Conference Agenda

Nanostructures can be used to tailor light-matter interaction in many ways. Optical metasurfaces composed of two-dimensional configurations of sub-wavelength sized metallic or dielectric nanostructures have a large range of potential applications, e.g., in imaging or as sensors. Their combination with optoelectronic devices can enable and enhance device functionality as well as facilitate material integration. We report on the transfer of prototype realizations of on-chip refractive index sensors and wavelength-selective photodetectors from university cleanrooms to a 200 mm Si platform. Our results not only highlight challenges and opportunities in implementing metasurfaces as functional device layers, they also showcase the advantages of using high precision Si technology for the fabrication of nanophotonic structures.

Optical interferometry offers exceptional measurement precision, while integrated optics enables compact, robust photonic platforms. Here we combine both by developing an integrated photonic sensor based on a tunable Mach–Zehnder interferometer fabricated on a glass chip via direct laser writing. We investigate optical losses across each section of the device and carry out preliminary classical-light characterization. While a full performance assessment is ongoing, initial results are promising and support the viability of laser-written glass waveguides for high-sensitivity chip-scale sensing. This work lays the groundwork for future quantum-enhanced sensing experiments exploiting the same integrated architecture.

We investigate laser-induced modifications in a titanium-overcoated SiO₂ dielectric layer using second harmonic generation (SHG) as a sensitive optical probe. Employing femtosecond laser pulses at 1028 nm, we perform spatially resolved measurements across the interface between bare and Ti/Si₃N₄-overcoated regions of the sample. We find that the metal overcoating significantly reduces the safe operating fluence, with irreversible changes occurring above 0.3 J/cm², attributed to localized heating by absorption in the Ti layer and Si substrate. Our results highlight SHG as a powerful diagnostic tool for assessing laser-damage thresholds in metal-overcoated dielectric systems.

Chalcogenide glasses such as As₂Se₃ are attractive optical materials for infrared photonics, optical fiber technologies, and light-responsive functional devices. In these materials, light exposure may induce metastable structural changes that are closely related to defect formation and relaxation processes, which are important for long-term material stability and performance. In this work, we investigate the effect of laser irradiation on As₂Se₃ optical fibers by fast differential scanning calorimetry. Fibers exposed to different irradiation times and power densities were measured immediately after treatment in order to probe light-induced metastable states. The calorimetric response shows a systematic evolution of the sub-Tg relaxation, with a progressive reduction in the β-related contribution as irradiation time increases at both low and high power densities. This behavior is consistent with irradiation-induced modifications of defect-related local configurations involved in structural relaxation.

Potassium titanyl phosphate (KTP) is a widely used nonlinear optical crystal due to its large second-order susceptibility and broad transparency range. However, second-harmonic generation (SHG) at Ti:Sapphire laser wavelengths (~800 nm) cannot be achieved through birefringent phase matching, typically requiring quasi-phase-matching techniques. Here, we demonstrate that femtosecond-laser-induced microstructures in KTP enable spatially localized enhancement of SHG under phase-mismatched conditions. Subsurface damage tracks were inscribed using 60 fs Ti:Sapphire laser pulses at 800 nm. The nonlinear optical response of the inscribed microstructures was investigated through two complementary approaches: microscale analysis using second-harmonic and Raman microscopy, revealing localized enhancement and structural modifications, and large-beam excitation under loose focusing conditions, showing periodic SH modulation consistent with the microstructure pattern. These results demonstrate a local enhancement of the nonlinear optical response in KTP, opening new possibilities for the design of integrated nonlinear photonic devices.