Low-loss fiber-to-chip couplers with ultrawide optical bandwidth

Providing efficient access from optical fibers to on-chip photonic systems is a key challenge for integrated optics. In general, current solutions allow either narrowband out-of-plane-coupling to a large number of devices or broadband edge-coupling to a limited number of devices. Here we present a hybrid approach using 3D direct laser writing, merging the advantages of both concepts and enabling broadband and low-loss coupling to waveguide devices from the top. In the telecom wavelength regime, we demonstrate a coupling loss of less than -1.8 dB between 1480 nm and 1620 nm. In the wavelength range between 730 nm and 1700 nm, we achieve coupling efficiency well above -8 dB which is sufficient for a range of broadband applications spanning more than an octave. The 3D couplers allow relaxed mechanical alignment with respect to optical fibers, with -1 dB alignment tolerance of about 5 μm in x- and y-directions and -1 dB alignment tolerance in the z-direction of 34 μm. Using automatized alignment, many such couplers can be connected to integrated photonic circuits for rapid prototyping and hybrid integration. © 2019 Author(s)

Silver-coated metallic and dielectric magnetic nanospheres: Localized surface plasmons and circular dichroism

A thorough study of localized surface plasmons and associated strong circular dichroism, which can occur in silver-coated metallic and dielectric magnetic nanospheres, is reported by means of both quasistatic and full electrodynamic calculations taking into account the actual (magneto) optical response of the constituent materials, including dispersion and losses. It is shown that such composite magnetoplasmonic nanoparticles offer a versatile platform for engineering hybrid plasmon modes that give rise to sharp absorption resonances and subject to large magneto-optic splitting, leading to giant magnetic circular dichroism signals, by properly choosing the different materials and tuning the geometrical parameters involved. © 2015 Elsevier B.V. All rights reserved

Enhanced Faraday rotation by crystals of core-shell magnetoplasmonic nanoparticles

Collective hybridized plasmon modes, which enable strong magnetooptical coupling and consequent enhanced Faraday effect in three-dimensional periodic assemblies of magnetic dielectric nanoparticles coated with a noble-metal shell, are studied by means of rigorous full electrodynamic calculations using an extension of the layer-multiple-scattering method, in conjunction with the effective-medium approximation. A thorough analysis of relevant photonic dispersion diagrams and transmission spectra provides a consistent explanation of the underlying physical mechanisms to a degree that goes beyond existing interpretation. It is shown that properly designed structures of such composite magnetoplasmonic nanoparticles offer a versatile platform for engineering increased and broadband Faraday rotation. © 2016 American Physical Society

Strong circular dichroism of core-shell magnetoplasmonic nanoparticles

Composite magnetoplasmonic nanoparticles with a core-shell morphology exhibit intriguing optical properties and offer impressive opportunities for tailoring in a controllable manner the light-matter interaction at subwavelength dimensions. These properties are usually analyzed in the framework of the quasi-static approximation, which, however, is often inadequate; thus, a full electrodynamic treatment is required. In this respect, we developed a rigorous method for an accurate description of electromagnetic scattering by a gyrotropic sphere coated with a nongyrotropic concentric spherical shell, based on the full multipole expansion of the wave field. The method was applied to specific examples of core-shell cobalt-silver spherical nanoparticles, where the occurrence of strong circular dichroism induced by magnetoplasmonic interaction, which largely exceeds that of homogeneous noble metal nanoparticles in an external magnetic field, was found. Our results were also explained by reference to the quasi-static approximation, which, though it reproduces the main features of the absorption spectra, strongly overestimates circular dichroism in the cases we studied. © 2015 Optical Society of America

Low-loss fiber-to-chip couplers with ultrawide optical bandwidth

Providing efficient access from optical fibers to on-chip photonic systems is a key challenge for integrated optics. In general, current solutions allow either narrowband out-of-plane-coupling to a large number of devices or broadband edge-coupling to a limited number of devices. Here we present a hybrid approach using 3D direct laser writing, merging the advantages of both concepts and enabling broadband and low-loss coupling to waveguide devices from the top. In the telecom wavelength regime, we demonstrate a coupling loss of less than −1.8 dB between 1480 nm and 1620 nm. In the wavelength range between 730 nm and 1700 nm, we achieve coupling efficiency well above −8 dB which is sufficient for a range of broadband applications spanning more than an octave. The 3D couplers allow relaxed mechanical alignment with respect to optical fibers, with −1 dB alignment tolerance of about 5 µm in x- and y-directions and −1 dB alignment tolerance in the z-direction of 34 µm. Using automatized alignment, many such couplers can be connected to integrated photonic circuits for rapid prototyping and hybrid integration