Ultrafast laser-pulse-driven electronics could be on the horizon, as a collaborative team of researchers from Canberra and Saudi Arabia have created a low-cost nanoscale laser source.
The reinvented laser source stores light energy inside nanoscale disks, then uses those interactions to generate high-speed pulses of light on microchips. They could be the basis of optically powered neurocomputers.
The partnership included Yuri Kivshar's group at the Australian National University and Andrea Fratalocchi, an Associate Professor of Electrical Engineering at the King Abdullah University of Science and Technology (KAUST).
Photonic devices that use controlled laser pulses to manipulate data switches, biomedical implants and solar cells are a lot faster compared to traditional electronics. However, a major limitation is the difficulty associated with making lasers small enough to fit onto computer circuit boards, while also retaining pulse-shaping capabilities.
"The challenge of reducing an optical source down to the nanoscale is that it starts to emit energy strongly in all directions," explained Fratalocchi. "This makes it almost impossible to control."
The solution lay with unconventional anapole lasers. These types of lasers are made from semiconductors shaped into precisely sized nanodisks, and they respond to light stimulation by producing electromagnetic waves that either radiate or rotate in donut-shaped toroid distributions.
At specific frequencies, the interference between the two fields produces the anapole state, which does not emit energy in any direction, but rather traps the light inside the nanodisk, storing it until it is needed.
“You can think of this laser as an energy tank—once the laser is on, it stores light and doesn’t let it go until you want to collect it,” said Fratalocchi.
Using quantum-based algorithms, the researchers simulated various engineering architectures using this new light source. These calculations predicted that anapole nanolasers can generate ultrafast light pulses that are suitable for studying natural patterns of signalling and neural connections.
The nanolasers appear invisible until it is stimulated by a nearby object. It is also possible to arrange the light sources into a loop, to produce a chain reaction of light emissions, tuneable down to femtosecond pulses.
"It’s really like a population of fireflies, where the individuals synchronize their emissions into beautiful patterns," Fratalocchi explained "When we place the nanolasers close together, we can get similar control over the pulses."
The team’s models suggest that integrating different loops of anapole nanolasers may produce oscillating, dynamic patterns useful for reproducing brain-like activities, such as machine learning and memory retrieval at low cost because the platform needs only inexpensive silicon wafers to work.