Elisa Nicoletti

Observation of multiple higher-order stopgaps from three-dimensional chalcogenide glass photonic crystals

For the first time to our knowledge the observation of near-IR multiple higher-order stopgaps in three-dimensional photonic crystals (PhCs) fabricated using the direct-laser-writing method in thick chalcogenide glass films is reported. The fabrication and etching conditions necessary to realize well-defined structures are presented. The fabricated PhCs exhibit higher-order stopgaps, which are only evident in high-quality structures. The higher-order stopgaps observed permit these high-refractive-index and high-nonlinear PhCs to be used directly as functional photonic devices operating at telecommunication wavelengths without further miniaturizing structural dimensions.

Generation of λ/12 Nanowires in Chalcogenide Glasses

Nanowires have been widely studied and have gained a lot of interest in the past decade. Because of their high refractive index and high nonlinearity, chalcogenide glasses (ChGs) are a good candidate for the fabrication of photonic nanowires as such nanowaveguides provide the maximal confinement of light, enabling large enhancement of nonlinear interactions and group-velocity dispersion engineering. Here we report on the generation of λ/12 (∼68 nm) nanowires based on the theoretical and experimental study of the influence of the laser repetition rate on the direct laser fabrication in ChGs (λ = 800 nm). Through a numerical model of cumulative heating, the optimum conditions for high-resolution fabrication in As(2)S(3) are found. Nanowires with dimensions down to ∼λ/12 are for the first time successfully fabricated in ChGs. We show that the generated nanowires can be stacked to form a three-dimensional woodpile photonic crystal with a pronounced stop gap.

Planar defects in three-dimensional chalcogenide glass photonic crystals

Here we report on the direct laser writing fabrication of Fabry-Perot-type planar microcavities in a three-dimensional (3D) photonic crystal (PhC) embedded within a high-refractive nonlinear chalcogenide glass (ChG) film. The fabricated planar microcavities in a nonlinear ChG 3D PhC facilitate the observation of resonant modes inside the stop gap. The experimental results show that the length of the planar cavity can be well controlled by the fabrication power and thus be used to tune the defect modes. The tunability of the observed defect modes is confirmed by the theoretical prediction.

Engineering the refractive index of three- dimensional photonic crystals through multilayer deposition of CdS films

Woodpile photonic crystals are amongst the preferred candidates for the next generation of photonics components. However, the photocurable resists used to produce them still lack the optical properties (high-n, non-linearity) suitable for photonics applications. A chemical bath deposition protocol has been adapted to deposit high-n/non-linear chalcogenide CdS on the surface of Ormocer woodpiles. The deposition parameters have been adjusted to obtain heterogeneous growth of CdS layers on the Ormocer surface. The layers shift the photonic band-gap and increase its amplitude by more than 15%. Software simulation confirmed that the woodpile effective refractive index underwent an excess of 30% increase.

High resolution fabrication in chalcogenide glasses

Here we report on the theoretical and experimental study of the influence of the laser repetition rate on the direct laser fabrication in chalcogenide glasses (ChGs). Through a numerical model of cumulative heating the optimum conditions for high resolution fabrication in AS2S3 were found. Nanowires with dimensions down to ≈λ/12 have been for the first time successfully fabricated in ChGs.