This PDF file contains the front matter associated with SPIE Proceedings Volume 11403, including the Title page, Copyright information and Table of Contents

Los Alamos National Laboratory has been involved in advanced remote sensing since its inception in 1943. From detecting gamma ray bursts in space, generating real time geo-rectified imagery in Iraq or zapping rocks on mars, Los Alamos has developed numerous advanced sensing and imaging systems for a myriad of missions. However, getting the data is often the easy part of the problem. How we collect, manage and process large disparate data sets, maintain end-to-end data integrity and generate low latency, actionable knowledge with minimal human oversight is generally the bigger part of the puzzle. So do we have a crystal ball for the future? By looking at how these various technology areas have been developing and how they are being used in conjunction with one another, we can start to understand what technology gaps exist and just what might be possible in the future.

Optical metasurfaces consist of nanostructured meta-atom arrays that allow on-demand manipulation of the phase, amplitude and polarization of light. The promise of metasurface optics lies in the arbitrary wavefront control with an optically-thin, flat/conformal form factor and subwavelength-arrayed device architecture, in drastic contrast to traditional bulk optics. In this talk, we’ll discuss opportunities and challenges of using metasurfaces in imaging systems. We further present novel imaging optics and architectures enabled by ultra-thin, all-dielectric metasurfaces, such as ultra-wide field-of-view and reconfigurable meta-optics with unprecedented optical performance. We show that the judicially-engineered meta-optics can significantly boost the imaging performance, allow new functionalities and effectively reduce the size, weight, power and cost (SWaP-C) of future optical systems.

Many fixed focus lenses for uncooled state of the art LWIR cameras are frequently factory set at large distance and therefore produce blurred thermal imagery when targets are closer than 80 m. To solve this issue, we propose a freeform based varifocal attachment that consists of two thin Germanium plates and is derived from Alvarez-Lohmann concept. When implemented together with our low-cost f/1.1 65 mm LWIR lens, the varifocal attachment enables sharp thermal imagery from 2 m to infinity. Extensive tolerancing study supports feasibility of this freeform device for future manufacturing.

NRL is developing new glasses that transmit within the visible to LWIR range for use in multispectral imaging. We had previously developed NRL glasses which transmit in 0.9 to > 12 µm in wavelength, with refractive index ranging from 2.38 to 3.17, to expand the glass map and provide compact solutions to multispectral imaging systems. These glasses were specifically designed to have comparable glass molding temperatures and thermal properties so that they can be laminated and co-molded into optics with reduced number of air-glass interfaces (lower Fresnel reflection losses). These NRL glasses also have negative or very low dn/dT, making it easier to athermalize the optical system. A set of NRL glasses can be diffused to make infrared graded index (IR-GRIN) optics. Our multispectral optics designs using these new materials demonstrate reduced size, complexity and improved performance. The glass database compatible with Zemax and CodeV is available for distribution. We are adding n

The last twenty years have seen a dramatic improvement in the performance of infrared detectors, especially those with uncooled microbolometer arrays. These make new commercial applications possible, from the Internet of things to drones for crop monitoring. Such emerging markets are constantly pushing the requirements on the existing technology to improve cost, performance, weight and size. In this context, gradient index (GRIN) lenses can offer a new degree of freedom compared to their homogeneous counterparts. For example, recent papers have shown how GRIN lenses could help reduce the number of elements in a system, by helping correct lens chromatism and athermalization. While the interest in using GRIN is obvious, mastering their fabrication with infrared materials remains highly challenging. Encouraging progress has been made in that direction, for instance by stacking different materials or by laser writing. Very recently, it has been demonstrated that partial crystallization of chalcogenide glass allows for tuning the refractive index. In this paper, we introduce a new technique based on the controlled formation of nano-crystallites in chalcogenide glass to fabricate the first macroscopic radial GRIN in the infrared. We also propose a simple way to test the index gradient value by interferometry and demonstrate GRIN with index contrast of ▵n ~ 3⋅10^-2 between the center and the edge of the disk. The process is easily repeated and opens the possibility for a rapid transfer to the industry.

Rugged optics and window materials with good visible and IR transmission are needed for several sensing and imaging application. Some of the applications require very thick windows or windows in complex geometries, which impose additional limitations on material selection. Magnesium aluminate spinel (MgAl2O4), or spinel for short, is a rugged window material with excellent transmission in ultraviolet to midwave infrared (0.18 – 5.5 m) wavelengths. Spinel is comparable to sapphire and ALON in its ruggedness while having superior transmission near 5 m in wavelength. With its cubic crystal structure, spinel is isotropic unlike sapphire which is birefringent. We have been developing high optical quality spinel ceramics in different shapes and sizes. Current status of these efforts in making spinel windows in large sizes and conformal shapes for several imaging applications will be discussed.

II-VI Aerospace & Defense currently supports the defense industry on several aerospace platforms by providing high quality, large, single crystal sapphire substrates and windows. There continues to be a rapidly increasing interest in large substrates capable of use in high energy laser (HEL) systems. Such applications require materials with high thermal conductivity and high thermal shock resistance, high strength, and near-zero defect levels. Laser damage-inducing defects include those which are incorporated in the substrate during crystal growth, as well as defects incurred during routine optical fabrication and finishing processes. In the following paper, II-VI A&D presents data for a-plane and cplane sapphire windows of sufficient size for projected HEL applications exhibiting laser-grade surface quality and surface roughness, while still maintaining low rms transmitted wavefront error. Included is a discussion evaluating the benefits of sapphire for envisioned HEL windows, as well as engineering challenges that should be considered.

Brimstone Holding, a partner of Semper Fi Systems, is the first company to synthesize sulfur-based polymers with infrared transmission at a wavelength from ~700 to 6200 nm that lack chemical groups absorbing in the near-IR region. This range can be extended or narrowed if needed by using different monomers and oligomers and by variation of elemental sulfur content. In addition, this material shows possible utility as an optical adhesive as it strongly attaches to everything except silicone. Our proprietary polymer material can be produced sustainably and inexpensively in large scale without requiring the use of rare and expensive semiconductor crystals or highly toxic chalcogenide glass manufacturing. The Brimstone Lens™ material can be molded with ease into complex shapes, curvatures and sizes and is amenable to grinding and polishing. The Brimstone Lens™ polymer can serve as a base for complex IR nanostructures with previously unattainable properties. Our low cost Brimstone Lens™ will allow for numerous inexpensive applications in security and guidance systems, quality analyzers, infrared cameras, night vision goggles and optics, automotive safety, as well as in the production of solar panels and electric battery cells, along with numerous other potential uses, without diminishing the quality of an IR solution. The replacement of Germanium would minimize US dependency on China’s mining and distribution of these expensive and rare metals.

There is a need for robust optical materials with very low reflectivity and high transmission in the visible and infrared wavelength regions for use with high energy lasers. High power continuous-wave (CW) and high pulse energy laser optical systems can suffer damage from untreated optics due to undesirable Fresnel reflections. Sub-wavelength antireflective structured surfaces (ARSS) have been shown to have a higher laser-induced damage threshold than traditional AR coatings, which are necessary for high energy (multi-kW) laser components. Previous optimization of the etching process for ARSS on fused silica, among other optical materials, has yielded controlled and repeatable parameters, resultant from formation of varying depth and density profiles by randomly removing material from the surface. The “grass-like” boundaries result in gradient-index functionalities for incident optical beams, which simultaneously reduces reflection and increases transmission of the substrate. In this study, we investigate resultant optical properties of B270 Superwhite substrates, whose surfaces are modified using reactive ion etching, in order to enhance broadband transmission and lower reflectivity, thus increasing their utility for visible and near-infrared wavelength regions. We report results for ARSS fabricated directly onto the surface of 1” diameter, B270 Superwhite optical windows. Initial trials yielded single-side random ARSS (rARSS) treated samples with transmission enhancement of up to 3% from 400-1800 nm, nearing that of rARSS enhancement of fused silica, with maximum enhancement 80% that of the theoretical value between 700-900 nm.