Recent Advances on High‐Speed and Holographic Two‐Photon Direct Laser Writing

Abstract

Two‐Photon Lithography, thanks to its very high sub‐diffraction resolution, has become the lithographic technique par excellence in applications requiring small feature sizes and complex 3D pattering. Despite this, the fabrication times required for extended structures remain much longer than those of other competing techniques (UV mask lithography, nanoimprinting, etc.). Its low throughput prevents its wide adoption in industrial applications. To increase it, over the years different solutions have been proposed, although their usage is difficult to generalize and may be limited depending on the specific application. A promising strategy to further increase the throughput of Two‐Photon Lithography, opening a concrete window for its adoption in industry, lies in its combination with holography approaches: in this way it is possible to generate dozens of foci from a single laser beam, thus parallelizing the fabrication of periodic structures, or to engineer the intensity distribution on the writing plane in a complex way, obtaining 3D microstructures with a single exposure. Here, the fundamental concepts behind high‐speed Two‐Photon Lithography and its combination with holography are discussed, and the literary production of recent years that exploits such techniques is reviewed, and contextualized according to the topic covered.

Novel technologies to micro and nanostructure highly nonplanar optical fibers: from the micro to the sub-50 nm regime

“…To overcome these limitations, alternative techniques such as UV laser ablation of Parylene could be considered to replace dielectric milling, while electrodeposition processes could substitute for Ion Beam-Induced Deposition (IBID). Additionally, the rising interest in holographic TPP 39 (Holo-TPP) could allow to generate multiple foci to parallelize the patterning of the photoresist up to five times, with a reduction of the fabrication times of the same factor.…”

Photochemically Activated 3D Printing Inks: Current Status, Challenges, and Opportunities

“…In general, photoresists can be separated into two groups, that is, positive‐tone and negative‐tone resists ( Figure a). [ 39 ] For positive‐tone, the photoresist is typically spin‐coated onto a glass substrate. Thus, the desired thickness of the photoresist is controlled by the spinning speed and the time for pre‐exposure baking, which occurs immediately after the spinning.…”

Effective Approach for Fabricating Highly Precise High-Curvature Structural Patterns via Air-Bubble Induction

“…In recent years, the interest in patterning techniques capable of effectively mass-producing large-area, regular, and periodic nano/micro-structures has increased rapidly. In particular, a process for fabricating regular and precise micropatterns with a three-dimensional (3D) curved structure has been developed. − Because a regular 3D curved structure can be used to control the pathway of light, selectively absorb or reflect specific wavelengths, store a specific material, and significantly increase the surface area, it can promote innovative development in various applications, such as microlenses, photovoltaic cells, biosensors, OLEDs, photonic crystals, and adhesive pads. − Various patterning techniques, such as colloidal lithography, − thermal reflow, , photolithography-based isotropic wet etching process, , and gray-scale lithography, have been reported to produce regular 3D curved structures at the micrometer scale. Colloidal lithography can implement a 3D nano/micro-pattern with a curved structure; however, this technique is limited in its application to practical industrial-scale processes.…”