Topological lasing and self-induced transparency in two level systems

The use of virtually lossless topologically isolated edge states may lead to a novel class of thresholdless lasers operating without inversion. One needs however to understand if topological states may be coupled to external radiation and act as active cavities. We study a two-level topological insulator and show that self-induced transparency pulses can directly excite edge states. We simulate laser emission by a suitable designed topological cavity, and show that it can emit tunable radiation. For a configuration of sites following the off-diagonal Aubry-Andre-Harper model we solve the Maxwell-Bloch equations in the time domain and provide a first principle confirmation of topological lasers. Our results open the road to a new class of light emitters with topological protection for applications ranging from low-cost energetically-effective integrated lasers sources, also including silicon photonics, to strong coupling devices for studying ultrafast quantum processes with engineered vacuum

Two-Level Laser-like Emission by the Interaction of Self-Induced Transparency Solitons and Surface Anderson Localizations of Light

Self-induced transparency pulses propagating in a random medium embedded in a two-level system can transfer energy to localized Anderson states. This allows the onset of two-level laser-like action.Comment: 5 pages, 5 figures, revised versio

One- and two-photon scattering from generalized V-type atoms

The one- and two-photon scattering matrix S is obtained analytically for a one-dimensional waveguide and a point-like scatterer with N excited levels (generalized V -type atom). We argue that the two-photon scattering matrix contains sufficient information to distinguish between different level structures which are equivalent for single-photon scattering, such as a V -atom with N = 2 excited levels and two two-level systems. In particular, we show that the scattering with the V -type atom exhibits a destructive interference effect leading to two-photon Coupled-Resonator-Induced Transparency, where the nonlinear part of the two-photon scattering matrix vanishes when each incident photon fulfills a single-photon condition for transparency

Does Information Transparency Decrease Coordination Failure?

This study experimentally tests the effect of information transparency on the probability of coordination failure in global games with finite signals. Prior theory has shown that in global games with unique equilibrium, the effect of information transparency is ambiguous. We find that in global games where the signal space is finite, increased transparency has two effects. First, increasing the level of transparency usually destroys uniqueness and precipitates multiple equilibria, so that the effect of transparency on coordination depends crucially upon which equilibrium is actually attained. Second, the level of transparency determines which of these equilibria is risk dominant. We find that increased transparency facilitates coordination only if it switches the risk-dominant equilibrium from the secure equilibrium to the efficient equilibrium. When the converse is true, improved transparency can be dysfunctional because it increases the probability of coordination failure.