Fabricating high-index materials with designed three-dimensional (3D) micro optical elements is a challenging yet exciting area of research. Here, we develop an approach to 3D print high-index nanostructures of antimony trisulfide (Sb 2 S 3 ) using grayscale electron beam lithography (g-EBL). A key advantage of our approach is its simplicity compared to the conventional complex EBL-based metalens fabrication process. The refractive index of Sb 2 S 3 films is precisely determined using a computational genetic algorithm and the transfer matrix method. The Sb 2 S 3 structures show high fidelity and reproducibility, with the refractive index being tunable through thermal treatment. We demonstrate the fabrication and performance of 3D Fresnel Zone Plates (FZPs) and metalenses with the same design specification. Theoretical and experimental evaluation confirmed the diffraction-limited capability of as-fabricated 3D optical elements and indicates that the focusing efficiency of FZPs is higher compared to metalenses. This work advances the application of Sb 2 S 3 in micro- and nanoscale photonics, highlighting its potential for dynamic optical devices with precise control over output properties.

Recent advancements in photonics have intensified the performance requirements for optical systems and present significant challenges for optical coating technologies. Conventional interference coating systems often prove to be insufficient, especially in applications requiring large angles of light incidence or a wide wavelength range. Nanostructures, which consist of an air material mixture, offer promising alternatives. In this work, silica nanostructures are manufactured by the AR-plas2 method, in which first an organic layer is evaporated onto a substrate. This organic layer forms self-organizing nanostructures by a plasma etching step, which are subsequently coated with silica. Finally, the organic residues are removed by additional plasma etching and heat treatment steps, which results in hollow silica structures. The work examines the optical and functional properties of these structures designed for 355 nm to demonstrate their use as anti-reflective coatings for advanced optical systems.

The paper discusses requirements and solutions for antireflection coatings applicable for a fused silica cell which is attended to manipulate Rydberg atoms as qubits. Multiple laser beams at various wavelengths and light incidence angles pass the different window areas of the cell. AR-coatings were designed and deposited on the window areas to receive an optimal solution for each of the lasers. Some of the coatings optimized for the internal surfaces of the cell contain nanostructured layers as an option to improve the polarization properties at higher light incidence angles. Cleaning, handling and outgassing of these layers was investigated in particular.

The rise of micro/nanooptics and lab-on-chip devices demands the fabrication of three-dimensional structures with decent resolution. Here, we demonstrate the combination of grayscale electron beam lithography and direct forming methodology to fabricate antimony sulfide structures with free form for the first time. The refractive index of the electron beam patterned structure was calculated based on an optimization algorithm that is combined with genetic algorithm and transfer matrix method. By adopting electron irradiation with variable doses, 4-level Fresnel Zone Plates and metalens were produced and characterized. This method can be used for the fabrication of three-dimensional diffractive optical elements and metasurfaces in a single step manner.

To increase the performance of optical systems, a good antireflective coating is required to ensure low reflectance and high transmittance of optical surfaces. Further problems, such as fogging that causes light scattering, negatively affect the image quality. This implies that other functional properties are also required. Presented here is a highly promising combination of an antireflective double nanostructure on top of an antifog coating with long-term stable properties, generated in a commercial plasma-ion-assisted coating chamber. It is demonstrated that the nanostructures do not affect the antifog properties and can be successfully used for many applications.

A major problem for optical systems is the polarization splitting occurring at any interface in the event of oblique light. Low-index nanostructured silica layers were produced by overcoating an initial organic structure with silica and subsequent removal of the organic constituents. The nanostructured layers can be tailored to achieve defined low effective refractive indices down to 1.05. They can also be stacked together with homogeneous layers to produce broadband antireflective coatings with very low polarization splitting. Especially thin interlayers that separate the low-index structured layers turned out to be useful to optimize the polarization properties.

With commercial plasma-ion-assisted deposition technology, we generated a very convincing combination of an antireflective double-nanostructure on top of an antifog coating with long-term stable properties. The nanostructure does not affect the antifog properties and can be successfully used for LiDAR applications.

Low-index nanostructured silica layers can be produced by overcoating an initial organic structure with silica and subsequent removal of the organic constituents. The silica layers can be tailored to achieve defined effective refractive indices and thicknesses. Polarization-neutral antireflective coatings for light incidence angles up to 70° were designed by combining two nanostructured layers with a few homogeneous oxide and fluoride layers.

High-transparent polymers exhibiting a refractive index beyond 1.6 enhance the available range of optical plastics. The aim of this study is to evaluate optical polyesters (OKP-1 and OKP-4) and special new polycarbonates (PCs) (EP-6000 and EP-8000) in comparison with the widely used poly-bisphenol-A-based PC. The work is focused on optical properties as well as other properties that are important for the deposition of optical coatings. Plasma ion-assisted deposition is used for the deposition of an abrasion resistant antireflective coating (AR-hard).

Anti-reflective (AR) coatings are indispensable for an excellent imaging of optical systems. Common AR coating systems consist of layer stacks of alternating low and high refractive index materials with the residual reflection depending mainly on the low refractive index (LRI) of the last layer relative to air. However, conventional LRI materials are limited to SiO2 (n = 1,46 at 532 nm) and MgF2 (n = 1,38 at 532 nm), where MgF2 is not environmentally stable. Nanostructures with an adjustable effective LRI in the range of 1.07 to 1.25 are an attractive alternative to these materials. Integrated as the last layer in the stack system, these structures significantly improve the optical performance compared to a conventional interference coating system, as a broadband AR coating can be realized, which is less sensitive to high angles of light incidence. Nanostructures can be produced using various methods - e.g. wet chemical or lithographic. However, these methods are expensive and time-consuming, as often more than one manufacturing step is necessary. At the Fraunhofer Institute IOF in Jena, self-assembling AR nanostructures have already been successfully fabricated for several years using a conventional plasma-ion-assisted-deposition (PIAD) technology. Thereby organic material is deposited on the substrate via thermal evaporation and subsequently self-assembling nanostructures are formed by an ion plasma source. Melamine and Uracil are already being used successfully as organic material. The advantage of this method is the generation of nanostructures in one process which is cost- and time-effective. In this talk, we want to introduce Xanthine, another organic material that is also highly promising for the generation of nanostructures exhibiting an LRI. We will demonstrate the formation of these nanostructures during plasma etching and investigate their optical performance for the use as an AR coating.

Surface contaminations can critically affect the performance of optical surfaces, in particular with respect to light scattering, optical losses, and laser stability. Thus, avoiding contaminations and reducing contamination-induced effects is of particular interest in the manufacturing of optical systems. By combining a specific thin film design with a tailored structural design, contamination-resistant coatings with a high optical quality can be realized. Most important is the balance of self-cleaningand light scattering-relevant surface roughness components.