Recently, there has been tremendous interest in excitable optoelectronic devices and in particular excitable semiconductor lasers that could potentially enable unconventional processing approaches beyond conventional binary-logic-based approaches. In parallel, there has been renewed investigation of non-von Neumann architectures driven in part by incipient limitations in aspects of Moore’s law. These neuromorphic architectures attempt to decentralize processing by interweaving interconnection with computing while simultaneously incorporating time-resolved dynamics, loosely classified as spiking (a.k.a. excitability). The rapid and efficient advances in CMOS-compatible photonic interconnect technologies have led to opportunities in optics and photonics for unconventional circuits and systems. Effort in the budding research field of photonic spike processing aims to synergistically integrate the underlying physics of photonics with bio-inspired processing. Lasers operating in the excitable regime are dynamically analogous with the spiking dynamics observed in neuron biophysics but roughly 8 orders of magnitude faster. The field is reaching a critical juncture at which there is a shift from studying single devices to studying an interconnected network of lasers. In this paper, we review the recent research in the information processing abilities of such lasers, dubbed “photonic neurons,” “laser neurons,” or “optical neurons.” An integrated network of such lasers on a chip could potentially grant the capacity for complex, ultrafast categorization and decision making to provide a range of computing and signal processing applications, such as sensing and manipulating the radio frequency spectrum and for hypersonic aircraft control.

Recent progress in semiconductor excitable lasers for photonic spike processing

We report a first experimental study of the nonlinear dynamics appearing in a 1550 nm single-mode VCSEL subject to parallel and to orthogonal optical injection. For the first time to our knowledge we report experimentally measured stability maps identifying the boundaries between regions of different nonlinear dynamics for both cases of polarized injection. A rich variety of nonlinear behaviours, including periodic (limit cycle, period doubling) and chaotic dynamics have been experimentally observed.

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Nonlinear dynamics induced by parallel and orthogonal optical injection in 1550 nm Vertical-Cavity Surface-Emitting Lasers (VCSELs)

We report novel theoretical results obtained from combining the method of largest Lyapunov exponent (LLE) with the spin-flip model (SFM), including noise, to model a vertical-cavity surface emitting laser (VCSEL) subject to polarized optical injection. The LLE is applied to the numerical solutions in order to automatically calculate stability maps that characterize the dynamics. The SFM has been extended and generalized to allow for optical injection of arbitrary polarization. Measurements on a 1550-nm VCSEL have been used to estimate the values of key parameters for use in the model and with these we demonstrate excellent agreement between theory and experiment.

Dynamics of Polarized Optical Injection in 1550-nm VCSELs: Theory and Experiments

We report a new approach to mimic basic functionalities of a neuron using a 1550 nm Vertical Cavity Surface Emitting Laser (VCSEL) which is based on the polarisation switching (PS) that can be induced in these devices when subject to polarised optical injection. Positive and negative all-optical threshold operations are demonstrated experimentally using external optical injection into the two orthogonal polarizations of the fundamental transverse mode. The polarisation of the light emitted by the device is used to determine the state of the VCSEL-Neuron, active (orthogonal) or inactive (parallel). This approach forms a new way to reproduce optically the response of a neuron to an excitatory and an inhibitory stimulus.

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Optical neuron using polarisation switching in a 1550nm-VCSEL.

Effective Theory and Breakdown of Conformal Symmetry in a Long-Range Quantum Chain

We report the first experimental invetigation of the polarization-mode switching dynamics and injection-wavelength-dependent polarization-mode bistability of a 1.5-m wavelength single-mode vertical-cavity surface-emitting lasers (VCSELs) under external laser beam injection. An injection beam with polarization orthogonal to that of the stand-alone VCSEL caused polarization-mode instability and switching of the VCSEL output. By varying the optical injection detuning for fixed injection power observation was made of a novel form of polarization bistability which will have applications in a new type of all-optical flip-flop and signal processing scheme.

Optical Injection-Induced Polarization Switching Dynamics in 1.5- $\mu$ m Wavelength Single-Mode Vertical-Cavity Surface-Emitting Lasers

Low-Noise Single-Photon Detector for the 1.5-μm Wavelength Region

This paper reports a detailed experimental study of the Rayleigh backscattering e ects on singlemode bers (SMFs) fabricated by di erent vendors and on the quantum e ciencies of an InGaAs/InP single-photon avalanche detector (SPAD). An optimization process for the input laser power to achieve negligible backscattering-induced error in a plug-and-play type two-way quantum key distribution (QKD) scheme was determined for a SMF transmission of 25 km. Based on this process, we have demonstrated 2 kbit/s quantum interference counts with 1-MHz optical pulses transmitted over the 25-km SMF, which allows a 1-kbit/s raw quantum key generation based on the BB84 protocol to be enabled. The measured QBER was less than 3 %.

Rayleigh-Backscattering-Suppressed Two-Way Quantum Key Distribution

This paper represents, the first report of experimental observations of the polarization switching dynamics of a modulated 1.5-μm wavelength single-mode vertical cavity surface emitting laser (VCSEL) under optical injection control. An injected optical beam with polarization orthogonal to that of the stand-alone VCSEL caused a dynamical instability of the laser polarization state near threshold. Successful switching of the polarization state of the output of the VCSEL modulated at 5 MHz was achieved.

Kyu Hyeon Jeong

Papers

Optical Injection-Induced Polarization Switching Dynamics in 1.5- $\mu$ m Wavelength Single-Mode Vertical-Cavity Surface-Emitting Lasers

Low-Noise Single-Photon Detector for the 1.5-μm Wavelength Region

Rayleigh-Backscattering-Suppressed Two-Way Quantum Key Distribution

Injection-induced polarization switching of a modulated-1.5 μm wavelength single-mode VCSEL