Careers in Electro-Optics: An Aerospace Perspective

Electro-Optics (EO) for Aerospace Applications : 

Electro-Optics (EO) for Aerospace Applications Carl Tuttle, Ph.D. 01/21/2011 Disclaimer: Does NOT contain any information Classified as Secret / Proprietary / ITAR Controlled

Slide 2: 

Airborne Laser Testbed Wavefront Sensing System Credit: Lockheed Martin public web site (http://www.lockheedmartin.com/ssc/products.html)

Contents : 

Contents Overview and Terminology Applied Electro-Optics (EO) Areas of Technology Development Recent Research Examples Local and National Lines of Business Aerospace EO and Lockheed Martin Space Systems Fundamental EO Concepts and Applications Diffraction and Resolution Space Telescopes (HST, Spitzer, JWST) Exoplanet Detection Principles Starshade / Occulter Concept Interference and Coherence Astronomical Interferometry Nulling Interferometry Sparse / Distributed Apertures

Contents, ii : 

Contents, ii Fundamental EO Concepts and Examples (Cont.) Wavefront Aberration and Spatial Filtering Single-Mode Optical Fibers Fiber-Linked Interferometer Arrays Adaptive Optics Astronomical Wavefront Correction Adaptive Mirrors using MEMS Micro-mirror Arrays EO Case Studies for Aerospace Applications Coherent Fiber Array NASA Nulling Interferometer Integrated Optical Beam Launcher Picometer Heterodyne Metrology Airborne Laser Beam Control and Fire Control System Ballistic Missile Defense

Overview / Terminology : 

Overview / Terminology

Overview / Terminology : 

Overview / Terminology Photonics: Science describing generation, emission, transmission, modulation, switching, amplification, detection, and sensing of light across EM spectrum (typically UV – IR wavelengths) Electro-Optics (EO): Technology involving components, devices and systems designed to interact between optical and electronic states Note that the EO Effect specifically relates refractive index change to applied electric field (e.g. Pockels, Kerr Effect Devices) EO implies optical devices in which electronic effects play a role (e.g., lasers, optical switches, CCD cameras) EO also denotes imaging sensors used for surveillance by government / military and aerospace contractors

Overview / Terminology : 

Overview / Terminology Some Photonics / EO Milestones: Optical Maser / Laser (1958 / 1960) Laser diode (1962) Single-mode fibers developed for signal transmission (1970) Erbium Doped Fiber Amplifiers (1986) Periodically Poled LiNO3 for Optical Parametric Oscillator (1993) Blue LED developed (1993) Silicon laser integrated on photonic chip (2005) Photonics / EO established telecommunications revolution, providing electronic / optical infrastructure for the internet

Photonics / EO Includes Multiple Disciplines : 

Photonics / EO Includes Multiple Disciplines Classical Optics: Includes familiar refracting lenses, dispersive prisms & reflecting mirrors, described by ray-tracing; also includes wave properties of light and components like fiber optics and planar waveguide integrated optics, best described by EM modes Quantum Optics: Study of the nature, effects, and applications of light described by quantized photons; quantum and coherence properties of light and interaction between light and matter Nonlinear Optics: Describes light in nonlinear media, where superposition principle no longer holds, and material responds non-linearly to EM field of incident light; observed at very high intensities, such as from pulsed lasers Optoelectronics: Primarily electronic devices and systems which involve light; electronic devices to source, detect and control light; electrical / optical transducers (LED, LCD, CCD) Optomechanics: Manufacture and maintenance of optical parts and devices, production of precision optical parts; response of optical systems to temperature and stress

Slide 9: 

Optical (EM) SPECTRUM 10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 10 102 LASERS 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 10600 Ultraviolet Visible Near Infrared Far Infrared Gamma Rays X-Rays Ultra- Visible Infrared Micro- Radar TV Radio violet waves waves waves waves Wavelength (m) Wavelength (nm) Nd:YAG 1064 GaAs 905 HeNe 633 Ar 488/515 CO2 10600 XeCl 308 KrF 248 2w Nd:YAG 532 ArF 193 Communication Diode 1550 Ruby 694 Credit: Laser-Professionals.com Alexandrite 755

Slide 10: 

LASER COMPONENTS ACTIVE MEDIUM Solid (Crystal) Gas Semiconductor (Diode) Liquid (Dye) EXCITATION MECHANISM Optical Electrical Chemical OPTICAL RESONATOR HR Mirror and Output Coupler The Active Medium contains atoms which can emit light by stimulated emission. The Excitation Mechanism is a source of energy to excite the atoms to the proper energy state. The Optical Resonator reflects the laser beam through the active medium for amplification. Laser-Professionals.com

Ray, Wave, & Quantum Regimes : 

Ray, Wave, & Quantum Regimes Scalar Theory Vector Theory λ << D Photons Credit: Saleh & Teich, Fundamentals of Photonics (1991)

Classical Optics Components include Mirrors, Beamsplitters and Lenses : 

Classical Optics Components include Mirrors, Beamsplitters and Lenses Ray, Wave, and Quantum Regimes Rays and Waves Quantum States – Optical Lattice

Electro-Optics (EO) Applications : 

Electro-Optics (EO) Applications

EO Technology Areas : 

EO Technology Areas EO technologies are everywhere: Consumer Electronics: barcodes, printing, scanners, CD / DVD / Blu-ray devices, data storage, CCD Cameras Telecommunications: fiber optic transmission, optical switching, microwave converters Medicine: eye surgery, laser surgery, endoscopy, health monitoring Industrial / Manufacturing: laser welding, drilling, imprinting & cutting; interferometric inspection & surface measurements; surface modification, chemical synthesis Scientific Research: microscopes, spectrometers, bio-photonics Aviation: optical gyroscopes, displays, LIDAR/LADAR Military: IR sensors, rangefinders, target detection and ID, missile defense, satellite surveillance Metrology: time and frequency measurements, precision positioning of optical and mechanical components Photonic & Quantum computing: secure communications, communication between computers, optoelectronic integrated circuits Astronomy: Telescopes, Stellar and Nulling Interferometry, Coronagraphy, Adaptive Optics, Spectrometers, CCDs, photon-counting detectors Energy: Solar power, laser fusion

Example - Photonic Metamaterials : 

Example - Photonic Metamaterials Engineered photonic metamaterials exhibit EM properties not found in naturally occurring materials Some nanostructured materials have negative refractive index in visible spectrum Electric (E) & Magnetic (B) field components of light => use both E & B to control light propagation through objects Atoms in standard materials interact very weakly with magnetic fields oscillating at visible frequencies Engineered lattice of square, split, nano-ring resonators provides negative magnetic permeability Incident EM field drives alternating charges within nano-rings, generating small electromagnets that collectively interact with light B field Creates new possibilities for manipulating light Superlens Negative index metamaterials exceed diffraction limit by compensating for diffracted wave oscillations Cloaking Device Stealth technology intended to make invisible objects over parts of EM spectrum, Metamaterials bend light around object surfaces

Example - Photonic Crystals : 

Augustin, et al., Opt. Expr., 2003 Borel, et. al., Opt. Expr. (2004) guiding light with extreme bends Example - Photonic Crystals Photonic Crystals (PC) are made of periodic internal regions of high and low dielectric constant that affect light propagation similar to periodic potential in semiconductors defining allowed and forbidden electronic energy bands Light waves may propagate through PC structure depending on wavelength Allowed wavelengths are modes, and groups of allowed modes form bands; disallowed bands are called photonic band gaps Photonic crystal fibers can guide light with higher power levels, lower loss and at wavelengths not possible with conventional fiber optics

Example: Photonic Chips for Telecom : 

Example: Photonic Chips for Telecom V-Groove assembly for aligning polarization-maintaining fibers & coupling light to photonic chip Also Called: Integrated Optics Photonic Integrated Circuits (PIC) Photonic Lightwave Circuits (PLC)

Example: Next Generation Telecom Chips : 

Example: Next Generation Telecom Chips

Bay Area EO Scientific & Business Interests : 

Bay Area EO Scientific & Business Interests Astronomical Optics & Research: NASA Ames (Ames Coronagraph Experiment Laboratory), UC Santa Cruz (Center / Lab for Adaptive Optics), Lick Observatory, Lockheed Martin Advanced Technology Center, etc. Basic Optics & Photonics Research: UC Berkeley (XLab), Stanford (Edward Ginzton Laboratory), SRI (Applied Optics Laboratory), SLAC (SLS), UC Santa Cruz (Applied Optics Group), SJSU, etc. Consumer Optics / Imaging Devices: Agilent, AI Vision, Applied Materials, Better Light, Fairchild Imaging, Flextronics, I-Chips Technology, Intevac, OmniVision, PerkinElmer Optoelectronics, RGB Spectrum, etc. Energy Research: LLNL NIF, SolFocus, SunPower, etc. Lasers / Light Sources: Advanced Radiation, Applied Photon Technology, Coherent, Conex Systems, Continuum, DPSS, Spectra-Physics, etc. Medical Optics: Accuray, Acuson, APS Optics, Carl Zeiss Meditec, Intuitive Surgical, TTI Medical, Agilent / Varian, etc. Metrology / Optical Instrumentation: HP-Agilent, DataRay, Micro-Vu, etc. Optical Systems for Semiconductor Manufacturing & Testing: Axic, Intel, KLA-Tencor, Lam Research, National Semiconductor, etc. Optical Systems for Aerospace & Defense: NASA Ames, Lockheed Martin Space Systems, etc. Optics & Optomechanics Component Manufacturing: Newport, New Focus, Argus, Dominar, Griot Group, MLD Technologies, Tinsley Optics, etc. Telecommunications & Fiber Optics: Alcatel, Aerotech, Alliance, Avanex, Cisco, Fibersense, Finisar, General Photonics, Infinera, JDS Uniphase, etc.

United States Electro-Optics Companies : 

United States Electro-Optics Companies

Aerospace EO / Lockheed Martin : 

Aerospace EO / Lockheed Martin Lockheed Martin (NYSE: LMT) is a US aerospace, defense, security, and technology company with worldwide interests, employing ~140,000 people, 2009 sales of ~$45B LM is among largest defense contractors worldwide; 70% of revenues came from military sales (2008 data) LM Companies: LM Aeronautics LM Electronic Systems LM Information Systems & Global Solutions LM Space Systems: includes space launch vehicles, commercial satellites, government satellites, strategic missiles, and ballistic missile defense lines of business Lockheed Martin Space Systems (LMSS) (Denver, CO) Lockheed Martin Missiles & Space Organization (Sunnyvale, CA) Lockheed Martin Advanced Technology Center (Palo Alto, CA) Denver, Sunnyvale, Palo Alto facilities employ ~4000, ~8000, ~700

Space Based Infrared System (SBIRS) : 

LM is prime contractor and systems integrator for SBIRS High / GEO program, a next-generation infrared-sensing missile warning system also providing reconnaissance capability SBIRS constellation: 2 satellites in highly elliptical orbit, 4 satellites in geosynchronous orbit, and ground stations to receive & process data Primary mirror precision reflectometer Testing: Northrop Grumman, Azusa, CA Space Based Infrared System (SBIRS) Photo Credits: Lockheed Martin Web Site

SBIRS Thermal-Vacuum Testing : 

SBIRS Thermal-Vacuum Testing Photo Credits: Lockheed Martin

EO Concepts / Examples : 

EO Concepts / Examples

Diffraction and Interference : 

Diffraction and Interference Fundamental wave property of light When an aperture or object is placed between observing screen and source, interference produces bright and dark regions not predicted by ray optics. Diffraction is an interference phenomenon Defined as any deviation of light rays from linear paths that cannot be interpreted as reflection or refraction Customary to refer to interference as the superposition of a few discrete waves, and diffraction when discussing the superposition of a large number or continuum of waves

Slide 26: 

Light from a source incident on a circular aperture interferes constructively and destructively in the image plane to form a pattern of light and dark Airy rings Diffraction-Limited Angular Resolution Airy rings of two point sources overlapping Θmin= 1.22 (λ / D) Airy pattern or PSF of point source (star) Rayleigh Criterion: two monochromatic point sources can be resolved if the central peaks have an angular separation greater than the first null of the Airy function q D Point object NOTES: Diffraction limited telescopes degraded by optical aberrations & seeing effects from atmospheric turbulence Mitigated by locating telescope at high altitude, adaptive optics, or placing telescopes in space

Hubble Space Telescope (HST) : 

Hubble Space Telescope (HST) Omega Centauri - WFC3 Photo Credits: NASA Visible to Near-IR Let λ ~ 0.6 µm Θm~ (λ / D) ~ 0.6e-6 / 2.4 / 4.9e-6 ~ 0.05 arc-seconds (50 milliarcseconds) Only true without Atmospheric effects

SPITZER SPACE TELESCOPE : 

SPITZER SPACE TELESCOPE Infrared (IR) radiation from proto-planetary systems and galactic cores is mostly absorbed by Earth’s atmosphere Cryogenically-cooled, high sensitivity space observatory for IR astronomy ~ 1 m telescope and 3 scientific instruments for imaging & spectroscopy from 3 – 180 um Uses large-format IR detector array; provides 100-fold greater capability over previous missions * Credit: Lockheed Martin Photo Credits: NASA

James Webb Space Telescope (JWST) : 

James Webb Space Telescope (JWST) Illustration Credit: NASA

JWST - NIRCAM : 

JWST - NIRCAM NIRCam Optics NIRCAM Instruments (2 shown) 6.5-m JWST Primary Mirror LMSS / ATC is constructing Near Infrared Camera (NIRCam), the principal science instrument aboard the JWST). Building and delivering an IR flight imaging system that works well over a large spectrum (0.6 to 5.0 microns), under hard cryogenic conditions (35 Kelvin), presents significant design challenges Diagram Credits: Lockheed Martin

Detection of Habitable Exoplanets : 

Detection of Habitable Exoplanets Gliese 581 exoplanetary system has potentially habitable candidate Host star is M3 red dwarf 20 light years away Orbiting star are 6 planets; foreground planet is GJ 581g, circling star in habitable zone (liquid water can exist) One side of GJ 581g always faces star (perpetual day); terminator region may have temperatures 50-100 F mass and diameter predict surface gravity similar to Earth, allowing the planet to retain an atmosphere Picture Credit: NASA

Detection of Habitable Exoplanets : 

Detection of Habitable Exoplanets TPF: search closest stars to detect planets & life signs (biomarkers) Habitable planets Mass between 0.5 - 10 times M(earth) Stellar distance so surface temperature & pressure allow for liquid water For visible & near IR, prefer 0.7 - 1.0 μm band: O2 Spectral lines ~ 0.70 μm Require 10-10 starlight suppression level in visible band (extreme contrast ratio) • Visible (0.7 microns) –Earth / Sun ~ 10-10 –Zodiacal emission small • Infrared (10 microns) –Earth / Sun ~ 10-7 –Zodiacal emission large From J. Kasdin, NASA Ames Talk, 2010 Contrast Ratio ~ 10-10

Detection of Habitable Exoplanets : 

Detection of Habitable Exoplanets Credit: J. Kasdin, NASA Ames Presentation, 2010

Starshade / Occulter : 

Starshade / Occulter In space, atmospheric wavefront distortion is removed, but telescope diffraction and scattered light remain Proposed approaches require highly demanding optical wavefront control Alternative: use occulting starshield to block unwanted starlight Compact coronagraph mission design traded for two spacecraft complexity Wavefront challenge replaced with precision deployable ~30 m sheet Fly occulter in formation with >1 m telescope, to detect terrestrial exoplanets up to 10 Pc away Proposed mission Theia / XPC LMSS designed occulter spacecraft Occulter positioned to block starlight with telescope in shadow Telescope sees occulter outlined against residual star light Small amount of starlight diffracts around shade petals Planets seen as faint objects in image field of view Picture Credit: Cash, et. al. (2006)

Starshade / Occulter : 

Starshade / Occulter Integration of the Fresnel diffraction equations gives apodization functions that yield greatly reduced diffraction Detecting planet 0.1 arcsec from star in visible band requires occulter of radius R > 20 m located at distance F > 40,000 km from telescope Kasdin, N. J., Vanderbei, R. J., e. al., “Extrasolar planet finding via optimal apodized and shaped pupil coronagraphs”, Ap. J. 582 (2003) Vanderbei, R. J., Spergel, et. al., “Circularly symmetric apodization via star-shaped masks”, Ap. J. 599 (2003) Cash, W., “Detection of Earth-like planets around nearby stars using a petal-shaped occulter”, Nature 442 (2006) Picture Credits: Lockheed Martin

Interference and Coherence : 

Interference and Coherence Consider monochromatic (single frequency) light first (lasers) Combine waves to form composite wave, described as a vector sum of waves in space & time (Superposition principle) When combining waves, must include light Direction, Polarization, Amplitude, Frequency & Phase Constructive or destructive interference depends on phase shift between waves Coherence is required for interference: constant phase relation between beams + = Constructive Interference (In phase) + = ( p out of phase) (Waves cancel) Destructive interference

Temporal and Spatial Coherence : 

Temporal and Spatial Coherence Statistical property of EM fields A light field is coherent if there exists a fixed phase relationship between the EM field values at different locations and times Spatial coherence is a phase correlation between EM fields at one time and different locations on the plane transverse to beam propagation direction, depending on wavefront spatial uniformity Temporal coherence is phase correlation between EM fields at one location and different times along longitudinal beam, depends on spectral width Coherence time is reciprocal of the bandwidth: Lasers with narrow spectral line width have high temporal and spatial coherence, and transverse EM fields have highly correlated oscillations, resulting in strong beam directionality Thermal light sources have multiple wavelengths & randomly varying phases that interfere only over very short distances: elsewhere beams combine according to scalar intensity addition Ideal Laser Single Phase Gaussian Spatial Laser Mode Single Frequency Beam

Astronomical Interferometry : 

Astronomical Interferometry Single telescope resolution limited by diffraction & atmosphere Largest telescopes have D ~ 10 m and  ~ 0.1” with ideal seeing Large aperture D gains in light-collecting power but not resolution Mitigate atmosphere with adaptive optics and image post-processing Astronomical interferometers coherently combine light from N ≥ 2 telescopes, producing visible or temporal interference fringes which determine object scale in the baseline direction Baseline telescope separation gives resolution limit: Baselines B = 100 m result in  ~ 0.001” (1 mas) in visible Light collecting power limited by individual aperture size Imaging performance limited by discrete baseline sampling Spatial incoherence across and between apertures created by atmospheric turbulence Reduces fringe visibility for large telescopes Solutions: small telescopes, adaptive optics, spatial filtering

Optical Atronomical Interferometry : 

Optical Atronomical Interferometry Geometry of 2-Telescope Astronomical Interferometer

Interferometric Fringe Visibility : 

Interferometric Fringe Visibility Fringe phase Φ shifted relative to phase centre Van Cittert-Zernike theorem: Phase Intensity I: Source intensity s: Source direction b: Baseline Projected components of source spatial intensity distribution on the sky are related to the complex fringe visibility function by Fourier transform

Ground-based Interferometers: Keck I + II : 

Ground-based Interferometers: Keck I + II Two 10 m mirrors each with 36 hexagonal 1-m actively aligned segments Single telescope optical resolution ~ 0.05 arcsec (K Band, 2.2 um) using adaptive optics system As an interferometer, angular resolution of an 85 m telescope: Δθ ~ λ / B = ~0.005 arcsec NASA Origins studies: astrometry, protoplanetary disks, exoplanet candidates Picture Credits: Keck Observatory

Nulling Interferometry Principles : 

Nulling Interferometry Principles Combine beams 180o out of phase at zero path difference Null depth is ratio of transmitted power of starlight to planet light Combine light from multiple telescopes; output image Airy function modulated by fringe pattern on sky with spacing Δθ~ λ/B Starlight within null is blocked; planet light at fringe peak is transmitted to detector Monochromatic light relatively easy, difficult over a finite bandwidth Imperfect optics scatter light, reducing the null depth For Earth-Sun system at 10 pc, Earth-Sun separation is 0.1 arcsec & required fringe spacing is λ/B = 0.2 arcsec At 0.6 micron wavelength, desired baseline is B ~ 0.6 m, smaller than telescope diameter needed for Earth detection How do we get nulling interference from a single telescope? See VINCO example below for answer

Slide 43: 

Nulling Interferometry for Exoplanet Detection planet star Interferometric Fringe Pattern Mirror CCD Telescope #1 Telescope #2 π/2 Phase Delay Mirror Beam Splitter Transmission Pattern of Nuller on sky (star is at center) l/B l/2B Baseline, B “Nulling Interferometry for Spectroscopic Investigation of Exoplanets - A Statistical Analysis of Imperfections”, Oswald Wallnera, Klaus Kudielkab, et. al., SPIE Vol. 4273 (2001)

Sparse / Distributed Aperture Telescopes : 

Sparse / Distributed Aperture Telescopes Sparse Aperture Telescope Optics Sparse aperture approach uses multiple small telescopes to synthesize larger effective aperture Advantages: Reduced size, weight and cost of system Star-9 Telescope Test Bed Nine small phased telescopes synthesize a ~ 1 m effective aperture Measured resolution is nearly diffraction limited Use image restoration techniques to remove effect of discrete apertures Image Credits: Lockheed Martin

Wavefront Aberration & Spatial Filtering : 

Wavefront Aberration & Spatial Filtering From J. Kasdin, NASA Ames, 2010

Wavefront Aberration & Spatial Filtering : 

Wavefront Aberration & Spatial Filtering Aperture (Pupil Function) Image (Airy Function) (1) J. Kasdin, NASA Ames Talk, 2010 (2) Optical methods of engineering analysis  G. L. Cloud (1998) Notes: Filtering imperfect; High throughput losses (2) (1)

Optical Fiber Waveguides : 

Optical Fiber Waveguides Critical angle (θc) Maximum allowed angle within fiber for total internal guiding Numerical Aperture (NA) larger NA => fiber will accept greater amount of externally coupled light Acceptance Angle (θa) Maximum angle to couple to fiber

Single-Mode (SM) Optical Fibers : 

Single-Mode (SM) Optical Fibers Wave description yields stable propagation states: fiber modes single mode (only one path for light waves down the fiber) multimode (many higher order path waves down the fiber) V-Parameter quantifies allowed fiber modes Single-mode if V < 2.405 Single mode described by single field amplitude and phase Single Mode (SM)

Fiber-Linked Interferometer Array : 

Fiber-Linked Interferometer Array SM Fibers: perfect spatial filters (actually modal filters) Eliminate amplitude & phase errors from coupled beams Near lossless transport of light Perfect wave coupling = 80% Wavefront errors decrease coupling Must compensate for fiber dispersion, polarization, path length corrections, etc. Best used with low-order adaptive optics system SM Fiber Field Profile

Adaptive Optics (AO) for Wavefront Correction : 

Adaptive Optics (AO) for Wavefront Correction Under ideal circumstances resolution is only limited by diffraction (ΔΘ = 1.22 λ/ D) In practice limit cannot be reached due to Earth's atmosphere and surface figure imperfections in the optics Atmospheric blurring and wavefront distortion can be mitigated Deploying telescope in space Using small apertures or spatial filters Using Adaptive Optics (AO) AO advantages: Faint objects can be imaged over long exposures Interferometric observations improved by removing random delay, tilt, and higher order aberrations from telescopes prior to beam combination AO operation: Bright reference source is used to determine distorted wavefront shape Light from source is analyzed by wavefront sensor Actuators change surface of small mirrors following sensor commands Shape of mirrors is updated at up to kilohertz rates

Adaptive Optics: Laser Guide Stars : 

Adaptive Optics: Laser Guide Stars AO works only if reference star is BRIGHT & CLOSE to science object Use Artificial Sodium Laser Guide Star Keck II Laser Guide Star Lick Laser Guide Star *

Diagram of AO System : 

Diagram of AO System Starburst galaxy NGC7469. Canada-France-Hawaii Telescope

Adaptive Optics: Wavefront Sensors : 

Adaptive Optics: Wavefront Sensors f Principle of Shack-Hartman Wavefront Sensor Analyze Sub-Aperture Spot Centroids to Estimate Wavefront Spot Displacement (Δx, Δy) indicates local error

Slide 54: 

Electronic driver array and control computer Adaptive Optics: MEMS DMs Picture Credits: Lockheed Martin and BMM LM MEMS adaptive optics test bed uses the MEMS device at left

Adaptive Optics: MEMS DM : 

Fabrication Silicon MEMS devices made using IC fabrication techniques by Boston Micromachines Actuation Electrostatic parallel plates, individual actuator addressing Configuration 32 x 32 element square array (1024 actuators) 64 x 64 array (4096 actuators) in development Optical Quality 98% Fill Factor, 90% Reflectance (gold), 12nm RMS pixel flatness Adaptive Optics: MEMS DM contour map of deflected pixel Image Credits: NASA-JPL

Coherent Fiber Array for NASA Nulling Interferometer : 

Coherent Fiber Array for NASA Nulling Interferometer Credits for VINCO slides: Mike Shao, Marty Levine, et. al., NASA/JPL Credits for fiber array slides: Duncan Liu, Francisco Aguayo, et. al., NASA/JPL

Coherent Fiber Array for NASA Nulling Interferometer : 

Coherent Fiber Array for NASA Nulling Interferometer Goal: Direct detection and imaging of exoplanets around nearby stars Direct detection possible at 2 bands: visible & thermal IR (10 microns) IR: Nulling interferometer with long baseline ~20 m, large apertures Visible: Required resolution achieved with large single aperture A Visible Nulling Coronagraph (VINCO) combines advantages of the nulling interferometer and coronagraph-type telescope designs Can equal sensitivity of Lyot coronagraph with 2X smaller aperture & lower optical quality requirement VINCO instrument placed between telescope and CCD detector Suppresses starlight by ~1010 (using l/20 P-V optics, adaptive correction, and single mode fibers for spatial filtering) JPL has vacuum testbed for deep, stable, broadband cancellation, improved vibration stabilization, phase, intensity & polarization control Achieved 1000000:1 white-light null depth, 15% band (Samuele, Wallace, et. al. , JPL Tech. Pubs., 2007)

Visible Nulling Coronagraph (VINCO) : 

Visible Nulling Coronagraph (VINCO) Image of Solar System Simulation of 4m nulling interferometer (60 cm shear) image after rotation Solar system at 10pc SNR=5 on Earth in 2.5 hrs Credit: Shao, Serabyn, et. Al., AAS (2003)

VINCO: Modified Mach-Zehnder Interferometer : 

VINCO: Modified Mach-Zehnder Interferometer Dispersive Components For Achromatic Nulls Variable delay Variable Shear Null Output Bright Output Shear One of two shearing stages Required in X & Y directions

VINCO Concept : 

VINCO Concept Y shear MMZ Telescope Pupil q4 Null in Pupil Overlap Area - + Diffraction limited imaging system (l/15) Lenslet and fiber-optic array spatial filter s s = + - X shear MMZ Beam with In-line shear, q4 null output Relay Mirrors Image plane (real image) ~(64 x 64)

Coherent Fiber Array (CFA) : 

Coherent Fiber Array (CFA) SM fibers spatially filter wavefront errors to reduce scattered light Require ~1000 fiber array for FOV & required scattering reduction Use low-NA fibers for improved coupling MEMS DM corrects low-order aberrations & fiber alignment errors Currently can make ~500 fiber arrays (Shao, Clampin, et. al., 2010) Fibers arranged between polished glass prisms with UV-cured epoxy Polish lengths to ~λ/10 to maintain diffraction-limited image quality Lenslet arrays matching fiber spacing couple light in & out of fiber array Utilize custom-etched lenslets to match fiber positional variations Lenslet arrays bonded to fiber array using index-matching epoxy

Slide 62: 

RMS WFE for Adjacent Lenslets (Exclude Boundaries, 80% Clear Aperture): 0.054 Waves Coherent Fiber Array (CFA) Liu, Levine, et. al., JPL Tech Pub (2006) Distorted Wavefront Filtered Wavefront

CFA with Adaptive Optics : 

CFA with Adaptive Optics

Slide 64: 

Polished end of the 496 fiber array with RMS fiber placement error of 2.78um Reference mask made with e-beam photolithography Light output of large core 496 fiber array with coupling via lens array Precision polished prisms for making fiber array Coherent Fiber Array (CFA) Credits: Liu, Levine, et. al., JPL Tech. Pubs (2006)

Precision Custom Micro-Lenslet Array : 

Vitrum MICRO-LENSLET ARRAY (MLA) Array Size: 200 x 200 Lenslet Diameter: 126 microns Lenslet Focal Length: 2.4145 mm (glass) F/number: 19.16 Lens Material: Epoxy Substrate Material: Fused Silica Substrate Thickness: 2.286 mm Defocus Error: 0.1285 mm Focus Depth, 633nm: 1.13 mm Pinhole Diameter: 15 microns Precision Custom Micro-Lenslet Array

Integrated Optical Beam Launcher for Picometer Heterodyne Metrology : 

Integrated Optical Beam Launcher for Picometer Heterodyne Metrology

Planar & Cylindrical Waveguides : 

Planar & Cylindrical Waveguides Credits: Saleh & Teich, “Fundamentals of Photonics” (1991) Design planar Waveguide for Single-Mode Propagation

Waveguides: Planar / Rectangular : 

Waveguides: Planar / Rectangular Credits: Saleh & Teich, “Fundamentals of Photonics” (1991)

Waveguides: Planar / Rectangular : 

Waveguides: Planar / Rectangular Directional or 3 dB coupler: Design so that light is split evenly b/w guides; uses waveguide evanescent field coupling EO switch and Mach-Zehnder intensity modulator; applied field changes phase of beam in waveguide channels to control output intensity Credits: Saleh & Teich, “Fundamentals of Photonics” (1991)

Planar Waveguides for Astronomical Interferometry : 

Planar Waveguides for Astronomical Interferometry Planar Waveguide used as interferometer beam combiner and spatial filter Credits: J. P. Berger, P. Kern, F. Malbet, R. Millan-Gabet, W. Traub, etal., HSCFA, IOTA

Photonic Circuit Modeling : 

Photonic Circuit Modeling Optiwave (Canada): Beam Propagation Method (BPM): computational technique in Electromagnetics, used to solve the Helmholtz equation for time-harmonic waves Photon Design (UK): Waveguide mode solvers: finite-difference and finite-element methods Vectorial and bi-directional propagation method based on EigenMode Expansion

Integrated Beam Launcher: Precision Metrology : 

Integrated Beam Launcher: Precision Metrology Advanced optical systems, especially involving optical interferometric combination, such as the NASA Terrestrial Planet Finder (TPF), require knowledge of relative positions of optical components to sub-nanometer or picometer level accuracy

Optical Metrology Gauges : 

Optical Metrology Gauges Measure relative distance change between two fiducial points Fiducials are retro-reflecting devices (e.g., corner cubes) Measurement laser beam traveling to and from fiducial points is combined with reference beam to generate electronic heterodyne beat note signal Heterodyne output signal phase is measured and tracked (counted) 360 degrees =1 wavelength of distance change Fringe tracking allows determining very long relative distance changes Consists of laser source, optical launcher, signal processing Precision regimes 1/1000 wave: alignment & control for single telescopes & industrial processes (microlithography, machining) 1/1000000 wave: astronomical optical interferometry Optical gauges of type (1) have been produced by Agilent (HP) and other companies since 1970s HeNe laser with magnetic field applied to Zeeman split laser mode into two orthogonally polarized components with frequencies (f, f+∆) Various launchers and signal processing options Machine shop use; Temperature and pressure sensing HP Displacement Measurement Precision: ~ 0.2 nm

Heterodyne Metrology : 

Dual-frequency laser input (f1 & f2), with f1 - f2 << fc = 1550 nm; Δf ~ 2 MHz; f1 & f2 have orthogonal polarizations Input split into measurement & reference beams by Polarizing Beam Splitter (PBS) Measurement beam f1 travels to reflecting target moving with velocityV, gaining Doppler shift Δf = 2V/λ1 over time t Measurement beam returns from target and combines on detector with alternate frequency reference beam (using a 45º polarizer plate) to obtain electronic beat signal with frequency |f1 - f2|+ Δf Subtract reference frequency |f1 - f2| to get Δf Doppler component Δf gives change in target baseline length ΔL = Vt = Δf λ1 t / 2 Heterodyne Metrology

Slide 75: 

Integrated Beam Launcher Description Components: laser source (1550 nm), acousto-optic frequency-shifters, optical chip, detectors, electronics Light delivery, propagation, mixing entirely performed using planar waveguide / single-mode fiber components Free-space optics gauges sensitive to vibrations, thermal expansion, polarization errors, alignment errors Avoids heavy, complex optics, orbital alignment Integrated devices insensitive to vibration, may be thermally stabilized Low power draw & dissipation, efficient packaging Requires space qualification Precision: ~100 picometers Integrated Beam Launcher: Precision Metrology

Slide 76: 

Integrated Beam Launcher: Precision Metrology

Integrated Beam Launcher: Precision Metrology : 

Integrated Beam Launcher: Precision Metrology Integrated-optical, miniaturized gauge to replace bulk-optic discrete gauge with many separate elements Integrated approach yields cost, size, weight & risk advantages over conventional approach Integrated Gauge Conventional Gauge

Airborne Laser Beam Control / Fire Control System for Ballistic Missile Defense : 

Airborne Laser Beam Control / Fire Control System for Ballistic Missile Defense

Airborne Laser Test Bed Program (ABL) : 

Airborne Laser Test Bed Program (ABL) USAF Missile Defense Agency Megawatt laser with highly modified 747 aircraft to acquire, track, and kill ballistic missiles in boost phase Main contractors Boeing: Systems integration, modified 747 & Battle Management Northrop Grumman: High Energy Laser (HEL) & Beacon Illuminator Lockheed Martin: Beam Control / Fire Control System (BC/FC) BC/FC System Tracks target, determines range, compensates for atmospheric turbulence, focuses & directs HEL HEL beam directed by BC/FC internal optics to exit conformal window on the aircraft ball turret Picture Credits: Boeing Corp.

Airborne Laser Test Bed Program (ABL) : 

Airborne Laser Test Bed Program (ABL) ABL Ball Turret with Conformal Window, Primary & Secondary Mirrors Visible Picture Credit: Boeing Corp.

ABL Engagement Sequence : 

ABL 0176R1 ABL Engagement Sequence Detect Acquire and track Six infrared search and track (IRST) seekers 360o passive plume detection capability Active laser provides range Off-the-shelf technology Fine track with TILL (track illuminator) Chemical-oxygen iodine laser (COIL) demonstrates required power and efficiency Kill mechanisms understood Scaled laser lethality tests against representative targets Compensate for atmosphere Compensate atmosphere with BILL (beacon illuminator laser) Kill Laser Deformable mirrors correct outgoing beam for optical turbulence Cleared for Public Release 12/17/03 AFRL/DE 23-608

ABL COIL Laser : 

ABL COIL Laser The chemical oxygen-iodine laser (COIL) is a short wavelength, high-power chemical laser Works by mixing hazardous chemicals including hydrogen peroxide, chlorine and iodine Lases with atomic iodine transition at 1.315 microns. The hot mixture of gases expands supersonically in a nozzle

ABL Beam Control : 

ABL Beam Control Picture Credit: Boeing Corp.

ABL Optical Inspection System : 

ABL Optical Inspection System Optical components and coatings are often damaged by HEL: During laser beam operation Failure to perform after varying periods of use Failure of optical coatings often caused by contamination on optics To improve reliability of ABL system and minimize incidence of unanticipated system failures, optics health monitoring is needed Optical Inspection System (OIS) CCD cameras Data acquisition hardware and software Illumination source Inspection Monitoring Requirements Contamination Monitoring Cleanliness Levels Detect particles > 100 µm diameter Size limits are dependent on the optic ABL Non-Flight Optic showing Particle Contamination

Slide 85: 

ABL Optical Inspection System Armor Jacketed SM Fiber Ground Cart for High-Power IR Illumination Laser Injection Launch Laser Illumination Beam to BCFC Optics Camera Control Unit & Laptop Interface Flight Fiber Optic Connection Point Inspection Beam Flight BC/FC Optics With Contamination OIS Operated on Ground Before / After HEL Firing

Current ABL Status : 

Current ABL Status EDWARDS AIR FORCE BASE, Calif., February 12th, 2010 -- Lockheed Martin (NYSE: LMT) announced today that the Beam Control/Fire Control system for the U.S. Missile Defense Agency’s Airborne Laser Testbed successfully aimed the High Energy Laser in an experiment on 2/11/2010, destroying a boosting ballistic missile target In the lethal demonstration, the directed energy system aboard the modified Boeing 747-400F aircraft engaged and destroyed the threat-representative ballistic missile target shortly after it was launched from a sea-based platform in the Pacific Ocean “The Beam Control/Fire Control (BC/FC) System has performed with outstanding results in the most demanding mission to date,” said Mark Johnson, ABL program director, LMSS “The BC/FC system, consisting of a sophisticated suite of optics, low-energy lasers and software, has been rigorously tested in more than 140 flights since 2004, making technology history all along the way as a result the close partnership and dedication of the government and industry team.” Additional aircraft cancelled by congress, ABL remains technology demonstration program

Slide 87: 

THANK YOU!

Backup Slides : 

Backup Slides

Quantum Optics : 

Quantum Optics Following work of Dirac in quantum field theory, Sudarshan, Glauber, & Mandel applied quantum theory to EM field to gain detailed understanding of photodetection and statistics of light Introduction of coherent state as quantum description of laser light and optical states beyond classical waves (e.g. squeezed states) Development of ultra-short laser pulses from Q-switching and mode-locking techniques Solid state applications (e.g. Raman spectroscopy) discovered; studies of forces induced by light on matter led to levitating and positioning clouds of atoms in optical traps with laser beams Optical tweezers and Doppler cooling were crucial developments required to realize Bose-Einstein condensation Other remarkable results include demonstration of quantum entanglement, quantum teleportation, quantum logic gates, quantum information research, manipulation of single atoms

Nonlinear Optics : 

Nonlinear Optics Frequency mixing processes Frequency doubling or second-harmonic generation: 1064 nm Nd:YAG or 800 nm Ti:sapphire laser output is converted to 532 nm or 400 nm visible light, using a strongly birefringent crystal Optical parametric amplification (OPA), amplification of a signal input in the presence of a higher-frequency pump wave, also generates idler wave Optical parametric oscillation (OPO), generating a signal and idler wave with a parametric amplifier in a resonator Optical parametric generation (OPG), like parametric oscillation but without resonator, uses very high gain Brillouin scattering: photon / acoustic phonon interaction Kerr effect: Refractive index changes with |E|2 Two-photon absorption: simultaneous absorption of two photons, transferring energy to a single electron

Electro-Optical Effect : 

Electro-Optical Effect Certain electro-optical materials with refractive index n change optical properties under E-field n  E : linear EO effect or Pockels effect n  E 2: quadratic EO effect or Kerr effect n very small; phase shift φ (0<n•d <2) n (E ) varies slightly => Taylor expansion Define coefficients: r and s (EO coefficients) Pockels Effect: materials with negligible s term Pockels coefficient r Typical value of r (1-100 pm/V) Common Pockels cell crystal: LiNbO3 Kerr Effect: center-symmetric material, n (E ) is even function => r = 0 Kerr coefficient s

Slide 92: 

Phase Modulator: Beam traverses Pockels cell of length L; field E applied to cell => phase shift 0  V V : half-wave voltage; depends on materials (n and r), wavelength, and geometry (d/L) Phase modulation Intensity Modulator / Switch: Use phase modulator in Mach-Zehnder interferometer  = (1-2): phase difference of branches 1 2

Slide 93: 

Directional Coupler: Control the coupling of light between two parallel single-mode planar waveguides  = 0 => power transfer distance L0  controlled by applied voltage Maximum T: L0 = 0; at L0 = 31/2, all optical power is transferred E = V/d for one waveguide and -V/d for another waveguide => The necessary switching voltage (V0) is set for L0 = 31/2

Slide 97: 

Bias to overcome 2-photon absorption