As an example of integrated hybrid photonic device, azobenzene-functionalized silica toroidal resonators have been demonstrated to show a stable, reversible spectral tunability up to about 4 nm at telecom wavelengths, upon illumination with external laser sources in the visible. azobenzenes and dithienylethene ) represent a valuable option in hybrid organic–inorganic architectures, mainly because of the large variety of different light-responsive mechanisms available and the moderate power required to the external radiation to trigger the photoswitching functionalities. Alternatively, polymeric compounds containing light-active units (e.g. With this respect, intensive research efforts are presently directed towards new optical materials, such as transparent conductive oxides and semiconductors, with tailored linear and non-linear properties enabling an optical modulation based on sufficiently strong, yet reversible, refractive index changes. based on thermo-optical or photo-acoustic effects), since they allow reaching a considerable spatial selectivity and a minimal cross-talk with adjacent circuit parts. Modulation strategies involving all-optical control are particularly advantageous in integrated photonic chips as compared to other approaches (e.g. In many active devices, changes in the refractive index of constituent materials can be obtained after providing an external luminous trigger, often in the form of focused laser beams.
Tunable photonics deals with micro and nanostructures able to modify some of their optical functions and properties upon external cues, which are typically fed as control means in active devices or measurand in sensing architectures. The proposed approach based on tailored birefringence opens up new pathways to finely control the optical coupling of localized surface modes to/from free-space radiation, particularly in hybrid organic–inorganic devices. The polymeric structure is constituted by a novel blend of an azopolymer and a thermally-sensitive resist, which allows a precise patterning via thermal scanning probe lithography, while providing a significant structural integrity against photo-fluidization or mass-flow effects commonly occurring in irradiated azopolymers. Overall, reversible blue- and red-shifts of the resonant BSWs are observed within a spectral range of about 2 nm, with a moderate laser power illumination. We demonstrate that a dynamic control on the resonant mode energies can be easily operated by modulating the orientation of the optically-induced birefringence on the surface, via a polarized external laser beam.
Thanks to the cavity morphology, two surface resonant modes with substantially orthogonal polarizations can be coupled within the cavity from free-space illumination. Here, we design and fabricate an anisotropic two-dimensional bull’s eye cavity inscribed within an optically-active polymeric film spun on a one-dimensional photonic crystal sustaining Bloch surface waves (BSW). In this framework, optically-induced anisotropy has been proposed as powerful mean enabling tuning functionalities in several planar architectures. Fostered by the recent advancements in photonic technologies, the need for all-optical dynamic control on complex photonic elements is emerging as more and more relevant, especially in integrated photonics and metasurface-based flat-optics.
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