Lattice topology and spontaneous parametric down-conversion in quadratic nonlinear waveguide arrays

We analyze spontaneous parametric down-conversion in various experimentally feasible 1D quadratic nonlinear waveguide arrays, with emphasis on the relationship between the lattice's topological invariants and the biphoton correlations. Nontrivial topology results in a nontrivial "winding" of the array's Bloch waves, which introduces additional selection rules for the generation of biphotons. These selection rules are in addition to, and independent of existing control using the pump beam's spatial profile and phase matching conditions. In finite lattices, nontrivial topology produces single photon edge modes, resulting in "hybrid" biphoton edge modes, with one photon localized at the edge and the other propagating into the bulk. When the single photon band gap is sufficiently large, these hybrid biphoton modes reside in a band gap of the bulk biphoton Bloch wave spectrum. Numerical simulations support our analytical results.Comment: 11 pages, 12 figure

Infrared spectra of some sulfides and their analogs of binary composition in the long-wave region

The far infrared spectra (500-60/cm) of some simple sulfides and their analogs were studied. In all, 22 minerals with different structure types were investigated, out of which 14 are sulfides (galena, alabandite, pyrrhotite, sphalerite, wurtzite, cinnabar, realgar, orpiment, getchelite antimonite, molybdenite, pyrite, marcasite and heazlewoodite) 6 arsenides (niccolite, domeykite, arsenopyrite, lollingite, rammelsbergite and skutterudite), one telluride (tetradymite) and native arsenic. The main bands of infrared absorption spectra of the minerals are compared with the relative strength of the interatomic bonds and their interpretation is given

Temporal dynamics of all-optical switching in quadratic nonlinear directional couplers

We study the temporal dynamics of all-optical switching in nonlinear directional couplers in periodically poled lithium niobate. The characteristic features of such switching, including asymmetric pulse break-up and back-switching were measured in full agreement with the theoretical predictions. Based on the time-resolved measurement of intensity-dependent switching, finally the theoretically long-known continuous-wave switching curve has experimentally been confirmed.We acknowledge the support by the Australian Research Council Centre of Excellence program (project CE110001018), the Australian Academy of Science, and the International Bureau of the Federal Ministry of Education and Research (BMBF), Germany (Australia-Germany Researcher Mobility Call 2010-2011)