Fire the Laser!

When lasers and explosions are combined, the first thing that may come into most people’s mind is that they’re only capable of destroying things – but not in the case of some ANU scientists! A team from the ANU Research School of Physics and Engineering have created a (literally) explosive new technique, which can be used to make new material structures, by simply shooting stuff with a laser. But we’re not just talking about any old laser here; rather a specific laser known as the Femtolaser, which can fire around 10 trillion pulses per second.

As discussed in their paper, published in Nature Communications, these rapid laser pulses cause micro explosions to occur in the material being shot at. This puts the material (in this case silicon), under intense pressure causing the material to be heated up to 100,000 degrees celsius. That’s more than 15 times hotter than the surface of the Sun. This incredible heat and pressure causes the silicon to turn into a weird plasma state known as Warm Dense Matter (WDM)- a state that is too energetic to be solid but too dense to be normal plasma.

In this state, the material’s previous structure is wiped away and the atoms can rearrange themselves into new patterns and structures. As a result the new version of the material has very different properties to what is normally observed.

These new structures tend to be unstable and would disappear after a short period of time, but fortunately the material is able to cool incredibly quickly (thanks to the Square-Cube Law); literally freezing the atoms of the material in these new arrangements after a fraction of a second.

Perhaps the most interesting aspect of this process by far is the different properties that the resulting material structures have. For example, one structure has significantly higher absorption rates of light, meaning that it could be used to create highly efficient solar cells which can be used to produce electricity.

Another potential structure is that of a superconductor – a material that has no electrical resistance. Superconductors have a huge range of applications, ranging from medical technology such as MRI machines, cutting edge high speed transportation (like Maglev Trains) and high speed computing. The semi-conductor industry in computers alone is worth billions of dollars, meaning that making semi-conductors which are also superconductors could have a massive impact on this industry (and as a bonus could stop computers from generating excess heat).

These sorts of materials aren’t new, we’ve been making them for years. But normally we use tiny diamond tipped hammers to smack the material, creating high pressure and temperature to achieve a similar effect. However this method produces temperatures and pressure much lower than the new technique, and as a result is nowhere near as effective. The laser-explosion technique can create thousands of “microzones” (areas with new structure) in a material every second, which is far more than any diamond hammer.

Most importantly, the laser-explosion technique is far cheaper and easier to upscale for industrial scale manufacturing, meaning that we could potentially manufacture larger amounts of better quality materials, for a fraction of the current price.

So you could one day be using your high speed, heat free computer while riding on a high speed maglev train (both of which are powered through super solar cells) thanks to the work of this team of ANU scientists!