Université de Fribourg

Band gap formation and Anderson localization in disordered photonic materials with structural correlations

Froufe-Pérez, Luis S. ; Engel, Michael ; Sáenz, Juan José ; Scheffold, Frank

In: Proceedings of the National Academy of Sciences, 2017, vol. 114, no. 36, p. 9570–9574

Disordered dielectric materials with structural correlations show unconventional optical behavior: They can be transparent to long-wavelength radiation, while at the same time have isotropic band gaps in another frequency range. This phenomenon raises fundamental questions concerning photon transport through disordered media. While optical transparency in these materials is robust against...

Université de Fribourg

Controlling dispersion forces between small particles with artificially created random light fields

Brügger, Georges ; Froufe-Pérez, Luis S. ; Scheffold, Frank ; Sáenz, Juan José

In: Nature Communications, 2015, vol. 6, p. 7460

Appropriate combinations of laser beams can be used to trap and manipulate small particles with optical tweezers as well as to induce significant optical binding forces between particles. These interaction forces are usually strongly anisotropic depending on the interference landscape of the external fields. This is in contrast with the familiar isotropic, translationally invariant, van der Waals...

Université de Fribourg

Fluctuations of the electromagnetic local density of states as a probe for structural phase switching

Sousa, N. de ; Sáenz, Juan José ; Scheffold, Frank ; García-Martín, A. ; Froufe-Pérez, Luis S.

In: Physical Review A, 2016, vol. 94, no. 4, p. 043832

We study the statistics of the fluorescence decay rates for single quantum emitters embedded in a scattering medium undergoing a phase transition. Under certain circumstances, the structural properties of the scattering medium explore a regime in which the system dynamically switches between two different phases. While in that regime the light-scattering properties of both phases are hardly...

Université de Fribourg

Magneto-Optical Activity in High Index Dielectric Nanoantennas

Sousa, N. de ; Froufe-Pérez, Luis S. ; Sáenz, Juan José ; García-Martín, A.

In: Scientific Reports, 2016, vol. 6, p. 30803

The magneto-optical activity, namely the polarization conversion capabilities of high- index, non-absorbing, core-shell dielectric nanospheres is theoretically analyzed. We show that, in analogy with their plasmonic counterparts, the polarization conversion in resonant dielectric particles is linked to the amount of electromagnetic field probing the magneto-optical material in the system....

Université de Fribourg

Negative scattering asymmetry parameter for dipolar particles: Unusual reduction of the transport mean free path and radiation pressure

Gómez-Medina, R. ; Froufe-Pérez, Luis S. ; Yépez, M. ; Scheffold, Frank ; Nieto-Vesperinas, M. ; Sáenz, Juan José

In: Physical Review A - Atomic, molecular and optical physics, 2012, vol. 85, no. 3, p. 035802

Lossless dielectric nanospheres (made of nonmagnetic materials) with relatively low refraction index may present strong electric and magnetic dipolar resonances. We establish a relationship between the optical force from a plane wave on small electric and magnetic dipolar particles, the transport cross section, and the scattering asymmetry parameter g. In this way we predict negative g (that...

Université de Fribourg

Self-diffusion and structural properties of confined fluids in dynamic coexistence

Sousa de, N. ; Sáenz, Juan José ; Scheffold, Frank ; García-Martín, A. ; Froufe-Pérez, Luis S.

In: Journal of Physics: Condensed Matter, 2016, vol. 28, no. 13, p. 135101

Self-diffusion and radial distribution functions are studied in a strongly confined Lennard-Jones fluid. Surprisingly, in the solid–liquid phase transition region, where the system exhibits dynamic coexistence, the self-diffusion constants are shown to present up to three-fold variations from solid to liquid phases at fixed temperature, while the radial distribution function corresponding...

Université de Fribourg

Strong magnetic response of submicron Silicon particles in the infrared

García-Etxarri, A. ; Gómez-Medina, R. ; Froufe-Pérez, Luis S. ; López, C. ; Chantada, Laura ; Scheffold, Frank ; Aizpurua, J. ; Nieto-Vesperinas, M. ; Sáenz, Juan José

In: Optic Express, 2011, vol. 19, no. 6, p. 4815

High-permittivity dielectric particles with resonant magnetic properties are being explored as constitutive elements of new metamaterials and devices. Magnetic properties of low-loss dielectric nanoparticles in the visible or infrared are not expected due to intrinsic low refractive index of optical media in these regimes. Here we analyze the dipolar electric and magnetic response of lossless...

Université de Fribourg

Transport of light in amorphous photonic materials

Reufer, Mathias ; Rojas-Ochoa, Luis Fernando ; Eiden, Stefanie ; Sáenz, Juan José ; Scheffold, Frank

In: Applied Physics Letters, 2007, vol. 91, no. 17, p. 171904

Amorphous photonic materials based on dense assemblies of high refractive index spherical particles are presented. Light transmission through these photonic glasses shows a nontrivial wavelength dependence. The transmission spectra can be quantitatively reproduced by modeling the optical properties starting from their building blocks. Our results emphasize the relevance of including short range...

Université de Fribourg

Unequivocal signatures of the crossover to Anderson localization in realistic models of disordered quasi-one-dimensional materials

Lopez-Bezanilla, Alejandro ; Froufe-Pérez, Luis S. ; Roche, Stephan ; Sáenz, Juan José

In: Physical Review B, 2018, vol. 98, no. 23, p. 235423

The only unequivocal known criterion for single-parameter scaling Anderson localization relies on the knowledge of the full conductance statistics. To date, theoretical studies have been restricted to model systems with symmetric scatterers, hence lacking universality. We present an in-depth statistical study of conductance distributions P(g), in disordered ‘micrometer-long’ carbon...