This PDF file contains the front matter associated with SPIE Proceedings Volume 12135, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

Additive Manufacturing (AM) processes improved to such an extent, that they are now applied for production of optical elements like lenses, mirrors and light guides. However, since the quality of these manufacturing processes still does not meet typical surface roughness specifications for optical surfaces, except on the micrometer scale, additional effort for post processing is required. It is therefore more convenient to use the potential of AM to build the mounting structures of optical systems and use more suitable technologies for the optical surface production. For that reason, we develop additively manufactured and monolithic mounting structures using the design freedom and flexibility of AM and combine them with macroscopic lenses of excellent optical quality. To evaluate our concept, we measured the modulation transfer function (MTF) of a commercial photo lens. We replaced its mounting structure with our additively manufactured and monolithic one and measured the MTF again. It could be demonstrated that the replaced mounting structure has a nearly identical optical performance and even an improvement in the off-axis fields, due to less tolerance chains.

The possibility of large-scale part fabrication is the biggest novelty factor associated with Directed Energy Deposition (DED) Additive Manufacturing (AM) technology. However, issues like deformation and residual stresses in the fabricated part originated from DED process physics are still hindering the possibility of large-scale part fabrication. To overcome these bottlenecks, a DED process simulation that predicts the thermo-mechanical response of the material/workpiece can be a useful tool. There are some conventional simulation techniques that are employed commonly for other technologies like welding or Powder Bed Fusion (PBF). But using the same simulation methodologies for the DED process will lead to impractical computation time or inaccurate results. Hence, in the present work, an efficient simulation methodology dedicated to DED is proposed. The proposed model reduces the computation time drastically and also keeps the desired computation accuracy levels. An equivalent heat source is employed that efficiently models the material deposition along with the programmed deposition strategy. The inclusion of deposition strategy in the efficient model is very important for model accuracy, as deposition strategy plays a critical role in the thermo-mechanical response of the deposited material. The proposed model is developed and implemented in COMSOL Multiphysics. With a cantilever tooling, multiple Stainless Steel 316L (SS 316L) thin wall builds of 50- and 100-layers high is fabricated. Numerical results predicted with the efficient model are successfully compared with experimental data such as thermocouple’s in-situ temperature recordings and Laser Displacement Sensor’s in-situ distortion recordings at the substrate during the fabrication of 50- and 100-layers wall. The efficient model successfully captures the thermo-mechanical response of the sample. It also correctly predicts the effect of the number of layers on the accumulation of distortion during and after the material deposition.

The purpose of this paper is to present a new 3D printing method called Selective Laser Baking (SLB) to fabricate 3D parts with Poly Vinyl Chloride (PVC) material. The Mid Power Lasers are used at the SLB method for heating and shaping to PVC layers by laser scanning on the surface of the PVC compound. After designing a 3d model on the computer, transforming it into two-dimensional(2D) layers on common software, and controlling the laser scanning system by a computer, the pattern of each layer is constructed on the surface of PVC compound and layers are sequentially built on each other until a 3D part is made from PVC material. The most common method for producing PVC parts is molding. Fabrication of Customized PVC parts is always a challenge. 3D printing can be used to overcome this drawback. Despite the existence of a simple material extrusion 3D printing technique, this technique does not provide acceptable resolution and lead time.

We present the design, fabrication, and characterization cycle of a diffractive optical element based layout, used for 1-to-7 power splitting of a Gaussian beam emitted by a single-mode fiber. First, a modified version of our earlier demonstrated mode conversion up-taper structure is designed, fabricated, and characterized, increasing the mode-field diameter of the fundamental mode by a factor of 2. Then, a newly designed diffractive optical element is optimized to convert the expanded field distribution to a seven Gaussian-spot hexagonal array with 45 μm spacing, at an optimal propagation distance of only 61 μm, achieving splitting in a non-paraxial diffraction regime. The two components are combined into a monolithic design encompassing both adiabatic field expansion and efficient phase modulation in a single, highly miniaturized component. The power splitter is fabricated directly on the cleaved facet of a single-mode fiber, in a single step, using direct laser writing based on twophoton polymerization. The small spatial extent of the power splitter allows for a highly compact, integrated solution for wide-angle, fan-out power splitting of a Gaussian beam in single-mode interconnect and sensing applications.

This article presents the experimental investigation of the ability of a novel technique called Selective Laser Baking(SLB) to fabricate 3D printed micro-optics with Polydimethylsiloxane (PDMS), which has numerous applications due to its characteristics. SLB is a direct writing laser method that uses the thermal effect of a laser beam to fabricate 3D parts. In this method, absorption of the laser heats the emitted locations; increasing the temperature accelerates the hardening procedure and causes the PDMS mixture to get hard immediately. This fabrication technique is a unique method that contributes to fabricating 3D print with two-based thermoset polymers. In addition to analyzing the laser beam heat transfer in PDMS with COMSOL Multiphysics, multiple two and three-dimensional experiments were performed to investigate the optimal printing parameters. Experimental results have shown the ability of the SLB 3D printing method to fabricate microstructures such as micro-optics and microfluidics.

The additive manufacture of polymer optical elements has the promise of reducing component weight, providing new design capabilities, and enhanced performance for a wide variety of military and commercial optical systems. This paper reviews progress in the development of 3d printed Gradient Index (GRIN) lenses and optical phase masks. The 3d printing process uses a modified commercial inkjet printer and UV curable polymers that have specific nanoparticles added to them to modulate the index of refraction. Complex optical phase masks for the generation of Airy laser beams and polymer GRIN lenses to replace conventional glass lenses used in a telescope or riflescope are created. The generation and propagation of Airy beams using these polymers generated optical phase masks has been investigated and analyzed through experimentation, simulations, and comparison with recent theoretical predictions. Airy beams have been generated using the conventional approach using a spatial light modulator and compared to the 3d printed optical phase masks. The maximum non-diffracting propagation distance of an aperture truncated Airy beam was experimentally measured. The results show that the maximum non-diffracting propagation distance of a laboratory generated Airy beam is proportional to x₀² , the Airy beam waist size squared. The size of the Gaussian envelope beam has a weaker effect on the Airy beam propagation distance. The experimental results were compared with current theoretical models. A set of 1 inch diameter 100 mm focal length polymer GRIN lenses have been made using 3d printing. Transmission and modulation transfer function (MTF) results for the lenses are reported.

Photolithography has become a powerful tool in the fabrication of micro-optical elements following the advancements in grayscale approaches. However, hitting tight design tolerance goals require precise control of all parameters such as temperature, resist nonlinearity or preventing vignetting. In this work we took an alternative route to these problems by combining maskless lithography with digital holography. Addition of digital holography enables the use of feedback by measuring the quantitative phase of specimen near real time and in situ nondestructively. After each near UV exposure, phase retardation map of exposed photopolymer is measured with digital holography part of the system. Any deviation from target phase is corrected by changing the pattern displayed on the mask. We showed that the proposed method reduces the standard deviation of resulting phase compared to traditional one-shot grayscale lithography. It also does not require any precalibration of photoresist and relaxes the constraints for uniform UV illumination in sample plane.

Scaling up from prototype to high volume manufacturing is a challenge for many technologies. In particular for waferlevel manufacturing of advanced freeform micro-optics, there is a gap which needs to be addressed. The combination of two-photon grayscale lithography (2GL), step and repeat nanoimprint lithography (S&R NIL) followed by SmartNIL® replication enables to expand design freedom while still being able to scale up from prototype to high volume manufacturing. This entire process flow was used to pattern microstructures with challenging freeform geometries which are required for emerging devices and applications across the photonics market. Additionally, to further increase the flexibility and performance of the devices, it is possible to use advanced high refractive index materials, which, so far, have been limited to applications in sub-micrometer thin layers, for freeform micro-optics and micro lens arrays. The results presented in this work provide an overview of the versatility and recent achievements of NIL in terms of structure sizes and shapes using different imprint resins to obtain even more design flexibility for freeform micro-optics and micro lens arrays.