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Slow light using cavity solitons in semiconductor resonators

Slow light using cavity solitons in semiconductor resonators. T. Ackemann, W J Firth , G L Oppo, A J Scroggie and A M Yao. SUPA and Department of Physics , University of Strathclyde, UK. willie@phys. strath.ac.uk. : INLN (Nice) – FIRST EXPERIMENT!. acknowledgements: FunFACS partners .

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Slow light using cavity solitons in semiconductor resonators

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  1. Slow light using cavity solitons in semiconductor resonators T. Ackemann, W J Firth, G L Oppo, A J Scroggie and A M Yao SUPA and Department of Physics, University of Strathclyde, UK willie@phys.strath.ac.uk : INLN (Nice) – FIRST EXPERIMENT! acknowledgements: FunFACS partners QEP17: Slow light using cavity solitons …

  2. All-optical buffers and delay lines • buffers can enhance performance of networks • future high-performance photonic networks should be all-optical • need for all-optical buffers with controllable delay Boyd et al., OPN17(4)18(2006)

  3. "Slow light" OR – Use small transversecomponent of light velocity - this talk Hau et al., Nature397, 594(1999) Boyd et al., OPN17(4)18(2006)

  4. Writing solitons in a vertical cavity • writing cavity solitons (CS) stores pulses indefinitely "stopped light" • an ideal homogeneous system has • translational symmetry •  ability to choose position in plane at will • in systems with translational symmetry translation is a neutral mode • no energy is needed for translation • any odd perturbation (gradient) couples easily to neutral mode and causes lateral drift "slow light" Saturable absorber model – Harkness et al., Strathclyde (1998)

  5. read out at other side all-optical delay line buffer register • time delayed version of input train All-optical CS delay line parameter gradient inject train of solitons here • for free: serial to parallel conversion and beam fanning • note: won‘t work for non-solitons/diffractive beams Saturable absorber model – Harkness et al., Strathclyde (1998)

  6. First experiments in semiconductors spatio-temporal detection system: 6 local detectors + synchronized digital oscilloscopes Bandwidth about 300 MHz • 920 µm VCSEL (Ulm Photonics) 200 µm diam: pumped above transparency but below threshold amplifier • pump "stripes" for quasi-1D • gradient along the stripes Spontaneous patterns and solitons mostly aligned to stripes. Home in on "soliton" in red ring. F. Pedaci, S. Barland, M. Giudici, J. Tredicce, INLN, Nice, 2006 (unpublished)

  7. optically addressed drifting structure delay  12 ns distance  25 µm velocity  2.1 µm/ns delay / width  2-4 superposition of 50 „CDE“ events:reproducible,solitonic Optical addressing gate addressing beam with an electro-optical modulator rise/fall times < 1 ns 100 ns F. Pedaci, S. Barland, M. Giudici, J. Tredicce, INLN, Nice, unpublished

  8. perturbative regime– linear in K • saturation: speed limit  1.5 µm/ns Velocity in experiment (and theory) • experiment suggests speed of about 2 µm/ns = 2 km/s (slow-ish!) • in line with theoretical expectations for VCSEL amplifier model: speed • E field, N carriers. J current, Pinput. • response ratio, small, ~ 0.01 • Pconstant amplitude, but constant phase gradientK. phase gradient K see also Kheramand et al., Opt. Exp. 11, 3612(2003)

  9. Comparison to other systems • slow light in the vicinity of resonances: electro-magnetically induced transparency, linear cavities, photonic crystals interplay of useful bandwidth and achievable delay 1Tucker et al., Electron. Lett. 41, 208 (2005); 2Dahan, OptExp13, 6234(2005); 3GonsalezHerraez, APL87081113(2005); 4ChangHasnainProcIEE911884(2003); 5Ku et al., OptLett29, 2291(2004); 5Hau et al., Nature 397, 594 (1999)

  10. K=0.0392 log(speed) Analytic (perturbation theory) and numerical dependences of drift speed vs(photon/carrier lifetimes)  ~ 10-2for carrier lifetime ~ 1 ns log() -2 4 0 2 Bandwidth and bit rate • observed velocity: 2 µm / ns; CS diameter typically 10 µm  • a local detector would see a signal of length 10 µm/(2 µm/ns) = 5 ns  bit rate 100 Mbit/s • limit: time constant of medium (carriers) 1 ns  10 µm/ 3 ns = 3.3 µm /ns

  11. time  space  10 carrier lifetimes: solitons independent 6 carrier lifetimes: solitons merge How close can cavity solitons be packed? Space-time plots of |E| for response ratio g=0.01, phase gradient K=0.471with different time delays between address pulses time  space  Simulation of VCSEL cavity soliton buffer with independent soliton "bits"

  12. Solitons are pretty robust against gradient Soliton for K=0.471, g=0.01 – large gradient, modest distortion – and some asymmetry Soliton for K=0.0196, g=0.01– small gradient, little distortion

  13. Résumé: CS-based delay line • drifting CS are a novel approach to slow lightwith promising features • potentially very large delays with good figure of merit • lots of things to do • theory: saturation behaviour Auger etc. patterning effects • fabrication: homogeneity, built-in gradients • experiment: control gradients, improve ignition, larger distances ... • in a cavity soliton laser1 there are additional possibilities • relaxation oscillations are faster than carrier decay time and modulation frequency of modern SC lasers is certainly faster (at least 10 Gbit/s) • possibility of fast spontaneous motion (Rosanov, 2002) 1FunFACS project objective

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