Periodic Reporting for period 1 - 3D-Optics (Diffractive Optical Element Fabrication based on 3D Printing)
Reporting period: 2023-01-01 to 2025-06-30
The project addresses a critical bottleneck in modern optics – fabrication of Diffractive Optical Elements (DOEs). Diffractive optical elements offer exceptional flexibility in wavefront shaping, enabling the implementation of complex optical functions within a single, thin, and compact optical element. They play important roles in various applications, ranging from 3D super-resolution microscopy to virtual and augmented reality; however, their fabrication remains expensive, time-consuming, and reliant on specialized infrastructure such as clean rooms. This is because the elements are built of nanoscale structures in different heights and shapes and require fabrication precision on the order of tens nanometers. Emerging 3D printing methods for optical components have shown significant promise, yet considerable challenges remain. These include inherent trade-offs among device size, fabrication speed, and resolution, as well as difficulties in achieving uniform optical properties (e.g. consistent transparency and refractive index) due to the layer-by-layer nature of the printing process.
Our solution leverages near-index matching to scale DOE feature sizes from hundreds of nanometers to tens or even hundreds of microns. By concatenating two solids (or a solid and a liquid) with refractive indices differing by only about 10⁻³–10⁻², we significantly reduce the refractive index contrast. Consequently, to achieve the same accumulated phase, we proportionally scale up the axial DOE dimensions. We used a commercially available 3D-printing to fabricate a template, subsequently converting it into a transparent optical element using a two-step molding process. Our approach achieves optical performance comparable to conventional nanoscale-structured elements. This method significantly relaxes fabrication tolerances and removes the need for specialized clean-room facilities. As a result, we reduce the time and cost required to fabricate customized DOEs by orders of magnitude, while also increasing design flexibility compared to traditional methods.
Our solution leverages near-index matching to scale DOE feature sizes from hundreds of nanometers to tens or even hundreds of microns. By concatenating two solids (or a solid and a liquid) with refractive indices differing by only about 10⁻³–10⁻², we significantly reduce the refractive index contrast. Consequently, to achieve the same accumulated phase, we proportionally scale up the axial DOE dimensions. We used a commercially available 3D-printing to fabricate a template, subsequently converting it into a transparent optical element using a two-step molding process. Our approach achieves optical performance comparable to conventional nanoscale-structured elements. This method significantly relaxes fabrication tolerances and removes the need for specialized clean-room facilities. As a result, we reduce the time and cost required to fabricate customized DOEs by orders of magnitude, while also increasing design flexibility compared to traditional methods.
Throughout the project, we successfully met all outlined technical and scientific objectives, as detailed below.
Objective 1: Technical Characterization and Development of the fabrication process
We successfully identified suitable pairs of transparent polymers that are near-index-matched (~0.002 refractive index difference), with strong mutual adhesion, minimal inter-layer diffusion, and compatibility with mold-based fabrication. We accurately characterized the dispersion properties of these materials using high-precision refractometry at multiple wavelengths, which is crucial for developing multi-color DOEs. We evaluated the robustness of our solid-on-solid (SoS) DOEs over time and in comparison to simulations. Based on these achievements, we established a robust and well-defined fabrication workflow. This process begins with optical design and the conversion of the DOE phase matrix into a height matrix, followed by microscale template fabrication via 3D printing, and concludes with an optimized two-step casting process using near-index-matched polymers to create the finalized transparent optical element.
Objective 2: Fabrication of Industry-Relevant Proof-of-Concept Elements
We selected several representative applications to showcase the versatility and utility of our technology, including Fresnel microlens arrays, spiral phase plate (SPP), and customized phase masks for super-resolution microscopy, including a dual-color phase mask with highly complex geometry. Each application underwent optical modeling, followed by 3D printing of molds in collaboration with different 3D printing companies (XJet, Litoz, Nano Dimension, etc.), iteratively adjusting refractive index differences to compensate for minor fabrication deviations. We experimentally demonstrated and quantified the performance and long-term stability of our solid-on-solid (SoS) DOEs. Comparative analyses confirmed that our fabricated DOEs achieved performance exceeding 95% photon efficiency compared to traditional lithography-based methods.
Objective 1: Technical Characterization and Development of the fabrication process
We successfully identified suitable pairs of transparent polymers that are near-index-matched (~0.002 refractive index difference), with strong mutual adhesion, minimal inter-layer diffusion, and compatibility with mold-based fabrication. We accurately characterized the dispersion properties of these materials using high-precision refractometry at multiple wavelengths, which is crucial for developing multi-color DOEs. We evaluated the robustness of our solid-on-solid (SoS) DOEs over time and in comparison to simulations. Based on these achievements, we established a robust and well-defined fabrication workflow. This process begins with optical design and the conversion of the DOE phase matrix into a height matrix, followed by microscale template fabrication via 3D printing, and concludes with an optimized two-step casting process using near-index-matched polymers to create the finalized transparent optical element.
Objective 2: Fabrication of Industry-Relevant Proof-of-Concept Elements
We selected several representative applications to showcase the versatility and utility of our technology, including Fresnel microlens arrays, spiral phase plate (SPP), and customized phase masks for super-resolution microscopy, including a dual-color phase mask with highly complex geometry. Each application underwent optical modeling, followed by 3D printing of molds in collaboration with different 3D printing companies (XJet, Litoz, Nano Dimension, etc.), iteratively adjusting refractive index differences to compensate for minor fabrication deviations. We experimentally demonstrated and quantified the performance and long-term stability of our solid-on-solid (SoS) DOEs. Comparative analyses confirmed that our fabricated DOEs achieved performance exceeding 95% photon efficiency compared to traditional lithography-based methods.
The fabrication process we developed represents a transformative advance in the field of DOE fabrication. Unlike traditional lithography-based approaches that are slow, costly, and dependent on specialized clean-room infrastructure, our method enables rapid, low-cost, and highly flexible production of complex DOE components using standard 3D printing and casting workflows with near-index-matched polymers.
This breakthrough is expected to enable the integration of advanced diffractive optics into optical systems that previously could not consider such components due to prohibitive costs and manufacturing constraints. For large companies developing sophisticated optical systems, the ability to produce complex custom DOEs in-house will significantly shorten development cycles, reduce reliance on external suppliers, and lower overall costs. Establishing internal fabrication capabilities will enable faster iteration during design and prototyping, accelerating time-to-market for new products.
Moreover, the high flexibility in design offered by our approach, including the ability to print DOEs on curved surfaces, will enable innovative optical system designs.
Key Needs for Further Uptake and Success:
To achieve widespread adoption of the developed method in the optical industry, it will be essential to demonstrate the full production of DOE components and their successful integration into evolving industrial optical systems. This includes building and validating complete workflows for producing DOEs tailored to specific use cases.
In addition, showcasing the practical establishment of in-house production infrastructure within existing companies will be critical. Demonstration projects should highlight how companies can implement this technology internally to gain strategic advantages in cost, time, and supply chain independence.
Such efforts will build confidence among industry stakeholders, prove the maturity and scalability of the approach, and facilitate its broader adoption as a standard tool.
Overview of Results at Project End:
By the conclusion of the project, we have delivered a robust, reproducible, and highly accessible manufacturing process that replaces complex clean-room fabrication with a straightforward, cost-effective, and scalable production method. Our results demonstrate that advanced DOE designs can be produced quickly, at low cost, and with the optical performance required for demanding applications.
This breakthrough is expected to enable the integration of advanced diffractive optics into optical systems that previously could not consider such components due to prohibitive costs and manufacturing constraints. For large companies developing sophisticated optical systems, the ability to produce complex custom DOEs in-house will significantly shorten development cycles, reduce reliance on external suppliers, and lower overall costs. Establishing internal fabrication capabilities will enable faster iteration during design and prototyping, accelerating time-to-market for new products.
Moreover, the high flexibility in design offered by our approach, including the ability to print DOEs on curved surfaces, will enable innovative optical system designs.
Key Needs for Further Uptake and Success:
To achieve widespread adoption of the developed method in the optical industry, it will be essential to demonstrate the full production of DOE components and their successful integration into evolving industrial optical systems. This includes building and validating complete workflows for producing DOEs tailored to specific use cases.
In addition, showcasing the practical establishment of in-house production infrastructure within existing companies will be critical. Demonstration projects should highlight how companies can implement this technology internally to gain strategic advantages in cost, time, and supply chain independence.
Such efforts will build confidence among industry stakeholders, prove the maturity and scalability of the approach, and facilitate its broader adoption as a standard tool.
Overview of Results at Project End:
By the conclusion of the project, we have delivered a robust, reproducible, and highly accessible manufacturing process that replaces complex clean-room fabrication with a straightforward, cost-effective, and scalable production method. Our results demonstrate that advanced DOE designs can be produced quickly, at low cost, and with the optical performance required for demanding applications.