This PDF file contains the front matter associated with SPIE Proceedings Volume 11737, including the Title Page, Copyright Information, and Table of Contents.

In this paper we present techniques for measuring efficiently the optical properties of chalcogenide glasses. In particular we discuss methods for measuring refractive index and the variation of refractive index with temperature. We then apply these techniques to a new glass composition and demonstrate a high index of 3.26 @10 μm and a large thermo-optic coefficient of 1.99 ⋅ 10⁻⁴ K⁻¹. These properties make this glass a good candidate for replacing germanium.

NRL is developing new materials that transmit across wide wavelength ranges and will present recent results. MILTRAN is a new rugged optical ceramic that transmits visible through LWIR and is 3.5 times harder than ZnS and is well suited as an internal lens element. NRL-series moldable glasses transmit SWIR through LWIR and may be bonded to each other in an adhesive-free thermal process. NRL-200-series glasses transmit visible through MWIR and expand the glass map for multispectral lens designs. These new materials enable greater flexibility for designers of lenses for advanced defense applications and potentially reduce the size, weight and cost of next-generation optics.

Infrared optical materials are used to manufacture optical components that enable todays infrared systems. While there are many materials that transmit in the infrared, there are only a limited number that are commonly used in thermal imaging systems. The cost of these systems is an important consideration in both the commercial and military markets, and the optics occupy a significant portion of the overall bill of material. This is due to significant declines in detector costs while the optical materials and their associated feedstocks have declined less so; or if at all. Understanding the availability, market for, and cost of the feedstocks for these materials and their applicability to infrared optical materials provides valuable information for cost sensitive selection of infrared optical materials.

At the Naval Research Laboratory, we have developed several rugged oxide materials for optics applications. These materials include cubic sesquioxides (Y2O3 and Lu2O3) and spinel ceramics which transmit in the UV, visible, SWIR and MWIR wavelength region. These materials have superior mechanical and optical properties compared to the currently used materials on various Navy / DoD systems. The transparent and rugged ceramics are fabricated by the Hot press/HIP method using ultra-pure powder synthesized in-house and the resulting ceramics typically have excellent optical quality with no birefringence. In this paper, we present the optical properties of these rugged transparent ceramics and lens designs using these materials will be also discussed.

Precision glass molding (PGM) of chalcogenide lenses has become an enabling technology for high volume thermal imaging applications. The molding machines that facilitate this technology vary widely in design, functionality, and cost. The machines range from single-axis compact machines and large-scale fixed die machines to progressive transfer molding machines and highly customized systems for specialized applications such as wafer level molding. These technologies are compared and contrasted with specific attention paid to the intricacies of precision molding of chalcogenide glass.

We have proposed, designed, simulated and fabricated a holographic, low loss focusing lens with engineered nano-scaled features. This metastructure was designed to converge off-axis infrared (IR) radiation and created by patterning a dielectric surface. To leverage previous efforts for baseline data, we chose an array of nano-pillars which varied in widths although were fixed in both height and periodicity. We achieved the desired Gradient Index (GRIN) and resulting focus length, by engineering the effective index of refraction across the metasurface which was achieved from varying the material-to-air ratio. This allowed us to create a parabolic phase gradient, thereby generating an effective optical density that peaks in the appropriate sector of the lens while gradually degrading towards the perimeter of the lens in Figure 1. Lenslets with varying patterns, dependent upon their position in the array, were designed, simulated and fabricated.

Silicon (n~3.4) and germanium (n~4.0) are harmless and conventional infrared optical materials. SiGe alloys, mixed crystals of Si and Ge, permit a flexible Si/Ge ratio in the crystals, which results in a refractive-index gradient. We report on the Travelling Liquidus-Zone (TLZ) method for growing both gradient and homogeneous concentration SiGe crystals. The wavelength dependences of the refractive indices from 2.0 to 20 μm of the 20 mm diameter Si1-XGeX (x=0.32 and 0.63), Si and Ge disks were measured using an ellipsometry. An infrared lens system made of germanium and homogeneous concentration SiGe crystals has been designed.

Reduced SWaP-C is one of the hottest trends in thermal imaging requirements. It allows thermal imaging systems to be used for a range of new applications, including UAVs and drones in the commercial, homeland security, and defense industries, most notably for long range observation. Meeting reduced SWAP-C requirements involves the design and manufacture of high performance, miniaturized, and affordable thermal imaging components that also allow for long operational ranges. This can be achieved through the use of continuous zoom lenses with innovative optical and mechanical designs, manufactured with the latest cutting-edge technologies. Recently, Ophir launched a range of new zoom lenses that meets the challenging requirements of low SWaP-C and long operational ranges, ideal for integration with UAVs and drones.