• 1720-nm narrow-linewidth all-fiber ring laser based on thulium-doped fiber

      Zhang, Junxiang; Sheng, Quan; Sun, Shuai; Shi, Chaodu; Fu, Shijie; Shi, Wei; Yao, Jianquan; Univ Arizona, Coll Opt Sci (SPIE-INT SOC OPTICAL ENGINEERING, 2020-02-21)
      A 1720-nm thulium-doped all-fiber laser based on a ring-cavity configuration is demonstrated. The long-wavelength lasing near the 1.9-mu m thulium emission peak was suppressed using a wavelength division multiplexer and single-mode-multimode-single-mode (SMS) fiber device, which together served as a short-pass filter instead of the grating devices usually used in 1.7-mu m thulium fiber lasers. A stable hundred-milliwatt-level 1720-nm laser output with a narrow spectral linewidth on the order of gigahertz was obtained after optimizing the output coupling, the active fiber length and the SMS device.
    • 3D augmented reality with integral imaging display

      Shen, Xin; Hua, Hong; Javidi, Bahram; Univ Arizona, Coll Opt Sci (SPIE-INT SOC OPTICAL ENGINEERING, 2016-06-01)
      In this paper, a three-dimensional (3D) integral imaging display for augmented reality is presented. By implementing the pseudoscopic-to-orthoscopic conversion method, elemental image arrays with different capturing parameters can be transferred into the identical format for 3D display. With the proposed merging algorithm, a new set of elemental images for augmented reality display is generated. The newly generated elemental images contain both the virtual objects and real world scene with desired depth information and transparency parameters. The experimental results indicate the feasibility of the proposed 3D augmented reality with integral imaging.
    • 3D visualization of optical ray aberration and its broadcasting to smartphones by ray aberration generator

      Hellman, Brandon; Bosset, Erica; Ender, Luke; Jafari, Naveed; McCann, Phillip; Nguyen, Chris; Summitt, Chris; Wang, Sunglin; Takashima, Yuzuru; Univ Arizona (SPIE-INT SOC OPTICAL ENGINEERING, 2017-11-27)
      The ray formalism is critical to understanding light propagation, yet current pedagogy relies on inadequate 2D representations. We present a system in which real light rays are visualized through an optical system by using a collimated laser bundle of light and a fog chamber. Implementation for remote and immersive access is enabled by leveraging a commercially available 3D viewer and gesture-based remote controlling of the tool via bi-directional communication over the Internet.
    • 4×2 HEB receiver at 4.7 THz for GUSTO

      Silva, Jose R.; Mirzaei, Behnam; Laauwen, Wouter; Hu, Qing; Groppi, Christopher E.; Walker, Christopher; Gao, Jian-Rong; More, Nikhil; Young, Abram; Khalatpour, Ali; et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2018)
      GUSTO will be a NASA balloon borne terahertz observatory to be launched from Antarctica in late 2021 for a flight duration of 100-170 days. It aims at reviewing the life cycle of interstellar medium of our galaxy by simultaneously mapping the three brightest interstellar cooling lines: [OI] at 4.7 THz, [CII] at 1.9 THz, and [NII] at 1.4 THz; along 124 degrees of the galactic plane and through a part of the Large Magellanic Cloud. It will use three arrays of 4x2 mixers based on NbN hot electron bolometers (HEBs), which are currently the most sensitive mixers for high resolution spectroscopic astronomy at these frequencies. Here we report on the design of a novel 4.7 THz receiver for GUSTO. The receiver consists mainly of two subsystems: a 4x2 HEB quasi-optical mixer array and a 4.7 THz multi-beam LO. We describe the mixer array, which is designed as a compact monolithic unit. We show, for example, 10 potential HEB detectors with the state of the art sensitivity of 720 K measured at 2.5 THz. They have a variation in sensitivity smaller than 3%, while also meeting the LO uniformity requirements. For the multi-beam LO we demonstrate the combination of a phase grating and a single QCL at 4.7 THz, which generates 8 sub-LO beams, where the phase grating shows an efficiency of 75%. A preliminary concept for the integrated LO unit, including QCL, phase grating and beam matching optics is presented.
    • The 6.5-m MMT Telescope: status and plans for the future

      Williams, G. Grant; Ortiz, R.; Goble, W.; Gibson, J. D.; Univ Arizona, MMT Observ; MMT Observatory (United States); MMT Observatory (United States); MMT Observatory (United States); MMT Observatory (United States) (SPIE-INT SOC OPTICAL ENGINEERING, 2016-08-08)
      The MMT Observatory, a joint venture of the Smithsonian Institution and the University of Arizona, operates the 6.5-m MMT telescope on the summit of Mount Hopkins approximately 45 miles south of Tucson, AZ. The upgraded telescope has been in routine operation for nearly fifteen years and, as such, is a very reliable and productive general purpose astronomical instrument. The telescope can be configured with one of three secondary mirrors that feed more than ten instruments at the Cassegrain focus. In this paper we provide an overview of the telescope, its current capabilities, and its performance. We will review the existing suite of instruments and their different modes of operation. We will describe some of the general operations challenges and strategies for the Observatory. Finally, we will discuss plans for the near-term future including technical upgrades, new instrumentation and routine queue operation of MMIRS and Binospec.
    • The abductive approach to synthetic autonomous reasoning

      Baker, Victor; Univ Arizona, Dept Hydrol & Atmospher Sci (SPIE-INT SOC OPTICAL ENGINEERING, 2019-05-13)
      Abductive inference, as defined by Charles S. Peirce, involves (1) observation of a surprising fact, (2) formulating (guessing) a proposition which, if true, would explain this fact as a matter of course, (3) and provisional acceptance of the proposition as true, (4) leading to its being taken as a premise for subsequent deduction, the consequences of which will then be related to further observations via induction-surprises from which can then trigger new abductive inferences, and so forth. Peirce limited this process to human reasoning because he viewed thought as a semiosis (flow of signs) continuous between the human mind and the world, such that (1) the human subject is in thought, as opposed to thought being in the subject, and that (2) there is an intrinsic ability of human beings to "guess right" as a consequence of this continuity of mind and world. The challenge posed by this view of thinking is that, unlike a human subject, any vehicle for autonomous reasoning is a newly created object that is separate from the world. It cannot be what Martin Heidegger termed a "being-in-the-world" because of the artificial separation of its thought from the world viewed as semiosis.
    • Aberrations of zoom lens kernel

      Sasián, José; Univ Arizona, James C Wyant Coll Opt Sci (SPIE-INT SOC OPTICAL ENGINEERING, 2019-09-09)
      This paper discusses the aberrations of a zoom lens kernel and a method to determine them. Separating the kernel aberrations provides insight into the zoom lens design process and helps the process by decoupling design tasks. The design of a zoom lens is discussed, step by step, and some alternate kernel solutions are shown. A technique for controlling uniform aberrations is discussed, and a reverse ray tracing method for displaying kernel aberrations is presented. The role of pupil coma in controlling distortion is also discussed.
    • Acoustic characterization of two megasonic devices for photomask cleaning

      Zanelli, Claudio; Giridhar, Dushyanth; Keswani, Manish; Okada, Nagaya; Hsu, Jyhwei; Yam, Petrie; Univ Arizona; Onda Corp. (United States); Onda Corp. (United States); The Univ. of Arizona (United States); et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2016-10-05)
      Wet photomask cleaning relies on megasonic agitation to enhance the process, but there are many challenges to reliably maximize particle removal efficiency (PRE) and minimize damage. With the shift to pellicle-free EUV masks, photomask processes are more vulnerable to contamination, increasing the urgency to improve the cleaning process. This difficulty is largely due to the unavailability of appropriate measurement of the acoustic field. Typically all that is known about the acoustic output is the driving frequency and the electric power delivered to a transducer, both global parameters that tell little about the field distribution over the substrate, the actual amplitude of the sound at the substrate, or the levels of cavitation (stable and transient) present at the substrate. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).
    • Acoustic source localization in an anisotropic plate without knowing its material properties: a new approach

      Park, Won Hyun; Packo, Pawel; Kundu, Tribikram; Univ Arizona, Dept Aerosp & Mech Engn; Univ Arizona, Dept Civil Engn & Engn Mech; Univ. of Arizona (United States); AGH Univ. of Science and Technology (Poland); Univ. of Arizona (United States) (SPIE-INT SOC OPTICAL ENGINEERING, 2016-04-01)
      A number of techniques are available for acoustic source localization in isotropic plates without knowing the material properties of the plate. However, for a highly anisotropic plate acoustic source localization requires some knowledge of the plate material properties or its group velocity profile. In absence of this information one requires a large number of sensors to predict the acoustic source point in the plate. All proposed techniques for acoustic source localization with a few sensors assume the straight line propagation of waves from the source to the receiving sensor with an average group velocity when the plate material properties are not known. However, this assumption is not true for an anisotropic plate. Although the currently available techniques work well for weakly anisotropic plates since the wave path does not deviate significantly from the straight line propagation they fail miserably for highly anisotropic plates. In this paper acoustic source is localized in an anisotropic plate when non-circular wave front is generated. Direction vectors of wave fronts are obtained from the Time-Difference-Of-Arrivals (TDOA) at three sensors placed in a cluster. Four such direction vectors are then utilized in geometric vector analysis to accurately obtain the acoustic source location. The proposed technique is illustrated on an orthotropic plate that generates rhombus shaped wave front. It should be noted that the proposed technique does not require wave propagation along a straight line from the source to the sensor. It also does not need the knowledge of the material properties of the plate.
    • Acoustic source localization in anisotropic plates without knowing their material properties: an experimental investigation

      Sen, Novonil; Gawroński, Mateusz; Packo, Pawel; Uhl, Tadeusz; Kundu, Tribikram; Univ Arizona, Dept Civil & Architectural Engn & Mech; Univ Arizona, Dept Aerosp & Mech Engn (SPIE-INT SOC OPTICAL ENGINEERING, 2019-04-01)
      An integral aspect of modern infrastructural engineering is to constantly monitor the health of a structure either actively or passively in order to ensure its safe performance throughout the design life. For passive structural health monitoring, it is important to estimate the location of an acoustic source that may be caused by events such as impact of a foreign object with the structure, failure of a structural element, formation of cracks, etc. Such an acoustic source generates acoustic waves that propagate through the medium. These waves can be captured by ultrasonic sensors mounted on the structure at some pre-selected locations and, subsequently, analyzed to predict the location of the acoustic source. Over the years, several researchers have proposed techniques for acoustic source localization in both isotropic and anisotropic structures. While acoustic source localization in isotropic structures is relatively simple, introduction of anisotropy adds a layer of difficulty to the problem due to the fact that waves do not propagate with the same speed in all directions. This study presents acoustic source localization techniques for anisotropic plates based on the analysis of the wave front shapes typically observed in anisotropic plates and presents experimental verification of the techniques. Three different geometric shapes are considered as the assumed wave front shapes: a rhombus, an ellipse and a parametric curve. A slightly modified version of the rhombus-based technique from the original approach is proposed. The experimental study is performed on two plates with different degrees of anisotropy.
    • Acoustic source localization in non-homogenous plates

      Yin, Shenxin; Cui, Zhiwen; Kundu, Tribikram; Univ Arizona, Dept Civil & Architectural Engn & Mech (SPIE-INT SOC OPTICAL ENGINEERING, 2019-04-01)
      In a nonhomogeneous specimen, if the acoustic source and receiving sensors are located in different media then the acoustic source localization becomes very difficult. In this paper, a recently developed source localization technique is extended to non-homogeneous plates by appropriately considering and modeling the refraction phenomenon. The modified technique is applied to two-layered structure. The proposed new technique gives a relatively simple way to localize the acoustic source without the need to solve a system of nonlinear equations, and thus it avoids the problem of multiplicity, converging to local minima instead of global minimum and giving wrong solution. The proposed technique works for both isotropic and anisotropic structures. The finite element simulation shows that this modified technique considering refraction at material interfaces can localize the acoustic source better than when this modification is not considered.
    • An Adaptive Hierarchical Approach to Lidar-based Autonomous Robotic Navigation

      Brooks, Alexander J. -W.; Fink, Wolfgang; Tarbell, Mark A.; Univ Arizona, Coll Engn, Visual & Autonomous Explorat Syst Res Lab (SPIE-INT SOC OPTICAL ENGINEERING, 2018)
      Planetary missions are typically confined to navigationally safe environments, leaving areas of interest in rugged and/or hazardous terrain largely unexplored. Identifying and avoiding possible hazards requires dedicated path planning and limits the effectiveness of (semi-)autonomous systems. An adaptable, fully autonomous design is ideal for investigating more dangerous routes, increasing robotic exploratory capabilities, and improving overall mission efficiency from a science return perspective. We introduce hierarchical Lidar-based behavior motifs encompassing actions, such as velocity control, obstacle avoidance, deepest path navigation/exploration, and ratio constraint, etc., which can be combined and prioritized to foul' more complex behaviors, such as free roaming, object tracking, etc., as a robust framework for designing autonomous exploratory systems. Moreover, we introduce a dynamic Lidar environment visualization tool. Developing foundational behaviors as fundamental motifs (1) clarifies response priority in complex situations, and (2) streamlines the creation of new behavioral models by building a highly generalizable core for basic navigational autonomy. Implementation details for creating new prototypes of complex behavior patterns on top of behavior motifs are shown as a proof of concept for earthly applications. This paper emphasizes the need for autonomous navigation capabilities in the context of space exploration as well as the exploration of other extreme or hazardous environments, and demonstrates the benefits of constructing more complex behaviors from reusable standalone motifs. It also discusses the integration of behavioral motifs into multi-tiered mission architectures, such as Tier-Scalable Reconnaissance.
    • Adaptive optics capabilities at the Large Binocular Telescope Observatory

      Christou, J. C.; Brusa, G.; Conrad, A.; Esposito, S.; Herbst, T.; Hinz, P.; Hill, J. M.; Miller, D. L.; Rabien, S.; Rahmer, G.; et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2016-07-26)
      We present an overview of the current and future adaptive optics systems at the LBTO along with the current and planned science instruments they feed. All the AO systems make use of the two 672 actuator adaptive secondary mirrors. They are (1) FLAO (NGS/SCAO) feeding the LUCI NIR imagers/spectrographs; (2) LBTI/AO (NGS/SCAO) feeding the NIR/MIR imagers and LBTI beam combiner; (3) the ARGOS LGS GLAO system feeding LUCIs; and (4) LINO-NIRVANA - an NGS/MCAO imager and interferometer system. AO performance of the current systems is presented along with proposed performances for the newer systems taking into account the future instrumentation.
    • Adaptive optics correction using coherently illuminated diffractive objects

      Finan, Emily; Milster, Tom; Kim, Young Sik; Univ Arizona, Coll Opt Sci (SPIE-INT SOC OPTICAL ENGINEERING, 2019-08-30)
      Adaptive Optics (AO) is an established technique for improving image quality and compensating for aberrations induced by focusing through samples with varying thickness and refractive index. Future optical data storage schemes with multiple data layers may require the correction capabilities of AO systems. However, the diffractive phase introduced by light reflected from optical storage media might be problematic for high-performance systems. A laser beam focused onto grooved media has a reflection with a baseball-shaped variation in the pupil, caused by the overlap in diffracted orders with the zero-order reflection. This pupil variation is significant in intensity, and simulations and experiments show that there is an associated small variation in phase. If the diffractive phase is sufficiently small, measurement of the total phase with aberrations by a wavefront sensor could enable application of AO correction with diffractive media samples. Simulations and experiments are presented to examine the capability of an adaptive optics microscope system to compensate for diffractive effects with a coherently illuminated sample. AO systems are commonly implemented with incoherent objects, but this could be extended to other applications by characterizing the performance of an AO system with a coherent reflection from a diffractive surface. Data storage media are used as targets for investigating these intensity and phase variations caused by coherence effects, with well-defined grating parameters creating diffraction patterns that are modeled and verified experimentally. There are potential applications outside of data storage, such as coherent freespace optical communication.
    • Advanced structural design for precision radial velocity instruments

      Baldwin, Dan; Szentgyorgyi, Andrew; Barnes, Stuart; Bean, Jacob; Ben-Ami, Sagi; Brennan, Patricia; Budynkiewicz, Jamie; Chun, Moo-Young; Conroy, Charlie; Crane, Jeffrey D.; et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2016-07-22)
      The GMT-Consortium Large Earth Finder (G-CLEF) is an echelle spectrograph with precision radial velocity (PRV) capability that will be a first light instrument for the Giant Magellan Telescope (GMT). G-CLEF has a PRV precision goal of 40 cm/sec (10 cm/s for multiple measurements) to enable detection of Earth-like exoplanets in the habitable zones of sun-like stars'. This precision is a primary driver of G-CLEF's structural design. Extreme stability is necessary to minimize image motions at the CCD detectors. Minute changes in temperature, pressure, and acceleration environments cause structural deformations, inducing image motions which degrade PRV precision. The instrument's structural design will ensure that the PRV goal is achieved under the environments G-CLEF will be subjected to as installed on the GMT azimuth platform, including: Millikelvin (0.001 K) thermal soaks and gradients 10 millibar changes in ambient pressure Changes in acceleration due to instrument tip/tilt and telescope slewing Carbon fiber/cyanate composite was selected for the optical bench structure in order to meet performance goals. Low coefficient of thermal expansion (C 1E) and high stiffness-to-weight are key features of the composite optical bench design. Manufacturability and serviceability of the instrument are also drivers of the design. In this paper, we discuss analyses leading to technical choices made to minimize G-CLEF's sensitivity to changing environments. Finite element analysis (FEA) and image motion sensitivity studies were conducted to determine PRV performance under operational environments. We discuss the design of the optical bench structure to optimize stiffness to -weight and minimize deformations due to inertial and pressure effects. We also discuss quasi-kinematic mounting of optical elements and assemblies, and optimization of these to ensure minimal image motion under thermal, pressure, and inertial loads expected during PRV observations.
    • Advances in modeling polarimeter performance

      Chipman, Russell A.; Univ Arizona, Coll Opt Sci (SPIE-INT SOC OPTICAL ENGINEERING, 2017-08-30)
      Artifacts in polarimeters are apparent polarization features which are not real but result from the systematic errors in the polarimeter. The polarization artifacts are different between division of focal plane, spectral, and time modulation polarimeters. Artifacts result from many sources such as source properties, micropolarizer arrays, coatings issues, vibrations, and stress birefringence. A modeling examples of polarization artifacts due to a micro-polarizer array polarimeter is presented.
    • AI and the transcendence of true autonomy

      Tarbell, Mark; Univ Arizona, Coll Engn, Visual & Autonomous Explorat Syst Res Lab (SPIE-INT SOC OPTICAL ENGINEERING, 2019-05-13)
      For more than sixty years, the "Holy Grail" of computer science has been to build an intelligent, autonomous system, one that is self-aware and capable of rational thought. The founders of Artificial Intelligence recently gave a grim assessment of their field: AI and neuroscience are fixated on the details of implementation, without a fundamental architecture in sight.(1) No one has ever articulated the design for an autonomous system, so how can one be built? Modern AI/AGI efforts attempt to achieve this goal through elaborate rules-based computation and biology-inspired computing topologies, while actively ignoring the need for a fundamental architecture. This publication introduces a novel architecture and fundamental operating theory behind true autonomy, breaking with the standard principles of AI the very principles that have kept AI from achieving its own goals.
    • Air lens vs aspheric surface: a lens design case study

      Gao, Weichuan; Sasian, Jose; Univ Arizona, Coll Opt Sci (SPIE-INT SOC OPTICAL ENGINEERING, 2017-11-27)
      We discuss the behavior of air lenses in lens design. The structural aberration coefficients of a thin air lens are derived and compared with their glass thin lens counterpart. Examples are provided for a telephoto lens and the Monochromatic Quartet where air lenses or aspheric surfaces are used.
    • Alignment of a three-mirror telescope using the sine condition test

      Sommitz, David; Dubin, Matthew; Univ Arizona, Coll Opt Sci (SPIE-INT SOC OPTICAL ENGINEERING, 2018)
      The Sine Condition Test has been experimentally demonstrated as an effective tool for measuring linearly field dependent aberrations in simple optical systems. Simulations have also shown that it can be used to provide feedback as part of an alignment procedure for more complex systems. In this paper we show how the Sine Condition Test was used as part of the process for aligning a three mirror telescope. We present the basic concept of the Sine Condition Test, how it was implemented in our system and the experimental results from multiple alignments. Finally, we compare our experimental results to simulated results.
    • Alignment of Multi-Order Diffractive Engineered (MODE) lens segments using the Kinematically-Engaged Yoke System

      Esparza, Marcos; Choi, Heejoo; Kim, Dae Wook; Univ Arizona, James C Wyant Coll Opt Sci; Univ Arizona, Dept Astron; Univ Arizona, Steward Observ (SPIE-INT SOC OPTICAL ENGINEERING, 2020-08-20)
      With the continued development of multi-order diffractive engineered (MODE) lenses that consist of both multi-order diffractive surfaces and a diffractive Fresnel lens surface, it is becoming more realistic that these components may be used as an ultralight large aperture primary for space telescopes. As conceptual designs for these large primaries push the size limits of optics manufactured by compression molding, it becomes necessary to make a segmented MODE lens primary rather than a monolithic one. We use the Kinematically-Engaged Yoke System (KEYS) to align the segments of a 0.24-m, PMMA, monochromatic, MODE-like lens (having no diffractive Fresnel lens features). The KEYS alignment system consists of modified ultra-fine alignment screws with ball bearings on the end that kinematically engage with the step-like features of the MODE lens surface (similar to a Fresnel lens) to constrain the segments in 5 degrees of freedom, leaving rotation about the optical axis unconstrained. The alignment of the segments is verified using multiple methods including a scanning white light interferometer and deflectometry. Such an alignment system has the capability of fixing the segments together in order to bond them with adhesive while aligned. These tests offer a proof of concept for a system that can be used for an eventual 0.24-m, compression molded, glass, segmented MODE lens.