Light projection displays play an increasingly important role in our modern life. Core projection systems including liquid crystal displays and digital micromirror devices can impose spatial light modulation and actively shape light waves. Recently, the advent of metasurfaces has revolutionized the design concepts in display technologies, enabling a new family of optical elements with exceptional degrees of freedom. In this talk, we will present examples of electrically-controlled metasurfaces for dynamic holographic displays. We will also outline the possibility to achieve programmability and addressability of optical metasurface devices at the single pixel level.

The invariant longitudinal spatial profile of the Bessel beam makes it attractive for laser processing. We show a fast and simple process to generate high aspect ratio nano-pillars using a single ultrafast pulse shaped as higher order Bessel beam. The high pressure induced in the sapphire bulk results in the ejection of elongated structures. These nano-pillars can exceed 15 μm in height with a sub-μm diameter. The observed morphologies suggest a model with different material ejection processes, ranging from solid material extraction to hydrodynamic jets. High-resolution transmission electron microscopy of the crystalline structure provides support for our proposed model.

Femtosecond laser processing in GHz-burst mode has attracted much attention. Here, we report on dielectrics cutting with a spatially and temporally shaped femtosecond laser beam using a Bessel beam in the GHz-burst regime. In this contribution, we report on the influence of the number of pulses per burst as well as the pulse duration of the individual pulses within the burst. The resulting surface roughness of the cutting planes is measured as a function of the cutting parameters to evaluate the cutting quality.

Dielectrics cutting with Bessel beams formed by an axicon is nowadays a well-known technique. Typically, the axicon is used in transmission to form the elongated Bessel beam. In this contribution, we report on dielectrics cutting with a femtosecond laser using a reflective axicon and compare the results in terms of surface roughness of the cutting planes with those obtained with a standard refractive axicon. Moreover, we couple the spatial beam shaping with temporal beam shaping applying MHz- and GHz-bursts of femtosecond pluses.

We demonstrate nano-structuring and the reduction of mid-spatial-frequency (MSF) errors using femtosecond laser figuring and finishing. We established a method to create periodic nanostructures using femtosecond-laser-based ablation. In addition, a laser-created sinusoidal pattern with five cycles/mm was generated to mimic the mid-spatial frequency error that often occurs s during conventional optics fabrication. A deterministic material removal having nanometer-scale precision was performed to remove the mid-spatial-frequency error from 17 nm to one nanometer in magnitude. The resulting surface remains single-digit-nanometer surface roughness after the MSF error correction.

Despite the development in various Additive Manufacturing (AM) techniques, there still remains a challenge for fabricating complex structures composed of alternating metallic and dielectric structures with high-resolution. Two AM techniques are presented that use light to initiate various chemical reactions to print high-resolution, multimaterial 3D structures: advanced Digital Light Processing (DLP) and Stereolithography (SLA) via multiphoton-reduction. First study demonstrates fabrication of heterogeneous structures using a custom-built DLP printer. By combining an innovative multi-material DLP printing method with studies on carbon-filled composite photopolymers, carbon nanocomposite multi-material structures are 3D printed in a low-cost manner. Second study demonstrates fabrication of high-resolution connected and/or disconnected 3D metallic structures embedded in a dielectric matrix using a femtosecond direct laser writing technique. This technique simplifies the fabrication process, opening new possibilities for multimaterial, multilayer printing application/devices.

We fabricated hierarchical glass biochips with interior characteristics that can be tailored by adjusting process parameters. By a new derived processing method, termed Femtosecond Laser Assisted chemical Etching Nanoscale Glass Deformation (FLAE-NGD), we have developed graded and hierarchical configurations with dimensions from several hundred micrometers to several hundred nanometers as relevant glass model platforms that mimic cancer cell intravasation-extravasation processes. We were able to control the dimensions of both the widths and lengths of the channels as well as shape and curvatures of interior glass pillars. Various curvatures were successfully prepared for the study of the migration and invasion processes of cancer. We have further evaluated the effect of x-ray exposure on melanoma cells grown in glass biochips and determined the increase of intracellular reactive oxygen species production and cellular DNA breaks with the applied irradiation dose.

Industrial grade ultrashort pulsed USP laser systems offer pulse durations of about 300 fs and higher whereas shorter pulse durations could only be achieved with research systems, as e.g. Ti:Sapphire, lacking from stability and high repetition rates as demanded for industrial laser micro processing. Former experiments showed that on the one hand and improve of the energy specific volume (process efficiency) can be achieved with shorter pulses especially for steels. On the other hand, an ablation regime with very smooth surfaces on soda-lime glass was observed with pulses shorter than about 500 fs. Thus, it is worth to investigate the sub 100 fs regime for industrial laser micromachining processes. We will show first results from basic investigations concerning the energy specific volume, the surface quality and the minimum achievable structure size for metals, semiconductors and glasses with an industrial grade NKT Aeropulse system at a waveleng6th of 1030 nm in combination with MIKS1 S pulse compressor from N2 Photonics (offering sub 100 fs pulses) and a high-end galvo scanner from Scanlab for repetition rates up to 1.2 MHz.

Adaptive optics for compensating for wavefront aberrations have been reported in astronomy, optical coherence tomography, microscope imaging, and laser material processing because the aberrations cause focal spot distortion leading to loss of resolution and efficiency in these applications. In adaptive optics, wavefront sensing is important. Several approaches for wavefront sensing have been demonstrated, such as a Shack–Hartmann wavefront sensor, shearing interferometry, the Transport-of-Intensity Equation (TIE), and iterative algorithms for phase retrieval. In this presentation, femtosecond laser processing with aberration compensation based on machine learning was demonstrated. The aberrations existing in the laser processing were continuously predicted by the trained neural network with an update period of 36 ms and were compensated by a spatial light modulator. In the experiment, the neural network-based adaptive optics reduced the wavefront error in the laser processing to most one-ninth. Therefore, the adaptive optics improved the resolution in laser processing.

Existing auto-focusing methods in laser processing typically include two independent modules: surface detection and z-axis adjustment. The latter is mostly implemented by mechanical z-stage motion, which is up to three orders of magnitude slower than the lateral processing speed. To alleviate this processing bottleneck, we developed a single-lens approach, using only one high-speed z-scanning optical element, to accomplish both in-situ surface detection and focus control quasi-simultaneously in a dual-beam setup. Our approach provides instantaneous surface tracking by collecting position information and executing focal control both at 140-350 kHz, which significantly accelerates the z-alignment process and offers great potential for enhancing the speed of advanced manufacturing processes in three-dimensional space.

The fabrication of multicomponent devices presents a challenge when facing the densification process. In the case of a microcapacitor, it involves a matrix of a dielectric componenet, such a Barium Titanate (BTO), sandwiched between electrodes for which a metallic material is commonly used. The material phases involved possesses different thermal properties which make impossible to densify at the same temperature and time. The combination of different laser technologies such as Laser-Induced Forward Transfer (LIFT) and Selective Laser Sintering (SLS) could be the key to fabricate these multicomponent devices by using digitazable technologies. In previous works the LIFT deposition and the Selective Laser Sintering of BTO has been prospected. Only superficial densification has been obtained on the dielectric component by SLS. In this work, LIFT and conventional sintering of BTO combined with the LIFT deposition and SLS of silver pastes are proposed for the fabrication of a first prototype.

Recently, we published our early results on laser microprinting of functional microelectronics (Nature Commun. 14, 1103 (2023)). Here, we report our progress beyond this work. First, we present a simplified photothermal print scheme – again without the need for post-processing. This scheme includes the purposeful choice of the printing substrate as well as new inks. Second, we present our early results on in-situ monitoring of the metal- and semiconductor-growth processes by time-resolving a weak co-focused reflected probe laser beam. Third, we discuss how the print parameters such as focus speed and laser power influence the morphology of the printed material.

As a platform for high resolution bioimaging, biochips with a refractive index very close to that of a culture medium (water) are highly demanded. CYTOP (AGC Corporation) is a promising material, since its refractive index (1.34) is almost similar to that of water (1.33). However, high transparency in also the ultraviolet region and high chemical resistance of CYTOP make it difficult to fabricate 3D microstructures for biochips. In this study we present fabrication method of 3D biochips based on CYTOP for cell observation by the molding process using 3D micro/nanostructures fabricated by two-photon polymerization with femtosecond laser.

Femtosecond Laser Direct Write (fs-LDW) is a promising technique for fine 3D printing of biomaterials such as protein due to nonlinear multiphoton absorption processes facilitating microfabrication along a designated laser light path. Proteinaceous microstructures fabricated by fs-LDW are reported to retain their native protein function. Combined with submicron feature sizes, they might offer diverse biomedical or biochip applications. Here, we show that some amino acids are beneficial to the fabrication process. From our investigation of eight commercially available homopeptides, we found new insights into the fabrication mechanism. The beneficial amino acids could be useful to enhance future 3D printing processes.

Laser scribing is a promising technology for thin-film ablation in photovoltaic device manufacturing, particularly with non-conventional materials. This study explores copper oxides as alternative light absorbers due to their abundance and safe sourcing. Transition metal oxide (TMO) layers, like molybdenum oxide (MoO3), vanadium oxide (V2O5), and tungsten oxide (WO3), are investigated as selective contacts for advanced semiconductor devices. The research employs a high-powered fs laser (EKSPLA FemtoLux30, 30W, 1030 nm) with tunable pulse lengths (350 fs~1ps) and various wavelengths (1064, 532, and 355 nm) to determine the threshold ablation fluence and achieve optimal thin-film removal without substrate alteration. Diode isolation and electrical characteristics demonstrate the process's high quality.

The targeted and timely delivery of light at precise locations on a sample is central for laser materials processing. However, such a task can be limited by the optical properties of the sample or the mechanical inertia of systems required to focus, split or move the light. Here, I will show how ultrasound in liquids can address these issues and achieve rapid and precise 3D control of light, even inside scattering media. The gist of our approach is based on exploiting the acousto-optic effect in liquid-filled ultrasonic cavities. By properly selecting the geometry of the cavity, light guiding, splitting, and Bessel-beam shaping can be achieved at sub-microsecond timescales. Our results are a promising step toward on-demand and high-throughput additive and subtractive microfabrication.

The use of lasers for Printed Circuit Board (PCB) manufacturing continues to grow as their cost-per-Watt goes down and power levels go up. Furthermore, many lasers now offer features such as temporal pulse tailoring, which is often beneficial. In this work, we demonstrate several PCB processes using UV and green high-power ns-pulse lasers. In addition to cutting thicker FR4, cutting of system in package (SiP) material is demonstrated, and a process using advanced temporal pulse tailoring with 100 W of UV single-mode laser power for percussion flex-PCB via-drilling is demonstrated for a ~50 μm hole diameter.

In laser processing, the intensity distribution of the laser beam affects the crater formation and the distribution of ablated particles ejection. In this study, we demonstrated the ejection control of semiconductor microdroplets such as the droplet size and ejection direction by irradiation of the target substrate using a ring-shaped pulsed laser. In addition, we demonstrated the suppression of spatter generation in laser welding of metals with support from the ring-shaped beam.