m-bonacci metamaterial multilayers: location of the zero-average index bandgap edges

Non-Bragg-gap solitons in one-dimensional Kerr-metamaterial Fibonacci heterostructures

A detailed study of non-Bragg-gap solitons in one-dimensional Kerr-metamaterial quasiperiodic Fibonacci heterostructures is performed. The transmission coefficient is numerically obtained by combining the transfer-matrix formalism in the metamaterial layers with a numerical solution of the nonlinear differential equation in the Kerr slabs, and by considering the loss effects in the metamaterial slabs. A switching from states of no transparency in the linear regime to high-transparency states in the nonlinear regime is observed for both zero-order and plasmon-polariton gaps. The spatial localization of the non-Bragg-gap solitons is also examined, and the symmetry properties of the soliton waves are briefly discussed.

Measuring the roughness of buried interfaces by sputter depth profiling

We report results of high-resolution sputter depth profiling of an alternating MgO/ZnO nanolayer stack grown by atomic layer deposition (ALD) of ≈5.5 nm per layer. We used an improved dual beam time-of-flight secondary ion mass spectrometer to measure (24)Mg(+) and (64)Zn(+) intensities as a function of sample depth. Analysis of depth profiles by the mixing-roughness-information model yields a 1.5 nm nanolayer interfacial roughness within the MgO/ZnO multilayer. This finding was cross-validated using specular x-ray reflectivity. Such an analysis further suggested that the 1.5 nm roughness corresponds to native/jig-sawed interfacial roughness rather than interfacial interdiffusion during the ALD growth.

Exploiting aperiodic designs in nanophotonic devices

In this work we consider the role of aperiodic order-order without periodicity-in the design of different optical devices in one, two and three dimensions. To this end, we will first study devices based on aperiodic multilayered structures. In many instances the recourse to Fibonacci, Thue-Morse or fractal arrangements of layers results in improved optical properties compared with their periodic counterparts. On this basis, the possibility of constructing optical devices based on a modular design of the multilayered structure, where periodic and quasiperiodic subunits are properly mixed, is analyzed, illustrating how this additional degree of freedom enhances the optical performance in some specific applications. This line of thought can be naturally extended to aperiodic arrangements of optical elements, such as nanospheres or dielectric rods in the plane, as well as to three-dimensional photonic quasicrystals based on polymer materials. In this way, plentiful possibilities for new tailored materials naturally appear, generally following suitable optimization algorithms. Then, we present a detailed discussion on the physical properties supporting the preferential use of aperiodic devices in a number of optical applications, opening new avenues for technological innovation. Finally we suggest some related emerging topics that deserve some attention in the years to come.