm2 it is difficult. The main issue is the material, or rather the lack of material, which may persist long enough to target the laser beam as needed. And here comes the plasma mirror. They have been around for a long time and this idea is really very simple.

Plasma is a gas formed by electrically charged particles in which free electrons move. When light (laser) hits the plasma, the electrons accelerate the movement by absorbing the light and radiating it in the opposite direction. The light is reflected from both the plasma and the chrome bumper of the car. The laser beam cannot destroy plasma because plasma is essentially destroyed mass.

It was originally assumed that plasma mirrors could not function as a good focusing element because they do not retain the correct shape. But with the help of a supercomputer, it has been shown that a plasma mirror can be the way to go. French scientist Henri Vincenti has found new ways to increase the intensity of a very powerful laser beam. His model uses a vibrating plasma mirror, the surface of which is angled with a laser beam.

First, the plasma mirror is created with a less energetic laser pulse and then used to create an extreme beam of energy. Pulse duration decreases from 20 femtoseconds to 0.1 femtoseconds, which in itself increases the intensity by a factor of 100. A shorter wavelength means that the laser focuses at a smaller point. The result of the incremental laser intensity increase is a factor of 1000.

But can it really work? The technical details don't seem difficult – with a low energy terawatt laser pulse, you can create a mirror and hit whatever you have a few picoseconds later. And then everyone can wonder the hole you've made.

The study was published in the journal Physical review letters.

Source: arstechnica.com.

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