M. López-García

Studying light propagation in self-assembled hybrid photonic-plasmonic crystals by fourier microscopy.

Hybrid metallodielectric systems where dielectric components are combined with metals supporting surface plasmons are able to spatially redistribute the electromagnetic field intensity within its volume through hybrid photonic-plasmonic modes. While most of the work done recently in this kind of systems has been focused on the way such redistribution takes place and how light couples to or is emitted from such samples, the way light propagation takes place has not been studied in depth. Here we consider light propagation in hybrid systems fabricated by self-assembly methods measuring their equifrequency surfaces both in reflection and emission configurations. Comparing spectroscopic measurements with equifrequency surfaces provides a deeper insight into the way light propagates in these structures, showing the possibilities they may present for several applications.

Tunable magneto-photonic response of nickel nanostructures

In this letter, we present both experimental and numerical studies of the magneto-optical (MO) properties of nickel infiltrated opals. Ni can show interesting MO properties that can be controlled by nanostructuration through colloidal crystals templating. Nanostructuration allows the coupling of light to surface plasmon modes of Ni, and a clear dependence of the MO response as a function of the structural parameters of the template has been observed. This dependence can be used in future tunable devices such as switchers or MO modulators.

Magnetophotonic Response of Three- Dimensional Opals

Three-dimensional magnetophotonic crystals (3D-MPCs) are being postulated as appropriate platforms to tailor the magneto-optical spectral response of magnetic materials and to incorporate this functionality in a new generation of optical devices. By infiltrating self-assembled inverse opal structures with monodisperse nickel nanoparticles we have fabricated 3D-MPCs that show a sizable enhancement of the magneto-optical signal at frequencies around the stop-band edges of the photonic crystals. We have established a proper methodology to disentangle the intrinsic magneto-optical spectra from the nonmagnetic optical activity of the 3D-MPCs. The results of the optical and magneto-optical characterization are consistent with a homogeneous magnetic infiltration of the opal structure that gives rise to both a red-shift of the optical bandgap and a modification of the magneto-optical spectral response due to photonic bandgap effects. The results of our investigation demonstrate the potential of 3D-MPCs fabricated following the approach outlined here and offer opportunities to adapt the magneto-optical spectral response at optical frequencies by appropriate design of the opal structure or magnetic field strength.

Intrinsic losses in self-assembled hybrid metallodielectric systems

The light confinement properties of hybrid metallodielectric systems have been studied employing numerical simulations to obtain the optical response as well as the total field intensity associated with the different modes of the structure. The effect of intrinsic losses, absorption, and out-of-plane leakage on the quality factors (Q) of different modes is discussed, and the results obtained are interpreted in terms of the optical constants of the metallic substrate. Large Q values (up to 600) can be attained in this kind of samples, much larger than in their purely dielectric counterpart, pointing to the ability of these systems to efficiently confine electromagnetic radiation. V C 2011 American Institute of Physics. [doi:10.1063/1.3626856]

Ultrathin conformal coating for complex magneto-photonic structures

We report on an extremely fast and versatile synthetic approach, based on microwave assisted sol-gel chemistry, that allows a conformal nanometric coating of intricate three-dimensional structures. Using this methodology, we have achieved a conformal coverage of large areas of three-dimensional opals with a superparamagnetic manganese ferrite layer, yielding magneto-photonic crystals with excellent quality. The use of a ternary oxide for the ultrathin coating demonstrates the potential of this methodology to realize three-dimensional structures with complex materials that may find applications beyond photonics, such as energy, sensing or catalysis.

Light propagation in self-assembled hybrid metallodielectric structures

Self assembly is a well established approach to fabricate photonic structures able to manipulate light propagation and emission at the nanoscale [1]. Beyond its use as a means to fabricate photonic crystals recent reports have shown how self assembly techniques can be used to fabricate hybrid photonic-plasmonic crystals [2, 3] which allow strong modification of the spontaneous emission of internal sources [2]. Further, the sensitivity of their optical response to their environment has been proposed as a means to use this kind of systems of optical sensors [3], and means to control their optical properties by modifying the dielectric components have been demonstrated [4].

Enhancement and tailoring of hybrid self-assembled photonic-plasmonic crystals emission

Controlling emission by means of combined plasmonic and photonic modes has shown very promising results in the last years [1] with applications in several fields as laser devices or biosensing. Recently [2,3], it has been demonstrated that mixed structures formed by self-assembled photonic crystals based on monolayers of spheres and metallic substrates provide an easy-implementation fabrication method to obtain large emission enhancements as well as controllable angular emission patterns. It has also been demonstrated that large tunability can be easily achieved by means of after-grown polymeric spheres modifications [4]. Using a plasma etching technique, accurate control over the final diameter of the spheres and, as a consequence, over the optical response of the samples, can be achieved.