In recent years, scientists have started working on the concept of anti–laser, which are devices that perfectly absorb light of a specific wavelength instead of emitting light from a typical laser.
Now, researchers have published a study exploring the idea of a blueprint for anti–laser construction, which is more complex than anything we’ve seen before.
More than an anti–laser, this team’s device is a “random anti–laser;” that is, a device capable of absorbing randomly scattered waves in all directions. This capability has a variety of potential uses, from telephone antennas to medical devices, anywhere that requires the capture of waves.
An anti–laser may sound crazy, but it’s more than what’s on the label. You can think of the working principle of such a device as the reverse of laser light pulse; to be absorbed rather than irradiated. Anti–lasers have only been realized in one–dimensional structures where the laser light is directed in opposite directions. But the approach in this study is more general; it has been shown that systems of arbitrary complexity in two or three dimensions can perfectly absorb the wave of the appropriate structure. This unique concept can be used for applications on an even larger scale with this method.
The versatility and flexibility of this device set it apart from previous similar devices. The team used a series of calculations and computer simulations to theorize how this flawless device would work, backed up by physical lab testing. The key to a perfect absorption process is to find a wave surface in the incoming signals. This makes it possible to absorb waves that do not come from predictable ways but scatter waves from many different sources.
Waves scattered in intricate patterns abound around us; for example, cell phone signals are reflected before reaching your phone. This multiple scattering has practical use in random lasers. Such exotic lasers are based on disordered environments with a random internal structure that can trap light and emit it into a complex, system–specific laser field when energized.
When it came time to build their anti–laser, the scientists assembled a series of randomly placed Teflon cylinders and sent microwave signals to scatter over them. Just like water waves bouncing off rocks in a pond. A waveguide with an antenna in the center was placed on it to absorb incoming waves. The researchers managed to absorb 99.8% of the signals they broadcast. This high rate is still among tightly controlled conditions. The team first measured wave reflections as they arrived in fine–tune the central antenna to absorb the signals. Both the signal frequency and the absorption power had to be carefully calibrated.
Considering this is still the first attempt, it is very promising. The theoretical physics behind the project predicts that this process could be adapted to a wide range of other signals and applications.
This system can be applied to any scenario where waves must be perfectly focused, directed, and absorbed. For example, you can set the cell phone signal so that your cell phone antenna can perfectly absorb it. In addition, various applications can be encountered in the medical field where wave energy is directed to a particular point, for example, as shock waves on kidney stones.