Ermakov-Lewis symmetry in photonic lattices

We present a class of waveguide arrays that is the classical analog of a quantum harmonic oscillator where the mass and frequency depend on the propagation distance. In these photonic lattices refractive indices and second neighbor couplings define the mass and frequency of the analog quantum oscillator, while first neighbor couplings are a free parameter to adjust the model. The quantum model conserves the Ermakov-Lewis invariant, thus the photonic crystal also posses this symmetry.Comment: 8 pages, 3 figure

Efficient optical energy harvesting in self-accelerating beams

We report the experimental observation of energetically confined self-accelerating optical beams propagating along various convex trajectories. We show that, under an appropriate transverse compression of their spatial spectra, these self-accelerating beams can exhibit a dramatic enhancement of their peak intensity and a significant decrease of their transverse expansion, yet retaining both the expected acceleration profile and the intrinsic self-healing properties. We found our experimental results to be in excellent agreement with the numerical simulations. We expect further applications in such contexts where power budget and optimal spatial confinement can be important limiting factors

N-gram and local context analysis for Persian text retrieval

The Persian language is one of the languages in Middle- East, so there are significant amount of Persian documents available on the Web. But there are relatively few studies on retrieval of Persian documents in the literature. In this experimental study, we assessed term and N-gram based vector space model and a query expansion method, namely, Local Context Analysis using different weighting schemes on a realistic corpus containing 160000+ news articles. Then we compared our results with previous works reported on Persian language. Our experimental results show that among the assessed methods, 4-gram based vector space model with Lnu.ltu weighting scheme has acceptable performance and Local Context Analysis has the best performance for Persian text retrieval so far

Controllable Red And Blue Shifting Of Ingaasp Quantum Well Bandgap Energy For Photonic Device Integration

Wedemonstrate bandgap tuning of InGaAsP multiple quantum well structures by utilizing an impurity-free vacancy diffusion technique. Substantial modification of the bandgap energy toward the red and blue parts of the spectrum has been observed using SiO2/SiOyNx/SiNx capping layers and by controlling the associated oxygen and nitrogen content. The resulting degree of tuning, up to 120 nm red shift and 140 nmblue shift of the band-to-band wavelength emission, has been studied using room-temperature photoluminescence, in agreement with the emission spectra obtained from semiconductor optical amplifier waveguide strips

Ermakov-Lewis Symmetry In Photonic Lattices

We present a class of waveguide arrays that is the classical analog of a quantum harmonic oscillator, where the mass and frequency depend on the propagation distance. In these photonic lattices, refractive indices and secondneighbor couplings define the mass and frequency of the analog quantum oscillator, while first-neighbor couplings are a free parameter to adjust the model. The quantum model conserves the Ermakov-Lewis invariant, thus the photonic crystal also possesses this symmetry. © 2014 Optical Society of America