1. Fun.F.A.C.S. Meeting Como, 28-29 Spetember 2005 CNR-INFM: Como: L.A.Lugiato, F.Prati, G.Tissoni, L.Columbo, G.Patera Bari: M. Brambilla, T. Maggipinto, I.Perrini, SPECIFIC TARGETED RESEARCH OR INNOVATION PROJECT

2. Advances (March-Sept.): - Cavity Light Bullets - Semiconductor model, non-MFL approach Role of carrier dynamics, self-confinement - MQW model with inclusion of the WL-QD dynamics - MI analysis, pattern & CS simulations, link with growth/experiment

3. Passive case

5. Active case

6. Using the indications of the 3-D LSA we study the system dynamics. For this highly demanding computational task a parallel code was developed. Beyond the Mean Field Limit: semiconductor model (Passive)7 1) Neglect transverse diffusion (longitudinal diffusion (luckily) avoided in MQW samples) 2) Start from parametric regimes close to those where self-confinement existed in SatAbs 3) Search for the usual conditions, heuristically favourable for patterns/CLBs Boundary conditions Radical caveat: carrier slow dynamics hinders the longitudinal self- confinement

7. Self-focusing parametric regime  e =-2,  0 =-0.4,  =-20, T=0.1 and  =50.0  300.0 Longitudinal filaments …… Stationary state curves Longitudinal filaments  ~300  17.011.0 9.0 Y x z Near field Transient!

8. 1) No phenomena of spontaneous structure localization in the propagation direction 2) But it turns out that a longitudinally confined portion of a longer filament (snippet) is an in. cond. leading to a stable self-localised solution (e.g. for 1500 t.u) and for a large range of input field values …but self confinement can be found… x z x z Near field Far field

9. 9.65 t.u.1.3 t.u. 0.35 t.u. x z …to  ~100s …and the CLB can be switched on ! Shooting the usual addressing pulse ~1 t.u.

10. I II Univ. of Strathclyde How can we reach viable parametric regimes ? - The carrier dynamics is governed by the rate - So one can think of using longer media (edge emitters?) - Use an extended cavity, possibly pumped L A <<l Semiconductor sample Input mirrorOutput mirror  LALA EiEi ETET

11. Perspectives and open issues - Search for spontaneous self-confinement - Control pulse for CLB enconding (intensity, duration etc.) - Beat sloth

12. MQD microcavity model refinement (from Barbay et al. IEEE JOB 2003) Other than the inhomogeneously broadended QD resonance [Barbay et al. IEEE JOB 2003], new coupling mechanisms are considered between the Wetting Layer and the QD : 1. Thermoemission and capture of a carrier directly between a dot level and the WL continuum 2. Auger processes between the WL and the dot, involving 3 particles. Since we do not pump into the WL, N WL is low and we can retain only the Auger terms at first order in N WL Scope: guide and validate development of sample and experiments on CS at LPN A 2D hole is captured by the QDs due to Coulomb interaction with a previously captured 0D electron; the latter is excited from the QDs into the WL [See A. V. Uskov, J. McInerney, F. Adler, H. Schweizer and M. H. Pilkuhn, Appl. Phys. Lett. 72, 58 (1998)]

13. The model equations: field, carrier occupation probabilities in the quantum dots, carrier density in the wetting layer Inhomogeneous broadening QD capture & thermoemisson Auger QD-WL processes Carrier pumping in the WL (initiated)

14. Study of modifications in the SS curve - Auger effects w/out pump are modest - Comparable hysteresis cycles - High capture, low escape rates offer best conditions - Realistic case: hole confinement weaker than electron’s “Focusing” case“Defocusing” case The MI and bistability ranges suitable for finding stable CS, remain within viable parametric conditions w/respect to growth feasibility

15. Pattern analysis shows extended CS branches « Defocusing » case « Focusing » case PERSPECTIVES: - Study of parametric cases that will be inferred from the ongoing experiments on devices (see the poster by LPN) - Analysis of the model in the case of carrier pumping in the WL (optical/electrical) - In the former case, one must inspect the role of WL-QD interaction processes of higher order in N WL, and the role of other phenomenologies (e.g. bandgap renormalization and Coulomb interactions) Paper submitted to Applied Physics B (Special Issue), available on private area at www.funfacs.org The inclusion of QD-WL interactions maintain Patterns & CS close to the exp.lly viable ranges, as already evidenced in the former approach [Detunings (cavity and inhom. carrier distribution), C, driving field intensities...]