This PDF file contains the front matter associated with SPIE Proceedings Volume 12103, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

The Panoramic Annular Lens (PAL) form provides a hyper-hemispheric field of view in a monolithic element. The lens uses two refractive and two or more internally reflective surfaces to create an afocal or near-afocal imaging system. The resulting field of view loses some coverage off of the central axis due to obscurations from the multiple surfaces, resulting in a doughnut-like image. The PAL form provides significant size and complexity advantages over fish-eye and other wide-angle lenses, as multiple individual elements are combined into the single block monolith. The design form also provides ideal locations for mounting and blocking based on the intersection of the various curves into the surface. Up to this point, PAL designs have been limited to small spectral regions based on the substrate material. We developed several visible through long-wave variants of this form in a variety of multiple multi-spectral materials, each providing an annular coverage from 30-110° off of the central axis. Results are shown from a fabricated prototype in water-clear Zinc Sulfide, including imaging tests in the visible and LWIR.

Compact, high resolution and wide-angle infrared imaging systems are the paragons for security and situational awareness applications. Coherent fiber bundles (CFB) provide a platform to relay curved images, formed by optical systems such as a monocentric lens, to flat focal plane arrays so that image flattening is decoupled from image formation. This enables hundredfold increase in resolution per unit volume for wide angle lenses. We present hybrid chalcogenide/polymer CFB for mid-wave infrared (MWIR) image relay. We design the lens system and the AR coating for the bundle, and finally demonstrate a stack-and-draw process to yield 10μm pitch CFBs with about 8,000 cores.

We present the design of a “hole” meta-atom basis, the inverse of nanorods, in the silicon-on-insulator (SOI) platform with a zinc sulfide (ZnS) anti-reflection (AR) layer that gives an average transmittance of 92% across half of the midwave infrared (MWIR) band from 3.5 to 4.5 μm. We numerically show this hole meta-atom exhibits reduced phase dispersion across the MWIR compared to the archetypal rod geometry. Effective index modelling is shown to accurately describe propagation phase delay through hole meta-atom periodic array. Bloch eigenmode analysis further reveals the small phase dispersion originates from its small modal index dispersion. A simple, analytical effective index model that only involves geometric and material parameters such as array filling factor and material refractive index is demonstrated. We further use this hole meta-atom to design a pair of metasurfaces to correct optical aberrations from a conventional lens and show that the performance is superior to its rod counterpart due to the reduced phase dispersion.

PLX was founded in 1955 as Precision Lapping and Optical Company, producing highly accurate optical domes, lenses, prisms, and mirrors. In the 1970’s the invention of the hollow retroreflector by PLX enabled work on mission-critical projects for military and space applications. PLX’s proprietary technologies and manufacturing capabilities with high-performance optical systems are renowned for performing under the harshest environmental conditions such as extreme temperature, combat and deep space while maintaining near-perfect accuracy over time. In 2000 PLX invented the Monolithic Optical Structure Technology™ (M.O.S.T.) [1]. M.O.S.T is a unique optical innovation that combines all the elements of a complex optical design into a single monolithic unit - creating superb optical and thermal stability as well as unsurpassed shock and vibration resistance. Today, PLX continues to push the boundaries of boresighting and targeting. With their exceptional stability, PLX’s boresighting systems have been repeatedly proven in the field. This paper will expand upon the M.O.S.T. solution with case studies of M.O.S.T. designs and results for specific applications, such as laser delay line systems, boresighting, and telescope alignment systems. Other applications can utilize this novel technology, such as spectroscopy, interferometry, LIDAR, free space optics, laser tracking, laser cavities, satellites, boresighting, laser beam steering systems, alignment, or sensors.

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 polymer 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 x0 2 , 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 is reported.

3D printing is a rapid manufacturing methodology which provides low turnaround times greatly advancing the efficacy of low technology readiness level (TRL) prototyping of opto-electric sensors. Herein, we describe the design and evaluation of a discrete adjustable optical prototyping system, refered to as the Rapid Indexable Positioning System which can be utilized in conjunction with formfitting 3D printed opto-mechanical components to aid in the development of aerospace payloads. “Grid holes” are integrated to an enclosure wall using a grid pattern of holes on every face of a payload enclosure. This works in conjunction with various components that can be semi-permanently positioned with the use of “studs,” allowing for rapid validation of layout within an enclosure. The demonstration of this technique is conducted on prints using both PLA and ABS with the use of a Raise3D Pro2 Printer with the print properties of 20% honeycomb infill and .2mm layer height. The use of this technique in payload enclosure development facilitates rapid and indexable changes to be made, requiring that only a single enclosure, which requires nearly 24 hours to print. This print can be utilized with multiple iterations of each part to be indexed, requiring only about 1 hour. Additional Dynamic oscillation simulations can be conducted to ensure that the optical components would remain within a necessary manifold of deflection once the viability of their final location was verified.

Additive manufacturing (AM, 3D printed) enables, among other advantages, the in-house fabrication of optomechanical components with minimal tooling investment and labor hours per finished part. Currently, supply chains for high-value optomechanical components are delicate and can be a potential area of concern for scheduling; there is an advantage from using bulk sourced filament and commercial off-the-shelf (COTS) components to meet design needs. Additionally, spacebased manufacturing can incorporate AM, where a remote design engineer transmits a part file to a permanent orbiting, Lunar, or Martian platform to facilitate and optimize the use of personnel hours. Herein, we describe the design objectives, process, and test evaluation for a versatile optomechanical positioner to incorporate an optical component (emitter, mirror, beam-splitter, etc.) to a precision instrument at a fixed location honed surface normal. The designed AM optical positioner (OP) is manufactured from low off-gassing nylon 6,6. It has incorporated low-mass components such as silicon carbide (SiC) to reduce further the mass of the kinematic systems with a minimum number of secondary tensioners and actuators. This positioner provides one degree of translational freedom (infinite translation), either along the optical path or normal to it, with two degrees of angular degrees of freedom (Δα_max= 189.2 mrad and Δβ_max= 375.9 mrad) with minimal off-axis shift about the rotation center. We have verified the designs in static tests and isothermal shake table tests.

There is an increasing number of applications for rapid deployment mid-wave infrared (MWIR) and long-wave infrared (LWIR) optical systems, especially for proof-of-concept. These systems are typically placed in test environments where they need an environmental enclosure window for protection. Traditional IR windows, like Germanium and Zinc Selenide, often have high costs and long fabrication lead times, especially for custom designs. Thin, readily available polymers have potential of solving this problem where they may have high enough transmission in the IR to be of use as an inexpensive environmental enclosure window. This paper outlines 33 polymer materials that have been tested as candidates for IR windows by measuring transmission and reflection and then calculating values of refractive index and extinction ratio from the measurements. We have identified 7 polymer materials as having high enough transmission to be used as an IR window. Further testing was done to characterize wavefront error and image quality of MWIR and LWIR cameras with these polymer windows. The combined results show 3 promising materials in the MWIR and LWIR.

Chalcogenide phase change materials (PCMs) are uniquely suited for spectral tuning applications due to their contrasting dielectric material properties. Recent headway has been made towards realizing tunable photonic devices using twodimensional, sub-wavelength resonators by carefully designing geometries that optimize optical, electrical, and thermal performances using multi-physics analyses and machine learning. In this paper, we tackle two other essential aspects for creating application-specific, tunable PCM devices: (1) scalability of the device size and (2) high-throughput fabrication techniques. We employ a deep ultraviolet (DUV) stepper projection lithography to manufacture over 100 densely packed GST metasurfaces, each with a sample size of 5×7 mm², all on a 4-inch Al₂O₃ wafer. These metasurface structures were discovered using artificial neural network (ANN) techniques and confirmed by finite-difference-time domain calculations. The primary structures under investigation were nanobar configurations enabling amplitude modulation at short-wave infrared wavelengths to realize efficient optical switches for free space optical multiplexing. The DUV fabrication technique can easily be extended to other metasurface geometries to demonstrate multi-functional, non-volatile photonic devices.

Fresnel reflection losses are detrimental to performance of optical systems. Not only do reflections diminish transmission, but rebounding energy can lead to system damage and catastrophic failure in high-energy and highpower laser systems. Suppression of Fresnel reflections by conventional thin-film coatings does not suit all applications, especially high-energy laser (HEL) systems, as foreign material coating can burn off or delaminate. Sub-wavelength structured surfaces minimize reflectivity by gradual change of refractive index from ambient to substrate. Consisting of no foreign material, anti-reflective structured surfaces (ARSS) offer a viable method to suppress reflectivity. ARSS on fused silica (SiO2) windows have been previously shown to exhibit high laser-induced damage thresholds (LIDT), comparable to bulk material LIDT. This study further explores the application of ARSS on low-dispersion crown/soda-lime glass, specifically SCHOTT B270. Random anti-reflective structured surfaces (rARSS) were fabricated by reactive ion etching a surface of 1-inchdiameter, 2-mm-thick, B270 Superwhite optical windows. Transmission results taken via an Agilent CARY 60 spectrometer on single-side processed windows demonstrate greater than 95.0% and 94.5% transmission across 700- 800 and 530-1000 nm wavelength bands, respectively. A 100% enhancement of transmission from single facet in this band would theoretically result in 95.6% overall transmission. Therefore, we demonstrate transmission enhancement factor of 85% for one facet etched, as compared to untreated B270. Scanning electron microscopy (SEM) was used to analyze sub-micron surface morphology of the rARSS B270 windows. Randomly orientated “sponge-like” surface features 20-200 nm in width were observed. Successful high broadband transmission enhancement of B270 has been demonstrated using novel rARSS treatment.

Long wavelengths for 7.5-12μm and particularly above the upper limit of 12μm applies a huge challenge for LWIR (long wavelength infrared) optics. Of the known materials, sulfides and particularly selenides can work up to these wave lengths, but they are high index materials. For HL(High-Low) optical designs low index materials with low absorption remain a challenge. Fluorides have low index with bandgaps and outperforms other known LWIR materials, but absorption exists with traditional conditions at the upper limits of LWIR. Some fluorides can be better but because of the toxicity and durability their applications are restricted. In this research we successfully improved LWIR optics transmissions in wavelengths of 7.5-13.6μm and above by optimizing fluorides IAD (Ion assisted deposition) processing conditions. This study clearly shows that fluorides, for example YbF₃, there is ion energy threshold for the absorption edge above which the material absorption can be greatly reduced regardless the approach of the evaporation methods, such as e-beam or thermal evaporation. This threshold is also closely related to stress and microstructure of the coating layer, above which the layer tends to be a dense and low defect microstructure by TEM and low tensile by stress analysis. With optimized ion energy in the IAD process, LWIR optics can increase transmission by 3.5%, 2.0% and 7.5%, at wavelength of 7.5, 10.5, and 13.5μm respectively. Compared to the traditional approach, single layer absorptions at the same wavelength from the optimized IAD process drop about 3%, 6% and 14%, respectively.

Infrared cameras could serve automotive applications by delivering breakthrough perception systems for both in-cabin passengers monitoring and car surrounding. However, low-cost and high-throughput manufacturing methods are essential to sustain the growth in thermal imaging markets for automotive applications, and for other close-to-consumer applications, which have a fast growth potential. With the reduction of the pixel pitch of microbolometer detectors, their cost has decreased considerably and now the optical part represents a significant part of the system cost. Fast low cost infrared lenses suitable for microbolometers are already sold by companies like Umicore, Lightpath, FLIR… Chalcogenide glasses are widely used as materials for optics because they have many cost advantages, especially due to the possibility of mass molding the optics. However, with the reduction of the pixel pitch, it is more and more difficult to design high performance lenses with a limited number of optics. The possibility of molding the optics allows us to use many highly aspherical surfaces at affordable costs. However, Chalcogenide glasses have usually a lower refractive index than other more expensive infrared materials such as Germanium. Indeed, high refractive index materials are known to be effective in attenuating the amplitude of many geometric aberrations. In this presentation, we evaluate the interest of high index Chalcogenide lenses, especially TGG and TGS, to design optical systems meeting the needs of the automobile with a limited number of optics. TGG glass has an index of refraction of 3.396 at a wavelength of 10µm, i.e. its index of refraction is close to the Silicon one and was initially studied for space applications. TGS has a lower index of refraction (3.12@10µm) but can be used in a cost effective manufacturing process by using flash spark plasma sintering (SPS) on raw powder. Demonstrators with TGG glass have been made and their performance evaluated.

The airborne lunar spectral irradiance (air-LUSI) mission is an inter-agency partnership between the US National Aeronautics and Space Administration and the US National Institute of Standards and Technology. Air-LUSI aims to make SI-traceable measurements of lunar spectral irradiance at visible to near-infrared wavelengths with unprecedented accuracy. To minimize uncertainty, lunar spectra are acquired above 90 % of the Earth’s atmosphere aboard NASA’s Earth Resources aircraft, a civilian descendant of the U-2 spy plane. The data collected by the air-LUSI instrument is poised to improve upon current lunar calibrations of Earth observing satellites. The air-LUSI team recently completed their Operational Flight Campaign in Palmdale, California in March 2022. In addition to the Engineering Flight Campaign of August 2018 and the Demonstration Flight Campaign of November 2019, the air-LUSI instrument has been successfully deployed on over ten lunar spectral measurement flights at altitudes of roughly 21 km. This paper presents the simplified double gimbal design that was capable of recently tracking the Moon with a root mean square tracking error of less than 0.1°.

METimage is the Visible/Infrared Imaging mission (VII) on METOP-SG series, providing moderate resolution optical imaging of atmosphere and surface variables in multiple spectral channels ranging from 0.443 to 13.345 µm with a spatial sampling of 500 m. The instrument was developed by an industrial team led by Airbus Defense and Space GmbH on behalf of the German Space Administration Deutsches Zentrum für Luft und Raumfahrt (DLR) with funds from the German Federal Ministry of Transport and Digital Infrastructure and co-funded by EUMETSAT under DLR Contract No. 50EW1521. Hensoldt Optronics GmbH designed and manufactured two main components for the METimage instrument: the hyperspectral filter assemblies and the refractive relay infrared optics. The components are challenged by harsh environmental loads, while maximum optical performance must be met for precise data collection. Optics mounting was realized by sophisticated glue-free design, which had to be tested for long term sturdiness, stability and optical performance at cryo-vacuum conditions. Therefore, a well-tailored assembly and testing procedure was developed, based on an Optical Ground Support Equipment (OGSE) capable of illuminating and sensing wavefront errors at multiple MWIR and LWIR wavelength. After 6 years of development the project comes to an end and at the beginning of 2022 all flight models are delivered. Hensoldt Optronics GmbH shares in this paper insights into the testing strategies and setups for the relay optics. The design and functionality of the used OGSE is explained as also the importance of the accompanying optical modelling.

The performance of modern optical systems is dominantly determined by the precision of the alignment of single lens elements in the optical path of the system. The highest alignment precision as well as leading productivity in fabrication can be achieved by alignment turning. A lens to be assembled is glued into a metal mount not considering precision orientation yet. The lens and mount are introduced to an alignment turning machine to measure the optical axis and to correct the metal mount by slow tool turning in a way that the optical and mechanical axis have the same orientation after machining. Remaining shifts of down to 1 micron and tilts < 10 arcsec can be achieved within minutes. As the glue has been solidified prior to machining, there are no more subsequent displacements. The new machine system to be presented is the world leading platform for flexible alignment turning of various types of optics. With its recent developments, it is capable of measuring IR optics with a 4.05 μm laser system. In addition, the optical axis of aspherical lenses can be measured by a full aperture confocal scan without any spherical approximation. Full automation applies to the measuring steps, the slow tool machine program calculation as well as subsequent quality assurance steps. Current tests on objectives with aspheric lenses have led to an overall optical system improvement of < 30% at significantly reduced assembly times. The presentation covers an introduction to the technology and the machines as well as sample machining results.

Optical properties of ULE® 7973 were assessed by using spectrophotometers and variable angle spectroscopic ellipsometer, indicating that ULE® 7973 is highly transmissive beyond the visible. The transparency is terminated by two fundamental absorption edges in the UV and middle-wave IR (MWIR). The UV and MWIR absorption edges are dominated by the titania and the silica constituents, respectively. We associated UV cut-off wavelength with optical bandgap and derived the optical dispersion by modeling both the spectral transmission and the ellipsometric data. The exponential absorption tail, the Urbach energy, in the UV increases linearly with temperature ranging from room temperature to 650 °C, whereas the optical bandgap decreases linearly over the same temperature range. Temperaturedependent coefficient is 18 μeV/°C for the Urbach energy, and - 0.7 meV/°C for the optical bandgap. The results indicate that the ULE® 7973 is a thermally stable refractive optical glass which maintains a broad spectral transparency even at elevated temperatures.