This PDF file contains the front matter associated with SPIE Proceedings Volume 10374, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

One of the driving structural requirements of the Habitable Exo-Planet (HabEx) telescope is to maintain Line Of Sight (LOS) stability between the Primary Mirror (PM) and Secondary Mirror (SM) of ≤ 5 milli-arc seconds (mas). Dynamic analyses of two configurations of a proposed HabEx 4 meter off-axis telescope structure were performed to predict effects of a vibration input on primary/secondary mirror alignment. The dynamic disturbance used as the forcing function was the James Webb Space Telescope reaction wheel assembly vibration emission specification level. The objective of these analyses was to predict “order-of-magnitude” performance for various structural configurations which contribute to efforts in defining the HabEx structural design’s global architecture. Two variations of the basic architectural design were analyzed. Relative motion between the PM and the SM for each design configuration are reported.

The point spread function (PSF) for astronomical telescopes and instruments depends not only on geometric aberrations and scalar wave diffraction, but also on the apodization and wavefront errors introduced by coatings on reflecting and transmitting surfaces within the optical system. Geometrical ray tracing provides incomplete image simulations for exoplanet coronagraphs with the goal of resolving planets with a brightness less than 10^-9 of their star located within 3 Airy disk radii. The Polaris-M polarization analysis program calculates uncorrected coating polarization aberrations couple around 10^-5 light into crossed polarized diffraction patterns about twice Airy disk size. These wavefronts not corrected by the deformable optics systems. Polarization aberrations expansions have shown how image defects scale with mirror coatings, fold mirror angles, and numerical aperture.

The JWST Optical Telescope Element (OTE) assembly is the largest optically stable infrared-optimized telescope currently being manufactured and assembled, and is scheduled for launch in 2018. The JWST OTE, including the 18 segment primary mirror, secondary mirror, and the Aft Optics Subsystem (AOS) are designed to be passively cooled and operate near 45K. These optical elements are supported by a complex composite backplane structure. As a part of the structural distortion model validation efforts, a series of tests are planned during the cryogenic vacuum test of the fully integrated flight hardware at NASA JSC Chamber A. The successful ends to the thermal-distortion phases are heavily dependent on the accurate temperature knowledge of the OTE structural members. However, the current temperature sensor allocations during the cryo-vac test may not have sufficient fidelity to provide accurate knowledge of the temperature distributions within the composite structure. A method based on an inverse distance relationship among the sensors and thermal model nodes was developed to improve the thermal data provided for the nanometer scale WaveFront Error (WFE) predictions. The Linear Distance Weighted Interpolation (LDWI) method was developed to augment the thermal model predictions based on the sparse sensor information. This paper will encompass the development of the LDWI method using the test data from the earlier ‘pathfinder’ cryo-vac tests, and the results of the notional and as tested WFE predictions from the structural finite element model cases to characterize the accuracies of this LDWI method.

We propose a fiber-optic sensor structure for simultaneous strain and temperature monitoring in cryogenic conditions. The polymer coated fiber Bragg grating sensor makes it a suitable candidate for cryogenic temperature measurement. FBG have been shown to have an enhanced sensitivity of 48 pm °C^-1 from -185 to 25 °C. The cross-sensitivity problem has been solved by introducing a glass capillary tube to encapsulate the coated FBG. The thermal expansion of capillary material was compensated by cleaving the one end of FBG free and the other end with the temperature resistant epoxy resins. Experiments results validate the proposed method can successfully monitor the strain and temperatures at cryogenic temperatures.

Optical system performance is easily affected by variable surrounding conditions, including the precision optical system, as its performance is changed with flow field in the air or surrounding water. The air content of water vapor, carbon dioxide concentration, and dry air has a ratio that will affect the air refractive index. Water is another material of general optical systems, affected by surrounding conditions as well. Lithography and the microscope lens are commonly used for contact with water, with their refractive nature, changed by the pressure and density in the flow field. In addition, temperature and light wavelength are two important parameters of the air and water refractive index. This study calculates fluid field pressure and velocity distribution by Computational Fluid Dynamics (CFD) software, and then transfers it to air and water refractive index differences in the optical system. We also evaluate Optical Path Difference (OPD) with fluid field changes, which can improve optical design and system alignment progress by avoiding surrounding condition changes.

Icing causes substantial problems in the integrity of large-scale wind turbines. In this work, a fiber-optic sensor system for detection of icing with an arrayed waveguide grating is presented. The sensor system detects Fresnel reflections from the ends of the fibers. The transition in Fresnel reflection due to icing gives peculiar intensity variations, which categorizes the ice, the water, and the air medium on the wind turbine blades. From the experimental results, with the proposed sensor system, the formation of icing conditions and thickness of ice were identified successfully in real time.

Diffractive optics enable applications requiring high power laser focusing and beam shaping. The ability of such components to resist damage is of mounting importance as lasers attain higher power levels. Diffractive optics inherently contain discontinuities that can enhance electric field distributions within the component. Researchers have previously analyzed subwavelength, anti-reflective gratings for geometrical field enhancement effects, but conventional diffractive elements have not received as much attention. In this paper, we apply rigorous electromagnetic simulations to multi-level diffractive optics to explore potential connections between basic grating parameters (period, depth, number of levels), geometrical field enhancement, and laser damage.

Exoplanet science requires extreme wavefront stability (10 pm change/10 minutes), so every source of wavefront error (WFE) must be characterized in detail. This work illustrates the testing and characterization process that will be used to determine how much surface figure error (SFE) is produced by mirror substrate materials’ CTE distributions. Schott’s extremely lightweight Zerodur mirror (ELZM) was polished to a sphere, mounted, and tested at Marshall Space Flight Center (MSFC) in the X-Ray and Cryogenic Test Facility (XRCF). The test transitioned the mirror’s temperature from an isothermal state at 292K to isothermal states at 275K, 250K and 230K to isolate the effects of the mirror’s CTE distribution. The SFE was measured interferometrically at each temperature state and finite element analysis (FEA) has been completed to assess the predictability of the change in the mirror’s surface due to a change in the mirror’s temperature. The coefficient of thermal expansion (CTE) distribution in the ELZM is unknown, so the analysis has been correlated to the test data. The correlation process requires finding the sensitivity of SFE to a given CTE distribution in the mirror. A novel hand calculation is proposed to use these sensitivities to estimate thermally induced SFE. The correlation process was successful and is documented in this paper. The CTE map that produces the measured SFE is in line with the measured data of typical boules of Schott’s Zerodur glass.

Modeling photoemission using the Moments Approach (akin to Spicer’s “Three Step Model”) is often presumed to follow simple models for the prediction of two critical properties of photocathodes: the yield or “Quantum Efficiency” (QE), and the intrinsic spreading of the beam or “emittance” ε_n;rms. The simple models, however, tend to obscure properties of electrons in materials, the understanding of which is necessary for a proper prediction of a semiconductor or metal’s QE and ε_n;rms. This structure is characterized by localized resonance features as well as a universal trend at high energy. Presented in this study is a prototype analysis concerning the density of states (DOS) factor D(E) for Copper in bulk to replace the simple three-dimensional form of D(E) = (m/π² h³)p2mE currently used in the Moments approach. This analysis demonstrates that excited state spectra of atoms, molecules and solids based on density-functional theory can be adapted as useful information for practical applications, as well as providing theoretical interpretation of density-of-states structure, e.g., qualitatively good descriptions of optical transitions in matter, in addition to DFT’s utility in providing the optical constants and material parameters also required in the Moments Approach.

We propose a novel aqueous ethanol fiber-optic sensor which is based on Fresnel reflection. It is functionalized with a thin-layer of an ethanol-sensitive graphene oxide (GO) coating on a single mode optical fiber end. The trace of ethanol concentration was measured by the variations in Fresnel reflection intensity and the optical properties of graphene oxide. The sensor output was obtained successfully in response to aqueous ethanol concentration from 20% to 100%. The fiber end with GO film exhibited real- time and remote measurement of ethanol concentration with high precision.

Recently there is a growing interest to the head up and head mounted systems. There are many variants of implementation of the head-mounted display system for various purposes with different characteristics. The configuration of the system is highly affected by both type of the image generator and the type of the used combiner. We have considered several variants of the layout of the systems and compare their characteristics including the package and image quality. The systems were designed for operating with the same image generator.

Recently there has been an intensive development of intelligent industrial equipment that is highly automated and can be rapidly adjusted for certain details. This equipment can be robotics systems, automatic wrappers and markers, CNC machines and 3D printers. The work equipment considered is the system for selective curing of photopolymers using a UV-laser and UV-radiation in such equipment that leads to additional technical difficulties. In many cases for transporting the radiation from the laser to the point processed, a multi-mirror system is used: however, such systems are usually difficult to adjust. Additionally, such multi-mirror systems are usually used as a part of the equipment for laser cutting of metals using high-power IR-lasers. For the UV-lasers, using many mirrors leads to crucial radiation losses because of many reflections. Therefore, during the development of the optical system for technological equipment using UV-laser we need to solve two main problems: to transfer the radiation for the working point with minimum losses and to include the system for controlling/handling the radiation spot position. We introduce a system for working with UV-lasers with 450mW of power and a wavelength of 0.45 μm based on a fiber system. In our modelling and design, we achieve spot sizes of about 300 μm, and the designed optical and mechanical systems (prototypes) were manufactured and assembled. In this paper, we present the layout of the technological unit, the results of the theoretical modelling of some parts of the system and some experimental results.

This work provides a numerical analysis of elastic light scattering by a fused silica capillary for noninvasive sensing of the refractive index for the purposes of capillary electrophoresis (CE). A capillary containing the sample liquid is illuminated by a beam of light of low temporal coherence. The scattering far-field pattern is analyzed in the vicinity of multiple primary rainbows. The paper offers both explanation of the scattering mechanisms contributing to the far-field intensity pattern based on numerical simulations as well as an analysis of the sensitivity of the measurement data to changes in the refractive index.

An analysis is presented that provides a density of states (DOS or D(E)) factor for Cs₃Sb in the calculation of its quantum efficiency QE and emittance ε_n;rms using a Moments Approach. The analysis is based on density functional theory (DFT) adapted for the practical application of treating photoemission from bulk metal and semiconductor materials, and the interfaces between them. The Moments approach treats the processes of absorption, transmission and emission separately, for which DFT affects parameters and processes associated with each step, of which D, the optical constants n and k, and materials parameters such as effective mass m_n and band gap E_g are paramount. Such factors are required to provide the components of an evaluation similar to the Tsu-Esaki formula for calculating current density over and through and over barriers, and will become more important when a proper quantum mechanical treatment of the emission barrier is considered beyond the simplistic thermal model (transmission probability is unity only for energy levels in excess of the barrier height and zero otherwise). Such features are expected to be far more consequential if the barrier supports resonant levels, e.g., heterostructures.

This paper presents the effect of laser ablation parameters on optical limiting properties of silver nanoparticles. The current applications of lasers such as range finding, guidance, detection, illumination and designation have increased the potential of damaging optical imaging systems or eyes temporary or permanently. The applications of lasers introduce risks for sensors or eyes, when laser power is higher than damage threshold of the detection system. There are some ways to protect these systems such as neutral density (nd) filters, shutters, etc. However, these limiters reduce the total amount of light that gets into the system. Also, response time of these limiters may not be fast enough to prevent damage and cause precipitation in performance due to deprivation of transmission or contrast. Therefore, optical limiting filters are needed that is transparent for low laser intensities and limit or block the high laser intensities. Metal nanoparticles are good candidates for such optical limiting filters for ns pulsed lasers or CW lasers due to their high damage thresholds. In this study we investigated the optical limiting performances of silver nanoparticles produced by laser ablation technique. A high purity silver target immersed in pure water was ablated with a Nd:YAG nanosecond laser at 532 nm. The effect of altering laser power and ablation time on laser ablation efficiency of nanoparticles was investigated experimentally and optimum values were specified. Open aperture Zscan experiment was used to investigate the effect of laser ablation parameters on the optical limiting performances of silver nanoparticles in pure water. It was found that longer ablation time decreases the optical limiting threshold. These results are useful for silver nanoparticles solutions to obtain high performance optical limiters.

Fractal-like aggregates are usually modeled as monodisperse particles positioned in point contact. However, in reality, much more advanced connections between primary particles exist. In this work, new parameters for measuring both the intersection level and the neck level were introduced. Then, the impact of the connection type on the spectral behavior of fractal-like WO3 aggregates was studied. For light scattering simulations, in the visible spectrum, the ADDA algorithm was used. The results prove that necks have strong impact on the spectral behavior of WO₃ aggregates and connections, which exist between primary particles, should not be excluded from models.