This PDF file contains the front matter associated with SPIE Proceedings Volume 10627, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Using a novel computational imaging architecture, we double the field of view of a long-wave infrared microbolometer camera while maintaining resolution. Due to the compact designs enabled by this architecture and the critical impact of resolution on classification performance, this approach is compelling for surveillance applications where low size, weight, power and cost (SWaP-C) systems are desired. We detail the optical design, characterization, and performance of a compact, refractive, optically multiplexed imaging system for use in the long-wave infrared (8-12 μm). A pair of prisms are used to divide the aperture and expose the uncooled microbolometer focal plane to two fields of view simultaneously, doubling the number of output pixels and the horizontal field of view. The image is reconstructed by rotating the prisms about the optical axis, inducing opposing vertical shifts in the two channels. Focal length, field of view, MTF, and NEDT are used to compare performance to a conventional camera. Shifting methods for proper demultiplexing are discussed, and reconstructed images are offered as a demonstration of system performance.

Single aperture multispectral systems are becoming prevalent thanks to advances in multispectral detectors, new optical materials, and new methods for selecting materials that minimize chromatic and thermal focal shift. This design study focuses on design of a three field-of-view, multispectral lens operating across the MWIR and LWIR spectral regions. The lens in question will have an f-number of f/3 with a 3X zoom ratio. The narrow full field-ofview of the lens is 3.33° with a wide full field-of view of 9.99°, the length of the system is 163 mm. The performance goal for the lens is diffraction limited over the thermal region. The study will provide an overview of material selection using an updated γv-v diagram, to provide achromatic and athermal characteristics. The study will then step through first order layout, optimization with key constraints, and tolerancing for manufacturability. Finally, the study will provide detailed analysis of system performance including as-built MTF over temperature, aberration analysis, and NETD contributions from narcissus.

Over recent years, the pixel size of uncooled thermal detectors has kept shrinking, going from 50 μm in the last decade to 17 μm today. The latest generation of detectors, with 12 μm pixel pitch and smaller, come with a new set of challenges. In this paper, we investigate the link between pixel size and optics cost and performance by relying on a well-defined framework and concrete examples. First, we briefly clarify the relationship between the reduction in pixel size and requirements on the optics, from both the radiometric and the resolution point of view. Within this framework, we study the effect of decenter corresponding to current state-of-the art manufacturing on performance and price of lenses. Finally we demonstrate that reducing the pixel size indirectly leads to much more demanding lenses. As the new generation of 12 μm pixel pitch arrays are emerging in the long wave infrared, lenses will become more complex and harder to manufacture. Consequently, optics with equivalent levels of performance can become more expensive.

Additive manufacturing (AM) is a rapidly advancing area in which new mechanical design techniques can be used to greatly benefit optical sensor designs. Emerging technologies now allow us to utilize many different materials to print three-dimensional structures in complex, accurate shapes. This enables designers to build volumes with optimal material distributions, allowing them to tailor a structure’s response to temperature or vibration. Introduction of these methods provides an excellent opportunity for a designer of optical sensors to make significant for harsh and varied environments. The Army is currently funding research of a Robust Seeker Optomechanics project to design novel mechanical structures promising to athermalize and vibration-isolate a missile seeker’s imaging components. The structures would eliminate the need for moving parts or expensive components such as gimbals or complex lenses. Methods for topology optimization allow a computer algorithm to fill the volume around a missile seeker lens and camera focal plane with a uniquely shaped composite material. These uniquely constructed spaces can both move or maintain the position of the imaging components when the missile experiences large temperature variations and vibrations thus improving performance. Army Aviation and Missile Research and Development Center (AMRDEC) lens designers teamed with Materials Sciences Corporation (MSC) to develop topology optimization algorithms based on frequency tailoring of structures specific to another project underway. The initial phase of this effort is to demonstrate mechanical athermalization of a simple long-wave infrared camera in a small, 2.75-inch-diameter missile seeker configuration. MSC created a series of volume optimizations and algorithm refinements to study the solution space for a 45mm, F/1.4, 14-degree lens and a FLIR Quark2 640 sensor between -35°C and +50°C. The example problem provides a relevant, achievable athermalization goal as well as an opportunity to include vibration damping in later phases. The results of initial volume optimization reveal that one can achieve a buildable athermalized design by separating the detector mount structure from the lens retention structures. The study also showed that mechanical and optical design need to be coupled into a common optimization solution to achieve the best results. MSC measured the mechanical properties of many additivelyproduced metals and plastics to use in the optimization. The team produced a lens in a prototype housing, and will measure it for thermal stability soon after this paper is submitted.

There is a strong desire to reduce size and weight of single and multiband IR imaging systems in ISR operations on hand-held, helmet mounted or airborne platforms. NRL is developing new IR glasses that transmit from 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 new NRL glasses also have negative or very low dn/dT, making it easier to athermalize the optical system. Our multispectral optics designs using these new materials demonstrate reduced size, complexity and improved performance. The glass database is now available for distribution. Some of the NRL glasses are also available commercially. This presentation will cover discussions on the new optical materials, multispectral designs, as well fabrication and characterization of new optics.

A compact zoom system originating from a generalized form of the Alvarez-Lohmann (AL) varifocal lens concept is developed and discussed here in terms of its potential future applications in infrared imagers. Design methodology based on the use of different polynomial representations of corresponding freeform surfaces is also briefly outlined. In particular, a targeted polynomial technique, which can reduce the dimensionality of the optimization task, is put forward. Silicon-based AL zoom solution is found especially attractive: it can work in both in MWIR band and quasimonochromatic SWIR channel. Complex freeform surfaces can be generated in Silicon substrates by using dedicated SPDT processes. As a design example, a 3x MWIR/SWIR afocal Galilean freeform zoom is presented which covers a FOV range from 7.4° to 22.5° and offers close to diffraction limited performance.

Duo-lateral effect detectors provide a continuous analog output proportional to the displacement of the centroid of a light spot from the center, on their active area. In this study, first of all the information about lateral effect detectors, some basic concepts about utilisation of the duo-lateral detectors, lenses have given and the mechanical parts which are necessary for making optical design verification tests of this system has been introduced. Then, experimental results have compared with theoretical results.

Long Wave Infrared (LWIR) lenses require performance over a wide wavelength range of 7-14 μacceptance and efficient transmission. The subwavelength structures in the lens designs should conform with the capabilities of the current state of the art Deep Reactive Ion Etching (DRIE). The result of etching high aspect ratio 78:1 features in silicon is presented. The subwavelength structures are model using Finite-Difference Time-Domain (FDTD) simulation and a region of strong positive dispersion has been identified. By using the strong positive dispersion with periodic index steps, an achromatic focusing surface can be fabricated in a single etch step. Using custom modeling software, the propagation of light in the range 7-13 μm is performed on the achromatic surfaces. The surfaces have a very efficiency based on the results from the (FDTD) simulation. The design and performance of chromatic lenses are presented. The lenses enable interesting imaging designs for LWIR imaging applications. Results of testing the achromatic properties of silicon structures is presented.

Novel optical materials capable of advanced functionality in the infrared will enable optical designs that can offer lightweight or small footprint solutions in both planar and bulk optical systems. UCF’s Glass Processing and Characterization Laboratory (GPCL) with our collaborators have been evaluating compositional design and processing protocols for both bulk and film strategies employing multi-component chalcogenide glasses (ChGs). These materials can be processed with broad compositional flexibility that allows tailoring of their transmission window, physical and optical properties, which allows them to be engineered for compatibility with other homogeneous amorphous or crystalline optical components. This paper reviews progress in forming ChG-based GRIN materials from diverse processing methodologies, including solution-derived ChG layers, poled ChGs with gradient compositional and surface reactivity behavior, nanocomposite bulk ChGs and glass ceramics, and meta-lens structures realized through multiphoton lithography (MPL).

Custom formulated nanolayered Gradient-Index (LGRIN) polymeric optical materials offer capabilities not possible in conventional GRIN or monolithic optics. Large scale processing of nanolayered polymer films with custom refractive indices has enabled production of polymer GRIN lenses with arbitrary spherical refractive index distribution in optics ranging from 6 to 90 mm diameters. Utilizing this nanolayered polymer film material a design and fabrication case study was performed to compare the performance of a LGRIN achromatic singlet to a traditional commercial glass lens achromatic doublet. High performance LGRIN achromatic singlet lenses were designed with non-linear, spherical refractive index distributions using specially developed ZEMAX design tools and fabricated. The performance of an f/5 LGRIN Achromatic Singlet is compared to a high-quality commercial glass f/5 Achromatic Doublet. Optical performance of LGRIN optics was shown to significantly reduce optical system mass, volume, and optical element count as compared to a commercial glass achromatic doublet while simultaneously improving performance. The LGRIN lens exhibits significantly smaller on-axis RMS spot radius of 2.8μ, compared to the glass doublet 3.5μ, with similar reduction off-axis as well, higher MTF, and better color correction while lowering total optic weight from 9.84g for the glass doublet to 3.80g in the same volume for LGRIN. LGRIN achromatic singlet fabrication and metrology is discussed within an accompanying manufacturing methodology overview of the LGRIN lens fabrication process. Additional information on the technology manufacturing/design space will be presented as a bridge toward SWaP advantages for incorporating the technology into more robust Vis-NIR optical systems and devices.

Gradient index (GRIN) lenses have been created for imaging in the infrared regime by diffusion of chalcogenide glasses. The GRIN lenses are shaped using a combination of precision glass molding and single point diamond turning. The precision glass molding step, is known to cause a drop in the index of refraction in both oxide and chalcogenide glasses. This drop is a direct result of the cooling rate during the molding process. Since the GRIN lenses have an index of refraction profile created by diffusion of multiple chalcogenide glasses, we would expect that the index drop would vary as a function of position. In this paper we investigate the expected profile change due to the index drop of the constituent chalcogenide glasses, as well as report performance data on the GRIN lenses.

Graded index (GRIN) optics offer potential for both weight savings and increased performance but have until recently been limited to visible and NIR bands (wavelengths shorter than about 0.9 µm). NRL has developed glass-based IR-GRIN lenses compatible with SWIR-LWIR wavebands. Recent designs show the potential for significant SWaP reduction benefits and improved performance using IR-GRIN lens elements in dual-band, MWIR-LWIR sensors. The SWaP and performance advantages of IR-GRIN lenses in platform-relevant dual-band imagers will be presented.

Optical systems are susceptible to saturation or damage caused by high power lasers. The major issue is to find a mechanism to protect from laser threats without interfering with the optical system performances. This paper presents a new approach in exploiting the laser energy itself to enable a dynamic response of a protection filter. We discuss an up conversion mechanism in which two or more photons of the threatening laser are absorbed by an up converting molecule following an energy transfer to a molecule that is able to change its absorption spectra and absorb in that laser wavelength range, thus creating a dynamic filter limiting high power lasers while allowing high transmittance for low intensity light.

Controlling for uniformity of an optical coating becomes increasingly difficult for optics with steep curvatures over a large aperture. The growth of a film will inevitably be affected as a function of deposition angle. By exploiting the porosity of a film grown at oblique angles, its refractive index can be tailored to specific applications. An anti-reflective coating deposited on a tilted Corning High-Purity Fused Silica (HPFS) 7980 substrate was characterized for surface and cross-sectional morphologies, crystalline structures, and spectroscopic homogeneity.

Scratch resistant anti-reflective (SRAR) coatings were developed on Gorilla Glass substrates. A reactive magnetron sputtering process was employed to enable desired layer hardness and refractive index. Optical modeling was performed to determine the effective hardness of the SRAR coatings, in an effort to reduce reflectance in the visible while maintaining high scratch resistance. Scratch resistance was evaluated by using a nano-indentation test. Broadband AR coatings were realized. Potential applications of the SRAR coatings for AD optics were discussed.

High power laser optical systems can suffer damage from uncoated optics due to undesirable Fresnel reflections. With high power lasers, traditional anti-reflection (AR) thin-film coated optics are susceptible to localized field enhancement regions, due to multiple boundaries, and experience laser induced damage on both entry and exit interfaces. Sub-wavelength random anti-reflective surface structures (rARSS) have been shown to have a higher laserinduced damage threshold than traditional AR coatings. Previously published work detailed nanosecond-pulsed laserinduced damage on rARSS on both single surface and dual surface of optical quality, planar, fused silica substrates at 1064 nm. This study details laser fatigue testing of double-sided rARSS samples via continuous wave, 2 kW ytterbiumfiber- laser irradiation (1075 nm). Laser output was focused to increase incident intensity at the initial interface. The laser spot was focused to ~ 60-μm-diameter (1/e²) yielding a maximum power density of 70.7 MW/cm². Laser power, test duration, and testing grid were controlled externally via LabVIEW software. Damage testing sites maintained the same laser power density (70.7 MW/cm²) and varied by irradiation time, incrementally from one minute up to one hour. It was determined that double-sided rARSS substrates have a higher damage threshold than thin-film AR coatings, showing no damage of the AR structures at power densities up to 70.7 MW/cm² and laser irradiation times up to one hour at each interrogation site, while thin-film samples have been reported to fail with power density as low as 2 MW/cm².

Dual-band infrared optical systems require complex designs to meet their optical and thermal requirements. This complexity involves an increase in the number of elements and, typically, a greater variety of substrate materials. Many of the elements are lenses, therefore requiring the maintenance of coating thickness uniformity and durability over curved surfaces. Coating thickness uniformity can be predicted using commercially available modeling software that takes into consideration the locations of sources, monitors, substrates and any motion of the parts during deposition. The coating chamber configuration can then be optimized for thickness uniformity. Coating environmental durability is more difficult to predict, however. It is commonly accepted that there is a correlation between the coating deposition angle, the porosity of the coating and its durability. The durability of a coating deposited on flat witnesses is not necessarily representative of that of the coating deposited over the surface of a curved lens. Therefore, the deposition angle distribution must also be taken into consideration when optimizing for coating uniformity. We discuss the optimization of a coating chamber configuration for the challenging geometry of a 6” diameter lens with a 6” radius of curvature. The configuration is optimized for both thickness uniformity and deposition angle distribution. Coating uniformity and durability are measured on a monolithic lens substrate as well as on witnesses arrayed in surrogate tooling simulating the lens surface. The coating durability on the witnesses and full lens are analyzed with respect to modelled uniformity and deposition angle distributions.

Ever since the human genome was first sequenced, scientists have been inspired by possibilities of using genomic information for medical research. In recent year, new generation sequencing platform to deliver complete genome sequence data with higher throughputs are to be built to conduct genomic studies on a large scale. This requires the development of a wide field multi-channel fluorescence imager system. The complexity of this optical system for human genome sequencing application would also have specific optical coating challenges. For the objective lens system, it requires selection of multiple glass types with normal and anomalous dispersions in order to successfully correct chromatic aberrations to diffraction-limited level over a broad wavelength spectrum. The challenge is anti-reflection (AR) coatings need to be coated over these multi-glass types with various refractive index from 1.43 to 1.8 and operate through an extended range of broad spectrum range. In addition, auto-fluorescence of optical components and coatings applied to the lenses are considered an isotropic generation of the secondary stray light inside the system. This is undesirable and should be minimized. This research work presents the AR coating design strategy to accommodate the multiple glass types in the lens system over a broadband application range and the investigation results of achieving low auto-fluorescence through material selection and coating process control.

Optical metasurfaces, two-dimensional counterparts of the metamaterials, are comprised of arrays of subwavelength engineered inclusions that can locally modify optical field and light–matter interactions, thus offering fascinating possibilities to realize unprecedented photonic phenomena. Here, a micro-structured optical coating or a hybrid multilayer structure is proposed. It is easy to achieve phase control over 2π by changing the geometric parameter, which is used to design gradient metasurface exhibiting anomalous reflection for linearly polarized light (1μm). By arranging the arrays elaborately, the efficiency can reach as high as 93.6%. Besides, reflective metalens taking advantage of the Pancharatnam-Berry phase is demonstrated. The electric field distribution unambiguously indicates that the metalens can focus the plane wave with high efficiency (60.3%). Such structure may find various potential applications in nanophotonics because of their high freedom to design metasurfaces.

Large sapphire crystals are currently being grown at II-VI Optical Systems with dimensions of approximately 12” x 36” x 0.300” thick via an Edge Defined Film Fed Growth (EFG) method. These crystals are being used to make large sapphire windows for aerospace applications which require high strength and optical performance in the visible to mid-wave infrared regions. In the following paper, II-VI OS will present material data for their EFG sapphire and compare it to that for sapphire grown via the HEM approach, a method which is also used at II-VI OS. Reported data includes index homogeneity evaluated over the entire grown crystal. Other properties to be presented are equibiaxial flexural strength, index of refraction, Knoop hardness, thermal expansion coefficient and modulus of elasticity. The results presented herein will demonstrate that the material performance of sapphire grown at II-VI OS by either method is entirely comparable.

Transparent ZnO–Bi₂O₃–B₂O₃ (ZBB) glasses were prepared using the melt quench technique. Various compositions of the glass containing stoichiometric ratios of Zn/Bi/B as well as some including As₂O₃ for redox control and LiNO₃ for use as nucleation species, were studied. ZBB glass-ceramics containing nanocrystallites have a potential for use as low-cost UV-MWIR optical devices such as microlenses, waveguides, and photonic crystals. Our goal was to exploit crystal growth in the ZBB systems by heat treatment in order to obtain transparent glass-ceramics that contain homogenous volume crystallization. Thermal behavior was studied using differential scanning calorimeter (DSC) measurements. Physical and optical characterizations included Raman spectroscopy to identify molecular connectivity, energy-dispersive X-ray spectroscopy (EDX) for elemental analysis, VIS/NIR transmission and reflection spectroscopy for optical bandgap and IR transmissivity, X-ray diffraction (XRD) to determine crystal phase, and transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED) to quantify size, number density, and identification of nanometer sized secondary phases. Heat treatments were used to nucleate and grow BiB₃O₆ and Bi2_ZnB₂O₇ nanocrystals in ZBB. We explored new compositions within the ZBB system and heat treatment techniques to assess the transformation of the amorphous glass phase into the crystalline phase. In-situ XRD and TEM imaging was employed to correlate nucleation temperature, heat treatment temperature, and heat treatment duration with induced crystal phase. BiB₃O₆, Bi₂ZnB₂O₇, and ZnO was found to grow on the surface of some compositions. Compositions and heat treatment procedures were developed to facilitate volume crystallization and reduce unwanted surface crystallization.

We review the potential and limitations of a temperature-dependent Raman Scattering Technique (RST) as a nondestructive optical tool to investigate the thermal properties of bulk Chalcogenide Glasses (ChGs). Conventional thermal conductivity measurement techniques employed for bulk materials cannot be readily extended to thin films created from the parent bulk. This work summarizes the state of the art, and discusses the possibility to measure more accurately the thermal conductivity of bulk ChGs with micrometer resolution using RST. Using this information, we aim to extend the method to measure the thermal conductivity on thin films. While RST has been employed to evaluate the thermal conductivity data of 2D materials such as graphene, molybdenum disulfide, carbon nanotubes and silicon, it has not been used to effectively duplicate data on ChGs which have been measured by traditional measurement tools. The present work identifies and summarizes the limitations of using RST to measure the thermal conductivity on ChGs. In this technique, the temperature of a laser spot was monitored using Raman Scattering Spectra, and efforts were made to measure the thermal conductivity of bulk AMTIR 1 (Ge₃₃As₁₂Se₅₅) and Ge_32.5As₁₀Se_57.5 ChGs by analyzing heat diffusion equations. To validate the approach, another conventional technique - Transient Plane Source (TPS) has been used for assessing the thermal conductivity of these bulk glasses. Extension to other more complicated materials (glass ceramics) where signatures from both the glassy matrix and crystallites, are discussed.

High-precision chalcogenide molded freeform micro-lenses were designed and produced to perfectly collimate and circularize mid-infrared Quantum Cascade Lasers (QCLs). The innovative micro-lens has an input surface with freeform contour to simultaneously converge the fast axis and further diverge the slow axis, while the output freeform surface collimates both axes. The 5-mm long freeform lens is such that the collimated output fast- and slow-axis beams are circular. This paper presents recent results on the chalcogenide molded freeform micro-lens prototypes specifically designed to collimate and circularize QCL at 9 micron.

Aluminum alloys containing ceramic particulate reinforcement produce a lightweight metal matrix composite (MMC) with enhanced mechanical and physical properties including higher modulus and vibration loss. This paper will discuss Al-SiC MMC’s made from mechanical alloyed (MA) powder. Consolidated MA powder can produce isotropic MMC’s with micron to submicron mean particulate reinforcement size, increasing mechanical properties in comparison to MMC’s with larger particle size plus results in a material that can be machined or metal worked using conventional methods. The microstructure, properties and emissivity of MMC’s MA’d with base aluminum alloys 6061B and 2124A will be presented including approved SAE-AMS compositions.

Graphene’s efficiency in providing plasmonics media for controlling light at nanoscale gives the necessary response at picosecond time ranges. A high-mobility grapheme monolayer is utilized to activate plasmons is one of the most promising to produce infrared radiation. The suggested methods are introduced in order to control the plasmonic media in metal-based plasmonics for nano-scale light manipulating. The electronic and optical properties of elemental metals are difficult to modify, especially by external means.