QCLs exhibit extreme pulses

October 23, 2020

Extreme events occur in many observable contexts. Nature is a prolific source: rogue water waves surging high above the swell, monsoon rains, wildfire, etc. From climate science to optics, physicists have classified the characteristics of extreme events, extending the notion to their respective domains of expertise. For instance, extreme events can take place in telecommunication data streams. In fiber-optic communications where a vast number of spatio-temporal fluctuations can occur in transoceanic systems, a sudden surge is an extreme event that must be suppressed, as it can potentially alter components associated with the physical layer or disrupt the transmission of private messages.

Recently, extreme events have been observed in quantum cascade lasers, as reported by researchers from Télécom Paris (France) in collaboration with UC Los Angeles (USA) and TU Darmstad (Germany). The giant pulses that characterize these extreme events can contribute the sudden, sharp bursts necessary for communication in neuromorphic systems inspired by the brain's powerful computational abilities. Based on a quantum cascade laser (QCL) emitting mid-infrared light, the researchers developed a basic optical neuron system operating 10,000× faster than biological neurons. Their report is published in Advanced Photonics.

Giant pulses, fine tuning

Olivier Spitz, Télécom Paris research fellow and first author on the paper, notes that the giant pulses in QCLs can be triggered successfully by adding a "pulse-up excitation," a short-time small-amplitude increase of bias current. Senior author Frédéric Grillot, Professor at Télécom Paris and the University of New Mexico, explains that this triggering ability is of paramount importance for applications such as optical neuron-like systems, which require optical bursts to be triggered in response to a perturbation.

The team's optical neuron system demonstrates behaviors like those observed in biological neurons, such as thresholding, phasic spiking, and tonic spiking. Fine tuning of modulation and frequency allows control of time intervals between spikes. Grillot explains, "The neuromorphic system requires a strong, super-threshold stimulus for the system to fire a spiking response, whereas phasic and tonic spiking correspond to single or continuous spike firing following the arrival of a stimulus." To replicate the various biological neuronal responses, interruption of regular successions of bursts corresponding to neuronal activity is also required.

Quantum cascade laser

Grillot notes that the findings reported by his team demonstrate the increasingly superior potential of quantum cascade lasers compared to standard diode lasers or VCSELs, for which more complex techniques are currently required to achieve neuromorphic properties.

Experimentally demonstrated for the first time in 1994, quantum cascade lasers were originally developed for use under cryogenic temperatures. Their development has advanced rapidly, allowing use at warmer temperatures, up to room temperature. Due to the large number of wavelengths they can achieve (from 3 to 300 microns), QCLs contribute to many industrial applications such as spectroscopy, optical countermeasures, and free-space communications.

According to Grillot, the physics involved in QCLs is totally different than that in diode lasers. "The advantage of quantum cascade lasers over diode lasers comes from the sub-picosecond electronic transitions among the conduction-band states (subbands) and a carrier lifetime much shorter than the photon lifetime," says Grillot. He remarks that QCLs exhibit completely different light emission behaviors under optical feedback, including but not limited to giant pulse occurrences, laser responses to modulation, and frequency comb dynamics.
Read the peer-reviewed, open access research article: Olivier Spitz et al., "Extreme events in quantum cascade lasers," Adv. Photon. 2(6), 066001 (2020), doi 10.1117/1.AP.2.6.066001.

SPIE--International Society for Optics and Photonics

Related Neuronal Activity Articles from Brightsurf:

AI learns to trace neuronal pathways
Cold Spring Harbor Laboratory scientists dramatically improved the efficiency of automated methods for tracing neuronal connections.

Tone of voice matters in neuronal communication
Neuronal communication is so fast, and at such a small scale, that it is exceedingly difficult to explain precisely how it occurs.

Unbalanced microtubule networks launch establishment of neuronal polarity
Prof. MENG Wenxiang's group from the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences recently reported a new mechanism by which microtubule networks instruct neuronal polarity.

Protecting the neuronal architecture
Protecting nerve cells from losing their characteristic extensions, the dendrites, can reduce brain damage after a stroke.

Startled fish escape using several distinct neuronal circuits
A fast knee-jerk 'ballistic' escape response and a more considered 'delayed' escape response are mediated by distinct and parallel neuronal pathways in zebrafish, according to a study published October 15, 2019 in the open-access journal PLOS Biology by Harold Burgess of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, and colleagues.

How neuronal recognition of songbird calls unfolds over time
A novel computational approach sheds new light on the response of neurons in the brain of a songbird when it hears and interprets the meaning of another bird's call.

Up-close and personal with neuronal networks
Researchers from Harvard University have developed an electronic chip that can perform high-sensitivity intracellular recording from thousands of connected neurons simultaneously.

Stabilizing neuronal branching for healthy brain circuitry
Novel molecular mechanism may regulate microtubule stability, important for neuronal branching and potentially for nerve regeneration.

Discovery of neuronal ensemble activities that is orchestrated to represent one memory
The brain stores memories through a neuronal ensemble, termed engram cells.

Hidden dynamics detected in neuronal networks
Neuronal networks in the brain can process information particularly well when they are close to a critical.

Read More: Neuronal Activity News and Neuronal Activity Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.