Research Results

Microfabrication method development

FABulous investigates complimentary approaches for high resolution (<200nm), high speed (>2E7 voxels/s), multi-photon printing of 3D metasurfaces. The aim is to identify the optimum method for manufacturing metasurfaces with different applications.

Massively parallelised lithographic printing: This approach is based on massively parallelised lithographic printing which has been shown to enable writing of up to millions of voxels per exposure while reducing 3D proximity effects. Novel methods for multi-photon writing, based on the knowledge of existing parallel write technique using Spatial Light Modulators (SLM) and Diffractive Optical Elements (DOE), have been developed by IMTA with the aim of identifying the best engineering compromise for the numerous process parameters and constraints (write wavelength, available lasers, projection lens resolution and write field, resist sensitivity etc).

Robust testing found that the DOE approach is better suited to high-speed fabrication over large areas due to the energetic efficiency of the DOE, as this means that the system can withstand very high laser power, which enables large numbers of intense write spots to be used simultaneously. Using this approach, we have demonstrated fabrication of structures which are <200nm, at our target plot rate of 2E7 voxels/s, on flat surfaces. However, optimisation of the process to explore whether it is possible to achieve equivalent or even better performance on more complex surfaces is ongoing.

DOEmodulation2 (2)
DOEmodulation2 (2)
Double-T-Structure-11102023-3
Double-T-Structure-11102023-3
Caro-Slanted-25102023-2 (1)
Caro-Slanted-25102023-2 (1)

 

Holographic layer by layer 3D printing: This approach is based on the use of spatial temporal pulse shaping to reduce, or completely remove, undesired out-of-plane polymerisation. A custom set up for high speed, high resolution fabrication of metasurface structures has been established at FORTH and work is underway to evaluate the plot rate that can be achieved with this approach.

FAB 3d structures
FAB 3d structures 2
FAB 3d structures 3

Integrated metasurface design and process modelling

Industrial scale manufacturing of products with integrated metasurfaces requires the development of methods and tools that connect system level design with metasurface design so that the resulting product can fully exploit the unique functions that the metasurface can provide. To this end FABulous has developed approaches for multi-scale simulation of metasurface enabled products from nano-scale to meter-scale.

Researchers at POS, THALES and FORTH have been working on a multi-scale simulation approach that combines full-wave solutions, wave optics, and ray tracing to bridge the nanoscale-to macroscale gap. Two interfacing methods, grounded in physical theory, were specifically developed for FABulous and have been applied in the design of demonstrator products with seamless integration across these scales. The team have now validated their methods through comparisons across software platforms and successfully demonstrated that end-to-end design of meta-surfaces for innovative applications including automotive camera lenses, light pipes, and solar micro-optic arrays is possible, marking a major step forward in scalable optical system design.

In addition, FRAUNHOFER has been exploring the use of rapid simulation to co-optimize the metasurfaces with the optical elements of the target products, ensuring  that the final products can take maximum benefit from the integrated metasurface. They have developed physical models for optical proximity correction (OPC) to improve the fidelity and resolution of the FABulous direct write process and enable faster printing of 3D surface components. With a particular focus on understanding pattern formation during the parallelized fabrication process when employing a spatial light modulator (SLM) and an ultrasensitive triplet-triplet annihilation (TTA) resist. Phenomenological modelling of the FABulous process has demonstrated that pre-compensation of proximity effects improves pattern fidelity and enables faster writing speeds. An example comparison of the results of our simulation work with experimental results is shown below.

Enabling optical metasurface manufacturing at industrial scale

FABulous is more than just a research project, it also seeks to convert the new knowledge and techniques developed within the project into practical tools and processes for industrial scale manufacturing with submicrometric resolution.

Our technology partners, HIMT and AIMEN are currently hard at work applying the learning from our work to develop the robust microfabrication methods and process control techniques, to produce and adapt the technology platforms required for manufacturing of metasurfaces on real world optical products at industrially relevant throughputs. This includes the development of systems for the handling, measurement, coating and printing on non-planar substrates and the development the control systems necessary to ensure the technical and quality requirements of end use applications are achieved.

In the final year of the project the resulting solutions will be used to demonstrate the manufacturing of metasurfaces on three distinct optical products (sensors, lights, solar panels), with progressively challenging requirements in terms of size (1cm2 to >30cm2) and substrate (curved, cylindrical, free form).

FAB Use Cases - Sensor
FAB Use Cases - Sensor
FAB Use Cases - Light
FAB Use Cases - Light
FAB Use Cases - solar
FAB Use Cases - solar

 

Life Cycle Assessment

Metasurfaces have the potential to reduce the environmental footprint of commercial products through enhanced efficiency, material savings, increased durability, and better recycling. However, the realization of these benefits requires that the lifecycle impacts of products with integrated metasurfaces are thoroughly assessed and optimized. FABulous is working to understand the extent to which manufacturing of products with integrated metasurfaces reduces their environmental footprint. To do so our partner IRES is conducting lifecycle assessments (LCA) for each of the FABulous use cases. LCA is a systematic approach for evaluating the environmental impacts associated with all stages of a product’s life, from raw material extraction through manufacturing, use, and disposal or recycling. Throughout the project the environmental impact of the FABulous production process will be monitored and measured to assess where materials savings can be made and whether production is more efficient using the FABulous techniques.