Microlenses, and especially microlens arrays (MLA), are commonly used as stand-alone optical components, for beam homogenization and shaping. Or integrated as wafer-level optics (WLO), either on top of light sources for beam shaping, or on top of light or image sensors as light concentrators. Many techniques are available to originate the microlens shape: laser ablation, grayscale lithography, two photon absorption, etc. One common way is to pattern photoresist pillars by photolithography and to melt (reflow) them. We report new advances in thermal reflow mastering addressing its intrinsic limitations and expanding the design capabilities of reflow-based MLAs.

Single- and two-photon absorption are prominent additive manufacturing methods used in 3D light-based printing through polymerization. We propose the dual use of these methods simultaneously to speed up the printing process while maintaining high resolution. We show a blue light-sheet implementation to assist the polymerization by a femtosecond laser. The light-sheet speeds up the printing considerably by reducing the threshold as well as yielding good optical sectioning, and 2PP provides precise and complex structures in micro- and nanometer scales with high resolution. This method offers new possibilities for printing high-resolution 3D structures with a significant improvement in voxel printing speed.

Optical projection system with high numerical apertures (NA) enables high-resolution imaging but also suffers from shorter depth of focus and more pronounced aberrations relative to low NA systems. In microscale volumetric additive manufacturing (VAM), these problems significantly reduce overall optical contrast and geometric fidelity. In this context, holography is a promising 3D imaging method to solve these challenges thanks to its focal point steering and aberration correction capabilities. However, the design of holographic projections for optimal 3D patterning remains a non-trivial ill-posed problem and this design problem is particularly challenging in systems where the material exposure responses from multiple holographic beams are coupled. In this work, we introduce a novel method to co-optimize the phase masks for multiple coupled holographic beams for motionless 3D lithography. We showcase the flexibility of this method through examples of single-shot VAM systems with different modes of response coupling such as photoinhibition and two-photon absorption. Lastly, we discuss how this method can naturally extend to design phase masks for holo-tomographic 3D patterning.

Three-dimensional direct laser writing by photopolymerization is a technique allowing micro- and nanofabrication at the diffraction limit and particularly suited for fabrication on a variety of substrates. This presentation will focus on our recent efforts to generate novel fibre waveguiding structures and metasurfaces interfaced to conventional optical fibres using this technology. The first part of the talk will focus on light cages, assemblies of thin strands of polymer which allow guiding of radiation in an air core centre. The open nature of the cage makes this geometry particularly suited for sensing and explorations of light/matter interactions. The second part will focus on the interfacing of metasurfaces with fibres for applications such as broadband focusing and imaging.

We present a novel photonic structure on the end-face of a polarization-maintaining single-mode optical fiber for broadband vector beam generation, specifically radially and azimuthally polarized beams and modes. The structure, micro-3D printed using 2-photon lithography, is sub-mm long, and features a unique design comprising complex sequential sections. Our unprecedented design enables spatial control over light's intensity profile and polarization at the optical fiber’s output, with potential significant implications for fields such as optical communications, optical trapping, microscopy, and material processing.

Commercial paints have issues with toxicity, environmental instability, and low resolution. Researchers have proposed nanostructured materials as eco-friendly coloration alternatives. However, existing demonstrations face challenges such as sensitivity to angles, polarizations, limited saturation, and impractical industrial integration. We present a self-standing structural coloration approach that exploits plasmonic resonances to produce a comprehensive color range, providing a vivid and rich palette, with angle and polarization independence. Our ultralight paint, weighing only 0.4 g/m2, is fabricated through large-scale techniques, bridging the gap to real-world industrial applications for non-toxic, fade-resistant, and environmentally friendly structural color.

Ammonia, a major water pollutant, enters aquatic environments from various sources, impacting aquatic life with toxic effects and promoting algae growth. Detecting dissolved ammonia is crucial due to health risks and harm to ecosystems. A nanoplasmonic colorimetric sensor was developed, utilizing metallic nanostructures to change color based on ammonia concentrations, providing a simple and affordable real-time analysis method. The sensor uses aluminum and aluminum oxide, avoiding toxic chemicals. A smartphone application was also developed as a robust protocol for quantifying ammonia in aqueous solutions, eliminating the need for optical instruments and facilitating on-site monitoring.

We developed a series of photo-curable liquid resins containing silsesquioxane or silsesquioxane-structured molecules, which were subsequently utilized in a two-photon polymerization printing strategy. The printed structures underwent a controlled thermal treatment, converting them into inorganic glass while maintaining a temperature below the glass transition temperature of silica. Our investigation focused on elucidating the influence of the molecular composition of the resin on its intrinsic properties, print quality, and dimensional changes during the thermal conversion process. Our results underscore the capability of this approach to fabricate micro-optics with exceptional precision and complexity, thereby showcasing its potential for advancing micro-optical device fabrication.

We will report our research trials for the non-sintering, low shrinkage, and user-friendly two-photon polymerization printing technology for high-resolution complex glass optical system development, including multi-lens objective and endoscope, movable zooming lens pair, spectrometer, and bio-inspired snapshot hyperspectral imaging system. We will introduce our previous and recent publications for more micro-glass optics potential.

Macromolecules with complex, defined structures exist in nature (e.g. DNA, RNA and proteins) and their remarkable functionality is dictated by their intricate hierarchical structure. Nevertheless, achieving such a high level of precision at the molecular level remains impossible using conventional materials for two-photon 3D laser printing. Herein, we present our recent work in the field, with emphasis on engineering of precisely-defined and self-assembled materials using a nature-inspired approach. Through the precise control and printability of these materials, an exciting avenue for the manufacturing of functional materials with distinct properties and nanostructure is established.

We have realized active microoptics using the temperature-responsive polymer PNIPAAM. We demonstrate refocusing a 3D printed microlens by thermal activation. Furthermore, we demonstrate ultralarge optics using gray scale lithography. We also demonstrate compact optical trapping devices using 3D printed assemblies. 3D holography directly on the tip of fibers enables complex beam shapes. Additionally, we report on interferometric wavefront testing, demonstrating ultrahigh optics quality with Strehl ratios beyond 0.95. Quantum applications such as coupling of quantum emitters into single mode fibers as well as coupling single mode fibers to ultrasmall superconducting detectors are also reported.

We present a novel design for an electrically tunable focus (ETF) FZP lens device in a dielectric medium. This metal lens benefits from SPP enhancement in addition to ETF properties . These devices are fabricated using a simplified one-step direct laser writing (DLW) process that exploits photoreduction in a transparent metal salt enriched growth medium. The setup uses 800 nm MaiTai laser with a 90 fs laser pulse. Few mw pulses are focused using high NA objective on a sample mounted on a high resolution 3D stage. This device shows immense potential in various fields, including micro/nano photonics, machine vision, and AR/VR applications.

Material measures, crucial for calibrating measuring instruments in metrology, face limitations due to their standardized categorization as being either profile kind or areal kind. To ensure comparability and uncertainty estimation across different measuring instruments, we explore to adapt these material measures (reflective micro-optics) for multiple types of instruments using additive manufacturing on the microscale - namely direct laser writing. This flexible technology allows to extend profiled material measures to be usable for areal surface topography instruments and vice versa. The thus revised micro-structures are designed, manufactured, and measured to practically demonstrate the possibilities for a multifunctional calibration of different measuring instrument categories, as well as to illustrate the effect of directionality on the results. Moreover, fortunately, 3D µ-printing enables the fabrication of all structures on a single sample, reducing costs and time for the calibration tasks in research and industry.

Light-based 3D printing shows great potential in biomedical applications by providing high-resolution features. However, its high-resolution capability is severely hindered in 3D printing through biological tissues because of the optically turbid nature of the tissue. Here, we demonstrate a high-resolution additive manufacturing technique through scattering media using upconversion nanoparticles (UCNPs) and the wavefront shaping method. It uses near-infrared (NIR) light to photopolymerize through the scattering media via UCNPs, which act as a secondary source for UV light as well as a beacon for wavefront shaping. By exploiting the optical nonlinearity of the upconverted fluorescence and the memory effect correlations, high-resolution printing is experimentally demonstrated through strongly scattering layers and biological tissues even when the signal is not localized. This technique provides a proof of concept of 3D printing through turbid media with potential applications for in vivo 3D bioprinting.

Adaptive optics allows for spatial control over the phase and intensity of a laser beam, making it a powerful tool to assist ultrashort pulse laser machining. Optical aberrations caused by refraction at interfaces distort the laser focus, compromising resolution and fabrication efficiency. We show how the aberrations can be dynamically compensated using adaptive optics, such as liquid crystal spatial light modulators, for improved manufacturing of functional devices. Examples include fabrication of waveguide circuits in a range of materials, fiber based Bragg sensors for harsh environments, diamond based electronics and compact tunable liquid crystal devices.

In-situ monitoring and characterization systems play a pivotal role in advancing the state of the art in manufacturing and the associated qualification of processes and materials. Here we present a highly sensitive optical imaging method based on quantitative phase imaging for in-situ monitoring the tomographic volumetric additive manufacturing process. The proposed method can visualize the manufacturing process with higher sensitivity and contrast for materials with low refractive index change after polymerization. The information provided by quantitative phase imaging system will be useful for quantifying the underlying material properties and optimizing the polymerization process.

We present a new image generation algorithm for volumetric additive manufacturing that improves computational efficiency while including scattering and diffusion. Traditional binary dose targets are shown to generate uncorrectable errors motivating a target smoothed to achievable resolution. These are combined with a new optimization algorithm to demonstrate rapid convergence to error-free solutions.

We present the option to use the patented [1, 2] Computer Generated Holography (CGH) modality, HoloTile, as a better alternative light delivery system for volumetric additive manufacturing (VAM). Holographic light delivery promises many of the qualities sought after in VAM, including higher photon efficiency, inherent wavefront shaping, full point spread function control, and lower mechanical complexity. These qualities, along with the unique control that is gained with HoloTile, may allow for the use of low-power light sources at low print times with real-time aberration and scattering compensation.

Light-based technologies for 3D printing have recently been developed and are leading the field thanks to their unmatched performance. However, these techniques are still limited to using incoherent light patterning for printing. Here, we present a novel approach that allows us to print using coherent patterns by combining light-beam shaping and tomographic projections. We demonstrate this concept with a volumetric printer based on reverse tomography using a Digital Micromirror Device (DMD) in a holographic configuration. The Lee holograms method allowed us to use the DMD as a fast phase modulator and the HoloTile approach to achieve fast and speckle-reduced holograms.

Volumetric additive manufacturing (VAM) is a newly developed polymer 3D printing technique that uses tomographic light patterns to fabricate complex 3D objects all-at-once. This volumetric printing platform, however, introduces challenges with photoresin requirements. In this presentation, we will discuss the constraints imposed by VAM on the photoresins and the strategies we are using to circumvent these constraints. The advances, made by understanding the dynamics of acrylate-based chain growth polymerization in 3D volumes, have led to photoresins capable of printing larger objects four times faster with higher resolution. These breakthroughs in photoresin formulations significantly broadens the application space for VAM as it can generate intricate polymer objects with exceptional print fidelity with surface finishes of optical quality.

Volumetric additive manufacturing (VAM) is an optical 3D printing technique in which patterned light is projected into a photoactive resin from multiple angles. The patterned light is chosen to solidify the resin in a specified 3D shape. A typical VAM printer consists of 3 main components – a projection system, a rotation mechanism, and a cylindrical vial of resin mechanically fixed to the rotation mechanism. Typically, the alignment of the projection system and rotation mechanism are completed prior to any printing while the alignment of the vial is done print by print. The vial alignment is often tedious, time consuming, and is error prone, thus decreasing the throughput of the printer. Additionally, alignment errors cause decreased print volume and resolution. In this work, we show a novel technique to detect the relative alignments of these 3 systems and then electronically correct for the misalignments which maximizes print volume and resolution.

The optical design, computation, and material formulation that support roll-to-roll tomographic volumetric additive manufacturing (VAM), a continuous VAM process, are described. Results from initial printing trials are presented.

Photoactivated Reversible Deactivation Radical Polymerization (RDRP) technologies have emerged very recently in the field of 3D printing systems especially at the macroscale in vat-photopolymerization-based processes such as digital light processing (DLP). Contrary to conventional free radical photopolymerization, photoRDRP in 3D printing leads to 3D objects with living character and thus confers them the unique ability to be post-modified after fabrication. While 3D direct laser writing (3D DLW) by two-photon polymerization has become a standard for fabrication of complex 3D micro-objects, the use of photoRDRP and its associated benefits has so far been under investigated at that scale. In this communication, I will present our recent results in this field, highlighting the key role of (macro-)photoinitiator in photopolymerization and their importance to open new perspectives in multi-material and 4D micro-printing.

Computed Axial Lithography (CAL) is a promising manufacturing technique for microscale optical elements. CAL would also be attractive for custom macroscopic (centimeter-scale) optical components because of its speed and ability to work with a wide range of photopolymer precursors. However, the imaging performance of lenses printed with CAL is impacted by surface profile errors that are on the order of the projected pixel size. To develop CAL for manufacturing optics, this form error needs to be reduced through further optimization of the delivered light dose distribution and improved control of exposure and postprocessing parameters. Using a plano-convex model geometry, we formulated a simulation model that accurately predicts the height profile of a printed lens surface. We elucidate the important role of the diffusion of oxygen or radical scavengers during polymerization in determining the final shape of a printed lens. We have developed an optimization framework that corrects form errors by harnessing mass transport effects. The framework simulates the form error via an interpolation scheme that tracks a relevant objective function (degree of oxygen depletion or polymerization) at the exact surface points of a lens rather than on the grid points of a voxelized reconstruction. We will demonstrate simulation results of reduced form error at both pixel and sub-pixel sized scale as well as experimental results of improved lenses printed by optimized projection sets. We expect our algorithms will also advance CAL in other precision manufacturing applications and printing for materials with high diffusivity such as hydrogel.

We present a new technique for fabricating smooth parts using volumetric additive manufacturing. In this work, we show that intentional blurring of the writing beams eliminates discretization and layer-like artifacts, resulting in optically-smooth surfaces. Lenses produced with this technique show comparable imaging performance to commercial glass elements, underpinning the value this direct printing approach offers. We anticipate that our blurred tomographic approach will be beneficial for the rapid prototyping of low-cost, freeform optical components.

Meta-optics have been gaining momentum in the last few years. The meta-atoms for IR range applications are large enough and can be patterned by traditional semiconductor lithography. Making meta-optics in the visible range of 400 to 600nm, the meta-atom structures become too small and the optical lithography falls short. Moxtek has established a manufacturing line enabled by nanoimprint lithography (NIL) that can pattern and build visible range meta-optics. This process has shown proven total efficiency greater than 90% at 532nm wavelength on a baseline over multiple lots. This data set for visible meta-optics, confirms that volume manufacturing of visible wavelength metalens is possible and the patterning barrier has been removed.

We present the results of an extended study on the evolution of dicing blade dynamics to define the tolerances of the ductile regime for dicing optical quality facets with sub-nm surface roughness in optical materials. These results provide a route to determine the critical parameters, such as depth of cut, blade shape, and feed rate, to maintain stable ductile machining within a specific range of conditions. We will discuss our latest results and observations, including optical characterisation of waveguides in lithium niobate and other materials.

The force governs the physical world. However, revealing the secrets of nature is not a simple matter. Apart from ordinary physical issues, many nonlinear processes (fluid mechanics, electromagnetic problems, etc.) provide more complicated metrix. These eye-catching but complex phenomena are all related to force. Thus, precisely measuring the force is of fundamental importance to unveil the hidden sciences for a wide of applications. However, advanced instrumentations like atomic force microscope (AFM) cannot best fit the sample sizes, and other specifically-developed MEMS/NEMS fail on universal occasions. Here, we present a fiber-integrated force probe using a spring-composed Fabry-Perot cavity for general-use purposes. The force-sensitivity and resolution reach values of 0.43 nm/nN and 35.79 pN, respectively, representing the highest precisions among all fiber-based nanomechanical probes so far. Typically, we use the proposed sensor to preliminarily explore the micro scale nonlinear problems in fluid mechanics. Further customized its geometries and properties, we anticipate the easy-to-use force probe would generate significant impacts for accurate force-detection.