A novel technique is developed to improve the resolution of two‐photon direct laser writing lithography. Thanks to the high collimation enabled by extraordinary εNZ (near‐zero) metamaterial features, ultrathin dielectric hyper‐resolute nanostructures are within reach. With respect to the standard direct laser writing approach, a size reduction of 89% and 50%, in height and width respectively, is achieved with the height of the structures adjustable between 5 and 50 nm. The retrieved 2D fabrication parameters are exploited for realizing extremely thin all‐dielectric metalenses tailored through deep machine learning codes. The hyper‐resolution achieved in the writing process enables the fabrication of a highly detailed dielectric 3D bas‐relief (with full height of 500 nm) of Da Vinci's “Lady with an Ermine”. The proof‐of‐concept results show intriguing cues for the current and trendsetting research scenario in anti‐counterfeiting applications and ultracompact photonics, paving the way for the realization of all‐dielectric and apochromatic ultrathin imaging systems.
We present an experimental characterization and a comprehensive theoretical modeling of macroscopic plasmonic heat production that takes place in a single layer of small gold nanoparticles (GNPs), randomly distributed on a glass substrate, covered with different host media and acted on by a resonant radiation. We have performed a detailed experimental study of the temperature variations of three different systems, obtained by varying the density of nanoparticles. Due to the macroscopic dimension of the spot size, the used laser irradiates a huge number of nanoparticles, inducing a broad thermo-plasmonic effect that modifies the thermal conductivity of the entire system; starting from the state of art, we have implemented a simple model that enables to evaluate the resulting new thermal conductivity. We have also extended our theoretical approach to the macroscale, including an analysis of the effects predicted for different NP densities and laser spot size values, as well as for different values of the laser intensity, which can be as low as 0.05 W cm −2 . Theoretically predicted temperature variations are in excellent agreement with experimental results.
A major challenge towards nanophotonics is the integration of nanoemitters on optical chips. Combining the optical properties of nanoemitters with the benefits of integration and scalability of integrated optics is still a major issue to overcome. In this work, we demonstrate the integration of nanoemitters positioned in a controlled manner onto a substrate and onto an optical ion-exchanged glass waveguide via direct laser writing based on two-photon polymerization. Our nanoemitters are colloidal CdSe/ZnS quantum dots (QDs) embedded in polymeric nanostructures. By varying the laser parameters during the patterning process, we make size-controlled QD-polymer nanostructures that were systematically characterized using optical and structural methods. Structures as small as 17 nm in height were fabricated. The well-controlled QD-polymer nanostructure systems were then successfully integrated onto a new photonic platform for nanophotonics made of an ion-exchanged waveguide. We show that our QDs maintain their light emitting quality after integration as verified by photoluminescence (PL) measurements. Ultimately, QD emission coupled to our waveguides is detected through a home-built fiber-edge coupling PL measurement setup. Our results show the potential for future integration of nanoemitters onto complex photonic chips.
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