Toward Near-Perfect Diffractive Optical Elements via Nanoscale 3D Printing

Abstract

Diffractive optical elements (DOEs) are widely applied as compact solutions to generate desired optical patterns in the far field by wavefront shaping. They consist of microscopic structures of varying heights to control the phase of either reflected or transmitted light. However, traditional methods to achieve varying thicknesses of structures for DOEs are tedious, requiring multiple aligned lithographic steps each followed by an etching process. Additionally, the reliance on photomasks precludes rapid prototyping and customization in manufacturing complex and multifunctional surface profiles. To achieve this, we turn to nanoscale 3D printing based on two-photon polymerization lithography (TPL). However, TPL systems lack the precision to pattern diffractive components where subwavelength variations in height and position could lead to observable loss in diffraction efficiency. Here, we employed a lumped TPL parametric model and a workaround patterning strategy to achieve precise 3D printing of DOEs using optimized parameters for laser power, beam scan speed, hatching distance, and slicing distance. In our case study, millimeter scale near-perfect Dammann gratings were fabricated with measured diffraction efficiencies near theoretical limits, laser spot array nonuniformity as low as 1.4%, and power ratio of the zero-order spot as low as 0.4%. Leveraging on the advantages of additive manufacturing inherent to TPL, the 3D-printed optical devices can be applied for precise wavefront shaping, with great potential in all-optical machine learning, virtual reality, motion sensing, and medical imaging.

Full Color and Grayscale Painting with 3D Printed Low-Index Nanopillars

“…Deviations in colors in adjacent write fields are a limitation of the equipment, caused by insufficient precision in determining the interface between the substrate and the resin leading to random height variations (fabrication details in Note S2). The experimental results confirm the effectiveness of controlling HSB through HTP parameters, achieving with high-quality 3D printed nanopillars as laid out in the design strategy of Figure b. In addition, the full color and grayscale 3D prints are readily reproducible with our methods, as also demonstrated in Figure S10.…”

Reconfiguring Colors of Single Relief Structures by Directional Stretching

“…A base layer of 1 µm thickness was added for each writing field in the design to compensate for errors in identifying the interface between the substrate and the resist. [66] After patterning, the samples were developed in poly ethylene glycol methyl ether acetate (5 min), isopropyl alcohol (2 min), and nonafluorobutyl methyl ether (2 min). The sample was placed on a hotplate at 120 °C for 2 min, cooled to room temperature, then spin-coated with a BGL-GZ-83 (Profactor GmbH) anti-sticking layer at 2000 rpm for 30 s, and used as a template afterward.…”

Celebrating 25 Years of IMRE: Research Highlights on Nanomaterials and Nanotechnologies

“…Nano-optics or nanophotonics is a research field that investigates the interaction between light and nanostructures for various applications, such as optical holography, high-resolution color printing, beam shaping, functional optoelectronic devices, etc. IMRE and collaborators have made significant contributions in the development of nanostructures with optical resonances, including metallic nanoantennas with localized plasmon resonance, − dielectric nanoantennas with Mie resonances, − hybrid plasmon–Mie resonance, and leaky waveguide modes. − Lu et al designed Sb 2 S 3 -based antenna arrays, where the designed Mie resonances in the visible regime could be tuned in a reversible manner (Figure A) . These tunable Sb 2 S 3 nanoantenna arrays could enable the next generation of high-resolution reflective color displays, hologram displays, and compact LiDAR systems.…”