This PDF file contains the front matter associated with SPIE Proceedings Volume 12412, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

In recent times, much of the world has suffered from supply chain difficulties that have affected shipments and deliveries of food, medicine and equipment. In manufacturing, supply chain issues have resulted in delays due to a lack of materials and parts, as well as from a lack of skilled labor. It is reassuring however, to know that Additive Manufacturing (AM) and Laser AM in particular, create the potential to overcome some of these difficulties. 3D printing by Laser Powder Bed Fusion and/or Laser DED are ideal processes for manufacturing near or at the point of end use. A significant lead time advantage can be achieved through the adoption of these processes and even reduce the carbon footprint associated with production, which also decreases waste and makes financial sense.

Single-photon multi-wavelength polymerization reactions were previously shown to break the diffraction limit in 2D lithography and in some cases used to implement 3D printing techniques. We exploit these types of reactions in combination with a computer driven full-field irradiation method to implement a highly parallel threedimensional micro-fabrication technique. In this manuscript we are presenting the analysis of the advantages and limitations of the method comparing to the state-of-the-art. We believe that, due to high speed and low cost, this fabrication approach will shift the paradigm of micro-3D printing from prototyping and R&D applications to serial production.

In laser powder bed-based metal 3D printing, the high cooling rates in the process have advantages or disadvantages depending on the used material. For unique materials like amorphous metals the high cooling rate is a big advantage. However, the high cooling rates can also lead to very high stresses in other materials like titanium. Preheating the system to 500°C enables the processing of special titanium alloys such as Ti6242. Applying additive manufacturing to conventionally produced parts allow the combination of multiple materials. The feasibility of material combinations using this technique depends on individual material properties. With adapted process strategies, different materials can be combined.

Engineered optics are an important aspect of the evolution of laser additive manufacturing (LAM) where they play a critical role in enabling higher print speeds and resolution. Historically, the use of off-the-shelf optics came with performance trade-offs that offered limited design options to manufacturers. With increasingly complex part geometries and the need to print finer features with and higher density using high power lasers, novel optical designs will play a vital part in advancing LAM technology. This paper will discuss optical design considerations for LAM and will provide an introduction to advances in optics that enable the next generation of high-power LAM printers.

The innovative use of integrative additive manufacturing with special materials opens up new possibilities through greater functionality as well as component integration. For this purpose, multifunctional optomechanical assemblies consisting of multiple materials are additively manufactured via laser metal deposition (DED-LB/M). A particular challenge in terms of process technology is the connection between incompatible metallic and ceramic materials as well as the connection with optical components. These connections are relevant in electro mobility and for the production of laser-optical systems. The successful generation of these 3D-structures made from an adapted molybdenum-copper-phosphor material system leads to the reduction of thermal expansion differences between the components in multimaterial combinations. This is the basis for reducing thermally induced mechanical stresses in the operation of laser-optical or high-power electronic systems. The evaluation reveals several significant process influences and mathematical prediction models are created. These models are used to determine suitable laser settings. The combination of the determined process settings and the adapted molybdenum-copper-phosphor material enables the additive manufacturing of property-adapted pseudoalloys. With the developed process strategy, it has been possible to bond test specimens to metal and thus additively create first multimaterial prototypes by means of laser metal deposition.

Additive Manufacturing (3D printing) is now an accepted form of manufacturing for a range of applications but in particular, laser AM for space exploration has become an exciting application. Additive processes including EBAM (Electron Beam Additive Manufacturing), WAAM (Wire Arc Additive Manufacturing) and laser hybrid arc have been demonstrated for fuel tanks, barrels and other structures but to really explore our solar system and beyond, we need to focus on better ways to print propulsion devices for launch vehicles. Laser powder bed fusion (also called Laser Metal Fusion – LMF) and laser DED (also called Laser Metal Deposition - LMD) are the tools to help us achieve these lofty goals. A method combining both LMF and LMD to create an additively manufactured rocket engine injector and nozzle, (example of a complicated propulsion device), was taken on by TRUMPF’s laser application lab in Plymouth, MI. We started this project work off with an injector designed to be printed in GR Cop 42, a copper alloy developed by NASA, that provides improved thermal conductivity with printability in laser metal fusion powder bed machines. A green laser optic was used for this powder bed process. We then utilized laser metal deposition process to print a wide-bell-shaped nozzle for the exhaust gases. The advantage of combining both processes gave us the intricate cooling channel design for fluid flow inside the injector chamber, along with thin wall features. The freeform nature of laser metal deposition allows a wide flared bell shape to be printed without the constraints of a powder bed.

Laser induced forward transfer (LIFT) and laser sintering of metal nanoparticle inks constitute a two-step digital fabrication technique which has been proven a key enabling technology for the fabrication of flexible microelectronic devices. In this work we will present the investigation of the laser printing and sintering process of Ag nanoparticle inks for the production of a conductive grid comprised of parallel lines as replacement for the bottom Indium Tin Oxide (ITO) electrode in organic photovoltaics (OPVs). We study the effect of a range of laser parameters and their impact on the morphological characteristics and the electrical performance of the laser printed conductive grid. The electrical conductivity of the laser printed lines is calculated by means of electrical measurements in a 4-point probe IV station while their morphological characteristics are assessed with profilometry measurements. As a result, flexible ITO-free OPVs incorporating laser-printed Ag grids as a bottom electrode on PET substrates will be presented. The results confirm that the laser printing and sintering combination is an advantageous technique, which can offer a distinguishing solution for applications in highly efficient ITO-free OPVs.

Nanoelectrospray laser deposition (NELD) of semiconductor and metal nanoparticles is a powerful and potential technology for the on-demand printing of precise and complex functional microarchitectures. In this study, a CO₂ laser is used to deposit and sinter titanium dioxide (TiO₂) nanoparticles on borosilicate and quartz substrates for transparent film applications. The CO₂ laser is chosen for sintering because TiO₂ has a lower spectral absorption at 10.6 μm wavelength. Therefore, the 10.6 μm laser can transmit through the deposited TiO₂ films, and then, the whole film thickness can be thermally modified by the heating effect of laser. The effects of wet-deposition process parameters and laser processing parameters on the morphological, optical, and structural properties of TiO₂ patterns are examined. The TiO₂ microstructure and surface morphology were studied by optical and scanning electron microscopy techniques. X-ray diffraction (XRD) was used to investigate the structural characteristics after laser sintering. The optical transmittance of the wet and sintered TiO₂ films was characterized by UV/Vis/NIR spectrophotometry. We established that the overall improvement of the morphological and optical properties of the sintered films originates from the enhanced bonding and physical interconnectivity of TiO₂ nanoparticles, resulting in the formation of a dense and compact ceramic layer. XRD data points out that the anatase phase of TiO₂ is preserved after laser sintering, eliminating the presence of TiO₂ rutile traces. An average transmittance above ~90% was achieved in the NIR region.

Single-mode, multi-fiber expanded-beam connectors (EBCs) were fabricated based on a two-step process using coreless glass fibers and two-photon polymerization (TTP) 3D printing technique. First, coreless glass fibers were spliced onto a single-mode fiber ribbon and then precisely laser-cleaved to the ideal length. A micro-lens array was directly laser printed onto the coreless fiber extensions using the TPP technique to create the expanded, collimated output beam. Coupling loss measurements at 1310 nm between two 3D-printed EBCs matched the results of simulations. The high spatial resolution of the TPP technique avoids cumbersome active alignment procedures, and thus enables low-cost, high-throughput optical connectivity solutions.

Copper has been widely applied for various industrial components such as heat exchangers, heat pipes, electro circuits and motors for automobiles because of having excellent properties in thermal conductivity and electrical conductivity. But it is difficult to process pure copper with IR lasers since light absorption of copper has 10% or less. It is known that he light absorption for copper increases as the wavelength becomes shorter. Thus, it was focused on 450 nm wavelength blue diode laser. In our previous study, multi beam type LMD method has been developed using a high intensity blue diode laser for copper layer formation and formed pure copper layer. However, pure copper was oxidized in the air and its surface turns black. Therefore, we tried to coat copper alloy with Zinc added (80% Cu-20% Zn) to improve discoloration resistance. And we tried to investigate of copper alloy layer mechanism using high speed camera. As the result, Cu-Zn alloy layer was formed on the stainless-steel plate with no pores at the output power density of 0.57 x10⁵ W/cm² and scanning speed of 6mm/s.