Digital augmentation of direct view optics like riflescopes allows viewing of the scene with near-zero latency while simultaneously offering increased situational awareness from fielded sensors and systems data. Existing solutions to digitally augment a direct view optic add a considerable amount of weight/size, require the digital projection system to be designed into each specific viewing optic, or interfere with operational function of the optic. Here we present an externally mounted, compact optical waveguide capable of displaying information such as ballistic data overlaid onto the field-of-view of a riflescope. Volume phase holograms form the input/output couplers and the pupil expander of the waveguide. The holographic waveguide satisfies the contrast ratio needed for daylight bright environments, allows for operability of the diopter adjustment, minimally impacts eye relief, and requires no refocusing to view the symbology.
Aircraft head-up displays (HUDs) have historically used monochromatic symbology to relay critical information to the pilot. The main reasons for using a single color are the favorable spectral overlap of the green phosphors of the emission source with the peak of human luminance sensitivity, and the difficulty of achieving performance requirements at two widely separated wavelengths. However, using at least one additional color could greatly enhance situational awareness and effectiveness by color coding information or creating multi-functional symbology. Here we show the optical system design of a dual-color aircraft HUD which is enabled by a holographic combiner and a digital light processing chip. We found that the main optical requirements of an aircraft HUD, namely resolution and luminance, can be met for the two wavelengths using a multilayer hologram which selectively diffracts each color to the pilot. By use of a hologram as the combiner, the direct view to the pilot can be free of both tint and forward light signature. Furthermore, the holographic combiner means that a steeper input angle can be used, leading to a more compact optical path compared to traditional reflective or refractive counterparts. The results demonstrate a path forward for dual-color aircraft HUD based on a hologram/digital chip combination.
The authors propose a digital sensor figure of merit (FOM) to describe the performance of digital night vision sensors operating in low-light conditions with a single-number parameter in a manner directly comparative to the FOM of analog image intensifier tubes (IIT). Currently, this first iteration single-valued digital sensor FOM is the product of measured sensor limiting resolution and sensor signal-to-noise ratio using alternative but equivalent techniques to IIT FOM measurements.
Remote sensing techniques offer the only viable opportunity to learn more about the estimated thousands of small pieces of debris that orbit the Earth near the GEO belt. In previous work, multispectral optical and infrared sensing techniques have been employed to characterize debris and the population of small GEO belt debris. This paper examines an infrared remote sensing model for GEO belt debris and the uncertainty in the remote sensing techniques, with the aim of suggesting a way to improve upon previous attempts to characterize the population of GEO belt debris by either reducing uncertainty or improving radiometric sensitivity. Analytical methods applied to measurements of GEO belt debris data, in addition to detailed modeling of notional sensors in infrared wavebands are presented.
A key application of metallic nanostructures is enhancement of the radiative decay rates of quantum emitters. In this contribution we investigate control of emission dynamics of semiconductor quantum dots (QDs) using combination of both metal oxides and plasmonic effects of gold thinfilms. Different metal oxides, including Cu, Ag and Al oxides are investigated. We show how such oxides can dramatically change the decay of QDs via photocatalytic processes in the absence and presence of plasmonic fields. The outcomes show the distinct impact of such oxides, ranging from total annihilation of QD emission to their plasmonic revival via Purcell effect.
NASA has described the need for rugged, compact spectrometers for deep ultraviolet (DUV) analysis of atmospheric properties during the entry, descent, and landing (EDL) phase of the mission profile for planetary landing craft. The EDL phase presents a brief opportunity to gather useful altitude profiles of atmospheric components and pressures. However, EDL is a high-risk phase and presents severe challenges to instrument design, including large temperature changes over short periods and payload restrictions. Therefore, the preferred features of an EDL spectrometer are compact design, stable performance across wide temperatures, DUV sensitivity, and simple temperature management systems. In this paper, a compact EDL spectrometer is described, which includes the system-level optical design and analysis of the novel silicon-carbide integrated circuits.
Chemical sensing based on Localized Surface Plasmonic Resonances (LSPR) and the ultra-sharp optical features of surface lattice resonances (SLR) of arrays of metallic nanoantennas have attracted much attention. Recently we studied biosensing based on the transition between LSPR and SLR (hybridization phase), demonstrating significantly higher refractive index sensitivity than each of these resonances individually. In this contribution we study the impact of size and shape of the metallic nanoantennas on the hybridization process and the way they influence application of this process for biosensing, wherein miniscule variation of the refractive index of the environment leads to dramatic changes in the spectral properties of the arrays.
We show arrays of large gold nanodisks on glass substrates can support strong optical features with narrow spectral widths associated with their collective plasmonic-lattice modes. Our results show that these modes can offer significant sensitivity to the refractive index of the environment, far more than those of individual nanodisks. We show the visible collective modes supported by such arrays can distinctively detect a monolayer of biotin with high resolution. We use donor (CdSe/ZnS) and acceptor (CuInS/ZnS) quantum dots to investigate the field properties of these arrays after deposition of a thick layer of a silicon. We demonstrate a distinct increase of emission of CuInS/ZnS quantum dots, indicating the possibility of enhancement of energy transfer between these two types of quantum dots.
It is well known that irradiation of colloidal quantum dots can dramatically enhance their emission efficiencies, leading to so-called photoinduced fluorescence enhancement (PFE). This process is the result of the photochemical and photophysical properties of quantum dots and the way they interact with the environment in the presence of light. It has been shown that such properties can be changed significantly using metal oxides. Using spectroscopic techniques, in this paper we investigate emission of different types of quantum dots (with and without shell) in the presence of metal oxides with opposing effects. We observed significant increase of PFE when quantum dots are deposited on about one nanometer of aluminum oxide, suggesting such oxide can profoundly increase quantum yield of such quantum dots. On the other hand, copper oxide can lead to significant suppression of emission of quantum dots, making them nearly completely dark instantly.
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