Semiconductor ring lasers as optical neurons

Semiconductor Ring Lasers (SRLs) are a modern class of semiconductor lasers whose active cavity is characterized by a circular geometry. This enables the laser to support two counterpropagating modes, referred to as the clockwise (CW) and the counterclockwise (CCW) mode. Semiconductor ring lasers have been shown to have a regime of operation in which they are excitable, when the linear coupling between the counterpropagating modes is asymmetric. This can be achieved by increasing the reflection of, for example, the CW mode into the CCW mode. This will stabilize lasing in the CCW mode. In the excitable regime, the SRL will fire optical pulses (spikes) in the CW mode as a response to noise perturbations. In this contribution we experimentally and theoretically characterize these spikes. Our experiments reveal a statistical distribution of the characteristics of the optical pulses that is not observed in regular excitable systems. In particular, an inverse correlation exists between the pulse amplitude and duration. Numerical simulations and an interpretation in an asymptotic phase space confirm and explain these experimentally observed pulse characteristics [L. Gelens et al., Phys. Rev. A 82 063841, 2010]. We will also theoretically consider asymmetric SRLs coupled through a single bus waveguide. This is a first step towards an integrated optical neural network using semiconductor ring lasers as building blocks. We will show that for weak coupling, excitatory excursions still persist due to the similar phase space structure. Moreover, the coupled SRLs can excite pulses in each other and can thus function as communicating neurons [W. Coomans et al., Phys. Rev. E 84 036209, 2011]. This type of neural network can be fully integrated on chip and does not suffer from the drawback of needing extra-cavity measures, such as optical injection or saturable absorbers.

[1]  M. Sorel,et al.  Alternate oscillations in semiconductor ring lasers. , 2002, Optics letters.

[2]  Giacomelli,et al.  Experimental evidence of coherence resonance in an optical system , 2000, Physical review letters.

[3]  M Radziunas,et al.  Excitability of a semiconductor laser by a two-mode homoclinic bifurcation. , 2001, Physical review letters.

[4]  Miguel A. Larotonda,et al.  Experimental investigation on excitability in a laser with a saturable absorber , 2002 .

[5]  Paul R Prucnal,et al.  Ultrafast all-optical implementation of a leaky integrate-and-fire neuron. , 2011, Optics express.

[6]  J. Danckaert,et al.  Exploring multistability in semiconductor ring lasers: theory and experiment. , 2009, Physical review letters.

[7]  Delay-induced excitability. , 2004, Physical review letters.

[8]  J. Danckaert,et al.  Multistable and excitable behavior in semiconductor ring lasers with broken Z2-symmetry , 2010 .

[9]  Huug de Waardt,et al.  All fiber-optic neural network using coupled SOA based ring lasers , 2002, IEEE Trans. Neural Networks.

[10]  Marc Sorel,et al.  Excitability in optical systems close to Z2-symmetry , 2010, 1108.3738.

[11]  Gabriel B. Mindlin,et al.  Interspike Time Distribution in Noise Driven Excitable Systems , 1999 .

[12]  Giovanni Giacomelli,et al.  Andronov bifurcation and excitability in semiconductor lasers with optical feedback , 1997 .

[13]  J. Danckaert,et al.  Solitary and coupled semiconductor ring lasers as optical spiking neurons. , 2011, Physical review. E, Statistical, nonlinear, and soft matter physics.

[14]  J. Danckaert,et al.  Excitability in semiconductor microring lasers: Experimental and theoretical pulse characterization , 2010, 1108.3704.

[15]  J. García-Ojalvo,et al.  Effects of noise in excitable systems , 2004 .

[16]  M. Smit,et al.  A fast low-power optical memory based on coupled micro-ring lasers , 2004, Nature.

[17]  B Krauskopf,et al.  Excitability and coherence resonance in lasers with saturable absorber. , 1999, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics.

[18]  J. Danckaert,et al.  Topological insight into the non-arrhenius mode hopping of semiconductor ring lasers. , 2008, Physical review letters.

[19]  M Fischer,et al.  Excitable phase slips in an injection-locked single-mode quantum-dot laser. , 2009, Optics letters.

[20]  J. Danckaert,et al.  Two-dimensional phase-space analysis and bifurcation study of the dynamical behaviour of a semiconductor ring laser , 2008, Journal of Physics B: Atomic, Molecular and Optical Physics.

[21]  D Goulding,et al.  Excitability in a quantum dot semiconductor laser with optical injection. , 2007, Physical review letters.

[22]  Daan Lenstra,et al.  Multipulse excitability in a semiconductor laser with optical injection. , 2002, Physical review letters.