1. Jianke Yang Dept of Mathematics and Statistics, University of Vermont Igor Makasyuk, Anna Bezryadina, Zhigang Chen Dept of Phys. & Astronomy, San Francisco State University Dipole and Vector Solitons in 2D Photonic Lattices

2. Discrete solitons in waveguide arrays D. N. Christodoulides et al.,, Optics Letters 13, 794 (1988). H. S. Eisenberg et al.,, Physical Review Letters, 81, 3383 (1998).

3. Optically-induced lattices in photorefractive crystals v SBN Efremidis et al., PRE 2002 Fleischer, et al., PRL, Nature 2003 Nashev, et al., OL 2003 From multiple o-beam interference Linear waveguides Spatial modulation of a partially coherent o-beam O-beam E-beam Amplitude mask Chen, et al. PRL2004

4. So far, fundamental and vortex solitons in a 2D lattice have been reported: Fleischer, et al., PRL, Nature 2003 Martin, et al., PRL 2004 Malomed and Kevrekidis, PRE 2001 Yang and Musslimani, OL 2003 Neshev, et al., PRL 2004 Fleischer, et al., PRL 2004 Yang, New J. Phys. 2004

5. In this talk, we report both theoretically and experimentally dipole and vector solitons in a 2D photonic lattice

6. Dipole solitons in a 2D lattice Theoretical model : Here U: electric field; z: propagation distance; E 0 : applied DC field; D: lattice spacing; I 0 : lattice intensity; r 33 : electro-optic coefficient; k 0 = 2  0 ; k 1 = k 0 n e ;

7. Out-of phase dipole-solitons High intensity Moderate intensity Low intensity Lattice

8. In-phase dipole solitons High intensity Moderate intensity Low intensityLattice always unstable

9. Note: the above dipole solitons arise due to a balance of discrete diffraction nonlinearity, and lobe interactions They can not exist without the lattice.

10. Simulations of a pair of Gaussian beams Out-of phase In-phase Input Output Low NL High NL High NL No lattice

11. Quadrupole solitons Out-of-phase In-phase Can be stable Always unstable

12. Dipole solitons: experimental results In Phase Out of Phase Input Low NL High NL High NL No lattice Output

13. Anisotropic effect: out-of-phase case Input Low NL Low NL High NL No lattice with lattice with lattice Output These dipole solitons are robust against anisotropic effects

14. Anisotropic effect: in-phase case Input Output Low NL Intermediate NL High NL These dipole solitons are sensitive to anisotropic effects

15. Vector solitons in a 2D lattice If we make the two beams of the dipole incoherent, and launch into the same lattice site, then we can study vector lattice solitons

16. 2D vector lattice solitons: experiment Input Output Expt. results Num. results Low NL High NL High NL Coupled Decoupled Mutually Incoherent

17. 2D vector lattice solitons: theory Vector solitons can be derived from scalar ones by a polarization rotation:  (x, y) : scalar lattice soliton; : polarization Scalar 2D lattice solitons have been studied before: Yang and Musslimani, Opt. Lett. 2003 Efremidis, et al. PRL 2004

18. Dipole-like vector solitons in a 2D lattice If we make the two beams incoherent, and launch into different lattice sites, then we can study dipole- like vector lattice solitons Comb. input Low NL High NL 1 st comp. 2 nd comp. Expt. results Num. results

19. Conclusions a 1. We have demonstrated the formation of dipole, a quadrupole, vector, and dipole-like vector solitons in a a 2D photonic lattice for the first time. a 2. These solitons arise due to a balance of discrete a diffraction, nonlinearity, and lobe interactions. a 3. These solitons are stable in certain parameter regimes.

20. A scalar lattice soliton They are stable in a large parameter space

21. Dipole-like vector solitons in a 2D lattice If we make the two beams incoherent, and launch into different lattice sites, then we can study dipole- like vector lattice solitons Comb. input Low NL High NL 1 st comp. 2 nd comp. Expt. results Num. results