Will read the paper later. It's interesting and the PIC sims which are state of the art seem interesting, I really want to know how resilient the focusing effect is to laser beam imperfections because that has been the bane of every experiment pushing the high intensities over the last few years.
The idea iterates from a hot topic in intense laser plasma physics, an already niche within a niche of fields. The idea is a "Plasma Mirror." In the world of high intensity laser physics which means lasers essentially more intense than 1e14 W/cm^2 ( by comparison, sunlight at the earth's distance from the sun is ~0.1 W/cm^2) and such, they very quickly ionize the matter they interact with. The lasers where "Plasma Mirrors" are relevant are even more intense than this, say 1e16 and above. However, given you are playing with high magnitude orders of intensity, you have long tails of intensity before the peak of the pulse that are a few orders down (say, 1e14 W/cm^2) but are intense enough to damage the target you want to interact with. The idea is to have a thin target of something before the main target in the optical path which acts as a shutter. The idea is such, the probability in high field laser physics of ionization essentially approaches one the higher the intensity of the incident light. The thin target, called a plasma mirror, permits more low intensity light below some threshold and starts to ionize when the intensity ramps up well above 1e14, turning into a very good mirror. The effect is it only reflects the higher intensity light, creating a cleaner, shorter pulse of high intensity laser energy.
The second concept seems to be the geometrical shape of plasma mirror. I think this is the new idea, because plasma mirrors have been here for a while. The idea here seems to either statically or dynamically shape the plasma mirror so it also focuses the light. I believe the record for high intensity is 2e22 W/cm^2. There are plans to create a near 1e24 W/cm^2 facility in Europe. The sims here suggest an intensity of 1e25 W/cm^2, which is interesting for a number or reasons, because it is near the point where this field starts to touch strong field quantum effects, still a few orders down but approaching the strong field region of QED.
To be critical, as usual, these are simulations, which is fine, but it will be important to see how what physics they included in their simulations. Recent literature has shown the traditional methods we use to model this physics starts to break down as we increase the intensity of the laser above 1e24 or so.
4000^3 cells is extremely large for a PiC simulation and the dispersion free Maxwell solvers are indeed state of the art (without them this simulation would be impossible and scaling those solvers is quite hard), but the 2 particles per cell is worryingly low, even for a 3d simulation with high order particles. Right now I can not read the supplemental material so I am not sure to which degree this was validate with more particles in2d, but if nature does not behave like this simulation, that is going to be the reason.
One application (which I used to work on) is generating electric field strengths beyond the 'Schwinger limit'. This is a field strength below which various QED processes are exponentially damped, such as electron-positron pair production. Generating such field strengths in the laboratory (as opposed to, say, the surface of pulsars) will allow studies of strong-field QED.
Actually no, the "photonuclear" region is actually already achieveable, the issues in that field are more mundane/engineering related, often how to increase efficiency, how to make things repeatable instead of 5 shots per week, etc. 1e25 W/cm^2 is approaching the next frontier, the strong field quantum regime.
Best bet I got is a reference to the book "Seveneves" which uses a nuclear reactor buried in primarily ice asteroid. They consume the ice and use steam essentially as a propellant.
Basically, a rocket that's 100% propellant, no onboard energy. Use the laser to a melt the ice and create a cometary-like exhaust trail, e.g. a purely ablative rocket.
The idea iterates from a hot topic in intense laser plasma physics, an already niche within a niche of fields. The idea is a "Plasma Mirror." In the world of high intensity laser physics which means lasers essentially more intense than 1e14 W/cm^2 ( by comparison, sunlight at the earth's distance from the sun is ~0.1 W/cm^2) and such, they very quickly ionize the matter they interact with. The lasers where "Plasma Mirrors" are relevant are even more intense than this, say 1e16 and above. However, given you are playing with high magnitude orders of intensity, you have long tails of intensity before the peak of the pulse that are a few orders down (say, 1e14 W/cm^2) but are intense enough to damage the target you want to interact with. The idea is to have a thin target of something before the main target in the optical path which acts as a shutter. The idea is such, the probability in high field laser physics of ionization essentially approaches one the higher the intensity of the incident light. The thin target, called a plasma mirror, permits more low intensity light below some threshold and starts to ionize when the intensity ramps up well above 1e14, turning into a very good mirror. The effect is it only reflects the higher intensity light, creating a cleaner, shorter pulse of high intensity laser energy.
The second concept seems to be the geometrical shape of plasma mirror. I think this is the new idea, because plasma mirrors have been here for a while. The idea here seems to either statically or dynamically shape the plasma mirror so it also focuses the light. I believe the record for high intensity is 2e22 W/cm^2. There are plans to create a near 1e24 W/cm^2 facility in Europe. The sims here suggest an intensity of 1e25 W/cm^2, which is interesting for a number or reasons, because it is near the point where this field starts to touch strong field quantum effects, still a few orders down but approaching the strong field region of QED.
To be critical, as usual, these are simulations, which is fine, but it will be important to see how what physics they included in their simulations. Recent literature has shown the traditional methods we use to model this physics starts to break down as we increase the intensity of the laser above 1e24 or so.