Synopsis: Semiconductor Lasers Get Nervy

Semiconductor lasers can exhibit characteristics of nerve cells, making them potentially useful for simulating biological neural networks.
Synopsis figure
F. Selmi et al., Phys. Rev. Lett. (2014)

The brain’s information processing ability has inspired researchers to build neuromimetic computing systems from building blocks that behave like neurons. To accurately mimic neural behavior, these individual units should exhibit the characteristic of so-called excitable media, like axons—appendages that transmit impulses away from the body of neuron cells: Axons respond to a stimulus below a threshold with small, linear responses; above threshold, they respond with a large nonlinear response. Essential to their operation is a refractory period following the nonlinear events, during which any response is temporarily inhibited.

In a paper in Physical Review Letters, Sylvain Barbay and colleagues at the CNRS Laboratoire de Photonique et de Nanostructures in France, demonstrate that semiconductor lasers can reproduce the refractory period of an excitable system and thus could form the basis of optical computing architectures. The researchers studied the response of a micropillar laser with an intracavity saturable absorber (a material that blocks low-intensity light but allows high-intensity light through). The micropillar laser is pumped continuously just below threshold while another laser provides pulses that push the excitation above threshold. The response stimulated by such pulses is measured via the microlaser emission.

By using pairs of pump pulses with varying delay, the researchers were able to map out the refractory period, which consists of an “absolute” portion for delays less than 200 picoseconds (no response at all to the pump pulse) and a “relative” portion between 200 and 350 picoseconds (the response begins to recover). The confirmation that the micropillar laser with saturable absorber is an excitable system with an absolute and relative refractory period may lead to its use in a variety of optical neural networks. – David Voss


Features

More Features »

Announcements

More Announcements »

Subject Areas

OpticsBiological Physics

Previous Synopsis

Related Articles

Focus: A Tiny Engine Powered by Light and Liquid Physics
Statistical Physics

Focus: A Tiny Engine Powered by Light and Liquid Physics

A micrometer-sized sphere trapped by optical tweezers in a liquid, under the right conditions, orbits rapidly around the laser beam—creating a potential micromixing device. Read More »

Viewpoint: Intense Laser Sheds Light on Radiation Reaction
Plasma Physics

Viewpoint: Intense Laser Sheds Light on Radiation Reaction

Experimentalists have used ultraintense laser light to explore a fundamental problem in quantum electrodynamics: the response of an accelerated electron to the radiation it emits. Read More »

Synopsis: How Hairy Tongues Help Bats Drink Nectar
Fluid Dynamics

Synopsis: How Hairy Tongues Help Bats Drink Nectar

Experiments and theory show that hairs on a bat’s tongue allow the animal to drink 10 times more nectar than it could if its tongue were smooth. Read More »

More Articles