Scientists have built a laser platform established on a network resembling a spider’s web, which can be accurately regulated to generate diverse light colors.
The platform, invented by a team guided by scientists at Imperial College London with partners in Switzerland and Italy, could be employed in new computing and sensing applications. The team is already working along with research and industrial partners throughout Europe to analyze applications in machine learning.
In conventional lasers, light rebounds between two mirrors in a material that intensifies the light until it touches a specific threshold. Laser light is created in narrow beams that are stable across long distances. However, the light is typically only generated in a single frequency, equivalent to a single color.
Network lasers function differently and are composed of a mesh of nanoscale optical fibers merged to develop a web-like network. Light passes along the fibers and disturbs them in such a way as to yield hundreds of colors instantaneously. However, the colors are blended complexly and released haphazardly in all directions.
In a new study published in Nature Communications, researchers have formulated a technique to regulate a network laser so that it only releases a single color or combination of colors at one time. The platform irradiates exclusive ‘illumination patterns’ on the network laser, with each precise pattern prompting a combination of laser colors or a diverse laser color.
The illumination patterns are formed using a digital micromirror device (DMD), a computer-regulated device with thousands of mirrors. The DMD is enhanced by an algorithm that chooses the most favorable pattern for a specific laser color.
The researchers state the new network laser systems could have numerous applications, mainly as they can be incorporated into chips. For example, they could be employed as very secure hardware keys, where the illumination patterns become the secure keys that produce the password in the form of the laser spectrum.
Since the lasers are also extremely sensitive to precise illumination patterns, the network lasers could be employed as sensors that can monitor even small variations on adjacent surfaces.
The system is the outcome of a five-year partnership between Imperial’s Departments of Mathematics and Physics, organized by postdoctoral researchers Alexis Arnaudon and Dhruv Saxena, one in each department. The researchers created tools to enhance the illumination patterns based on physical modeling and theory and showed them in action.
Maths and Physics Coming Together
Professor Riccardo Sapienza, a co-author of the study from the Department of Physics at Imperial College London, said: “We have combined the mathematics of network theory with laser science to tame these complex lasers. We believe this will be at the heart of light processing on chips and we are testing it now as a machine learning hardware.”
This is an example where we saw maths and physics coming together, showing how the properties of a network can affect and help control the lasing process. The next big challenge is to design networks and illumination patterns to control the temporal profile of the laser light and encode information in it.
Mauricio Barahona, Study Co-Author and Professor, Department of Mathematics, Imperial College London
The scientists are part of the EU Horizon 2020 project CORAL (COntrolling network RAndom Lasers on chip), along with IBM Zurich, to push the forthcoming field of network lasers toward commercialization. The UK EPSRC also funded the study.
Saxena, D., et al. (2022) Sensitivity and spectral control of network lasers. Nature Communications. doi.org/10.1038/s41467-022-34073-3.