Edward C. Kinzel

Digital Glass Forming (DGF) is a new manufacturing process for low-batch glass fabrication. The work zone temperature in DGF processes must be maintained in the glass’s working range to ensure good fabrication. If the temperature is too low, the filament will not wet to the substrate or previously deposited material and, if the temperature is too high, the filament may disengage from the substrate or previously deposited material, or it may partially vaporize. In this work, a real-time temperature control system capable of synchronizing process parameter, thermal camera, and visual camera data for the DGF process is introduced. A process parameter map for a scan velocity of 0.5 mm/s is constructed, as is a data-driven dynamic temperature process model. A digital controller is designed to regulate the work zone temperature. The temperature controller is a closed loop tracking controller that adjusts the commanded laser power to regulate the measured temperature. Two sets of experiments are conducted to analyze the controller performance. In the first set of experiments, single tracks on a substrate are fabricated with constant laser power and with the closed loop temperature controller. It is seen that the closed loop controller is able to extend the process parameter map into regions where using a constant laser power will result in a failed build. In the second set of experiments, walls are fabricated. Using constant laser power results in a failed build (i.e., material vaporization at the corners and the filament prematurely detaching from the substrate) as the temperature process dynamics change with layer and at the corners. The closed loop controller successfully fabricated the wall without vaporization at the corners and premature filament detachment as the controller adjusts the laser power to account for the changing temperature process dynamics.

We are developing circular-polarization-sensitive infrared detectors called spiral thermoelectrically coupled nanoantennas (TECNAs) for solar imaging and terrestrial sensing applications. In a spiral TECNA, a nanoscale thermocouple is used to measure the localized joule heating caused by induced currents within a spiral nanoantenna structure. This paper discusses the response of spiral TECNAs to elliptical polarization, which must be considered when performing circular polarization measurements of sources of arbitrary polarization. Measurements and simulations show that spiral TECNAs respond maximally to a specific matching elliptical polarization and minimally to the orthogonal, nonmatching elliptical polarization. Given that any polarization can be decomposed into these two basis polarizations, we find that the spiral-TECNA response to an arbitrary polarization scales with the matching-elliptical-polarization component. The spiral TECNA polarization response is analogous to that of RF spiral antennas, despite the intermediate transduction between high-frequency currents and heat.

This work studies the surface morphology and roughness differences of Si surfaces etched by XeF2 under pulsed and continuous flow conditions. During pulsed etch, XeF2 is introduced into the processing chamber in discrete doses. The sample is exposed to the fixed supply of etchant for a set duration. In contrast, during a continuous flow etch, a steady supply of XeF2 gas maintains a stable etchant concentration in the process chamber. Comparable etch rates and etch depths were attained while ensuring that both pulsed and continuous flow etching were conducted under similar chamber pressures and loading. Although the overall root-mean-square (RMS) roughness values for the continuous and pulsed etch were similar, 0.134 and 0.135 μm, respectively, significant differences in the surface morphology were observed. Laser scanning confocal microscopy, SEM imaging, and FIB cross sections of the etched surfaces revealed pronounced differences in the spatial frequency components of the surface textures. Continuous flow etching produced surfaces with sharper features and higher spatial frequency components. These results indicate that the etching methodology influences Si surface characteristics even when etch depths and rates remain constant.

The mid- and long-wave infrared regimes (5 µm to 12 µm) are important for commercial and defense applications such as autonomous vehicles, target tracking, and surveillance. While state-of-the-art photovoltaic detectors (MCTs, QWIPs, and T2SLs) offer excellent sensitivity, they require costly cryogenic cooling. Microbolometers provide affordable sensitivity but at slower speeds. Both approaches rely on IR light intensity and often lose key information like polarization and wavelength. Thermoelectrically coupled nanoantennas (TECNAs) offer a solution by utilizing nanoantennas for resonant IR absorption, providing polarization, wavelength, and directional selectivity without cryogenic cooling. TECNAs with log-spiral antennas were developed for linear and circular polarization sensing, showing enhanced performance by removing convective cooling. The devices exhibit a temporal response in the tens of kilohertz range under atmospheric and low-pressure conditions.

Multispectral sensor design for substance differentiation has traditionally relied on heuristic selection of spectral bands, often leading to suboptimal performance. Our work introduces a structured computational framework for optimizing spectral sensor designs through systematic evaluation of differentiability across a large set of candidate configurations. The framework employs a simulated computational search to explore sensor response functions and identify configurations that maximize spectral differentiation. We apply this framework to evaluate sensor designs using Gaussian-based response functions, demonstrating its ability to identify optimal sensor configurations under these conditions. While the specific results depend on the Gaussian approximation, the method establishes a functional pipeline for sensor optimization. Comparisons between different sensor configurations show that well-chosen spectral response functions improve differentiation, while suboptimal selections lead to overlapping responses and reduced classification accuracy. Additionally, we analyze different scoring strategies, showing that prioritizing worst-case separability favors uniformly spaced response functions, whereas group-based separation leads to designs optimized for distinguishing between predefined substance categories. We also perform a structural analysis of top-ranked designs, revealing that many high-performing configurations share similar patterns. This suggests that strong differentiation can often be achieved through a small number of representative sensor architectures. These findings highlight the importance of a systematic approach to sensor design, enabling comprehensive evaluation of sensor configurations without relying on manual selection or trialand-error methods. While this study employs an exhaustive grid search, the framework is adaptable and can incorporate machine learning-based optimization techniques, such as genetic algorithms or reinforcement learning, to refine sensor selection. This work establishes a scalable framework for optimizing spectral differentiability, with applications in material classification, chemical detection, and security screening.

This study validates a fiber optics-based surface enhanced Raman spectroscopy (SERS) sensor for detecting Salmonella in raw turkey samples. The sensor uses nanoantenna arrays on a side-polished optical fiber core with a fixed periodicity of 0.77 μm to maximize the SERS signal intensity. A 3D-printed chamber and microstructure optimize light reflection, improving sensitivity. The sensor detects Salmonella at 0.4-0.5 CFU/ml in 10 minutes, offering cost-effective, portable pathogen detection.

Selective Laser-Induced Etching (SLE) is a micromachining technique specifically applied to transparent materials like various glasses, involving laser irradiation to locally modify the material followed by wet chemical etching for selective material removal. We adapt the SLE method to optimize femtosecond laser patterning of fused silica molds for casting polymer-based high aspect ratio microcavities with enhanced light absorption properties. Surface reflow via CO2 laser polishing addresses issues of surface roughness and polymer adhesion, impacting surface smoothness and reflectance. Our findings demonstrate SLE's potential for efficient fabrication of intricate microstructures for applications of flexible, dark surfaces.

The low CTE, high temperature and strength of glass are appealing for structural applications in optical assemblies. We investigate depositing primitive cubic lattices using coordinated 4-axis motion using a CO₂ laser to spot fuse filaments.

We present thermoelectrically coupled nanoantennas (TECNAs) with log-spiral antennas for mid- and long-wave infrared detection. The nanoantenna resonantly absorbs the incident IR radiation and, due to its shape, provides selectivity for circular polarization. We used HFSS simulations to design TECNAs with both left- and right-handed antennas and show the effect of each design parameter of the spiral on the response of the devices. The fabricated devices were characterized at 10.6 μm wavelength, and the measurement results show that the response is about five times larger when the polarization handedness of the incident IR radiation matches to the antenna