Multi-Spectral Transparent Materials Technologies - The American ...

American Ceramic Society – Baltimore, June 2010
Multi-Spectral
Transparent Materials Technologies
Daniel C. Harris
Naval Air Systems Command
China Lake, California
Daniel.Harris@navy.mil
760-939-1649
Multispectral ZnS was discovered by
Chuck Willingham at Raytheon in 1980
1

UV Visible Near IR
Atmospheric Transmission
Microwave
2

Magnesium Fluoride Dome on Sidewinder Missile Protects
Delicate Seeker and Transmits Infrared Radiation
MgF 2 dome
3

Lockheed Martin SNIPER Targeting Pod
Sapphire
window
SNIPER Pod
4

LANTIRN Zinc Sulfide Infrared Window
Lockheed
Martin photos
Joint Strike Fighter Electro-Optic Targeting System
Faceted Sapphire Window
ATFLIR
Zinc
Sulfide
window
Goodrich
photo
5

Germanium
window
Germanium Windows on SLAM-ER
6

Generic Issues for Window and Dome Materials
•
•
•
Transmission and emission at desired frequencies
Resistance to rain and sand erosion
Resistance to thermal shock
Electromagnetic shielding
Common External Window Materials
•
Long Wave Infrared (8-12 μm)
• Zinc sulfide (Dow, II-VI)
Germanium (Umicore)
•
Midwave Infrared (3-5 μm)
• Sapphire (Crystal Systems, Saint Gobain, Rubicon)
• Silicon
• Magnesium fluoride (France–Saint Gobain)
• Spinel (TA&T [Armorline], Surmet, MER)
ALON (aluminum oxynitride) (Surmet)
•
Visible and Near Infrared
• Various glasses
• Fused silica
7

Early Maverick Dome (ZnS) Broken by Rain Impact in 1980s
8

Sidewinder Dome (MgF 2 ) Pitted by Sand in Persian Gulf (1990)
9

Splat!
Bug Impact on ZnS/ZnSe Sandwich Window
[N. Osborne, University of Dayton Research Institute] 10

Dust Storm Created by Helicopter
[Aviation Week & Space Technology, 5 May 2008, page 34] 11

Candidate Midwave (3-5 μm) Materials
for High-Speed Systems
Optical GaP, yttria, and lanthana-doped yttria are not commercially available
12

Transmittance
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
“2-Color” (Midwave + Long Wave) Materials
0
ms-ZnS
Ge
2 4 6 8 10 12 14 16
•Ge – Great for aircraft. Operating
temperature up to ~100°C
•Si – Only midwave. Operating
temperature up to ~250°C
•GaP – Midwave, not long wave.
Operating temperature up to
~600°C (Mach 4). High dn/dT.
Poor erosion resistance. Not
commercially available.
GaP
Si
3-5 μm 8-14 μm
Wavelength (μm)
GaAs
ZnSe
•GaAs – Excellent optical quality in both
bands. Operating temperature up to
~400°C (Mach 3). Erosion resistance is
modest. Not commercially available.
• ZnSe – Superb optical quality in both bands,
but very poor erosion resistance
• Multispectral ZnS – The only contender for
Mach 4. Poor erosion resistance could
be improved by coatings
13

II-VI, Inc.
High Quality Zinc Sulfide is Grown in Large Areas
by Chemical Vapor Deposition
14

There is no adequate erosion
protection coating for zinc sulfide
There is no durable multispectral
material that transmits from the
visible through the long wave
infrared region
(multispectral ZnS is used)
15

Diamond Could be an Excellent Long Wave Infared Window
(But Not a Midwave Window) if it Were Affordable and
Could be Made in Desired Sizes and Shapes
Transmittance
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Theoretical reflection limit
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Wavelength (μm)
Chemical vapor
deposited diamond
1.74 mm thick
Midwave Long wave
16

•
•
Windows emit radiation at the wavelengths they absorb
Emission from the Window Creates Noise at a Sensor
17

•
•
Most Infrared Transmitting Materials are Highly
Reflective at Radio Frequencies
Dome thickness should be multiple of λ/2 to minimize reflection
Hemispheric geometry is the only practical one for IR/RF dome
so that angle of incidence is always the same
Radome thickness is optimized
to minimize reflection at one
angle of incidence
Hemispheric dome minimizes
reflection of all rays that pass
through the center of the dome
Penalty is severe drag
18

Shielding Effectiveness (dB)
RF Shielding by Square Gold Grid on Sapphire
Observed
Predicted
Frequency (GHz)
Grid spacing is much less than wavelength in this example
If wavelength approaches grid spacing, more leakage occurs
K. T. Jacoby, M. W. Pieratt, J. I. Halman, and K. A. Ramsey, Proc. SPIE 2009, 7302, 73020X
Theory for transmission: S.-W. Lee, G. Zarillo, and C.-L. Law IEEE Transactions Antennas &
Propagation 1982, AP-30, 904
5 µm wide lines
50 µm center to
center

There is a Strong Need for Infrared-Transparent
Electrically Conductive Coatings for
Electromagnetic Shielding
h
P o
P
Conductive coating
Sheet resistance = R s
For example, indium tin oxide has visible transparency and electrical conductivity
There is no known material with adequate infrared transparency and adequate
electrical conductivity
d
Infrared window
Dielectric constant = ε
20

DARPA/ONR Nano-Composite Optical Ceramics Program
100
90
80
70
60
50
40
30
20
10
0
2µm
Raytheon Y 2 O 3 -MgO composite
Transmittance (%)
0 2 4 6 8 10
Wavelength (µm)
Objectives (2007-2011)
•
•
•
2 Compositions
50:50 YM
70:30 MY
of Y2O3-MgO 2 mm thick
Midwave infrared (3-5 μm) transmission
> spinel
Thermal shock resistance > sapphire
Fabricate windows and domes
Raytheon
Nanocerox
CeraNova
University of California,
Davis
Rutgers University
University of Connecticut
21

Raytheon Nanograin Yttria-Magnesia Composite
Provides Mechanical Properties Superior to
Those of Either End Member
Photographed
with visible light
Photographed
with infrared light
22

Aerodynamic Domes and Conformal Windows
Navy SBIR Program (Small Business Innovation Research)
Toroidal glass window made at Penn State
University with OptiPro UltraForm Finishing –
2009
ALON ogive dome made at OptiPro – 2009
23

Example of conformal window: spinel toroid made at Penn State
University with OptiPro UltraForm Finishing – Jan 2010
24

Alumina Dome blank
CeraNova
Final finishing
QED
Aerodynamic Dome Program Elements
Grinding and polishing:
OptiPro, Optimax, CeraNova, Penn State Univ, Univ. Rochester
Metrology
OptiPro
ASE Optics
Breault
Appl. Science Innov.
Applied Science Innovations
OptiPro & ASE Optics
Breault
25

Aerodynamic Dome Program Elements (continued)
Corrective optics
OptiPro (fabrication)
ASE Optics (metrology)
Coating deep concave surfaces
Precision Photonics
26

Transmittance (%)
100
80
60
40
20
0
Transparent Polycrystalline Alumina Could Replace
Sapphire in Some Infrared-Only Applications
• Krell et al, Fraunhofer Institute,
reported infrared transparent Al2 with 0.5 μm grain size in 2003
• Properties similar to sapphire
• Can be made into shapes ―
impractical for sapphire
Sapphire 2.6 mm thick
O 3
Alumina
1.02 mm thick
5.00 mm thick
CeraNova
0.0 0.5 1.0 1.5 2.0 2.5
Wavelength (μm)
(1 mm thick)
Alumina
CeraNova [M. V. Parish & M. R. Pascucci, Proc. SPIE 2009, 7302, 730205]
Polished Hemisphere
(2 mm thick)
Unfinished Dome
27

“Coarse” Metrology with OptiPro UltraSurf Instrument
can Measure a Workpiece During Grinding and
Polishing Before Interferometry Applies
Light Pen:
•
•
Commercial pen from
STIL
Quad Probe from ASE
Optics SBIR contract
28

OptiPro 2009
UltraSurf Measurement of ALON Ogive Dome
with ASE Quad Probe
29

“Fine” Metrology of Free-Form Optics by Interferometry
Applied Science Innovations
• Modular attachment to
commercial interferometer
• Wavefront and surface metrology
• Multiple double-pass transmittedwavefront
maps cover entire
surface
• Solve system of equations to
produce maps of both surfaces
• Reference spherical mirror
• Resolution better than 100 nm
• Sample size limited by size of
spherical mirror only
• Patent 7,545,511 - 2009
Resolved fringes
Unresolved
fringes
Map of broken
wine glass
As reference mirror
is moved, fringes are
produced by limited
regions. Hundreds
of images stitched
together produce
map of both surfaces
and transmitted
wavefront
30

QED Technologies
Rochester NY
Magnetorheological Fluid Jet (MR Jet) Prototype
Jet with
magnet off
Jet with
magnet on
Spindle
Work piece
Nozzle
Fluid collection
Polycrystalline Alumina Dome Concave Surface
Initial figure 1.74 μm P-V Final figure 0.3 μm P-V 31

Airplanes and Ships could use Sensor Windows
Much Larger than Anything Available Today
Sensor windows
Reconnaissance pod
32

Two Approaches to Large Sensor Windows:
1. Scale up size of monolithic window
2. Edge bond windows to make larger windows
TA&T 11 x 18”
spinel
window Surmet
19 x 25” ALON window
33

Adhesive-Free Bonding of Sapphire or Laser Crystals
at Onyx Optics
Bond
line
Fracture
line
H.-C. Lee, H. E. Meissner, X. Mu, C. Liu, and W. Qiu, Proc. SPIE 2009, 7302, 73020A
Polish surfaces to be contacted
to near-atomic flatness
When surfaces are brought into
contact, they stick together
Heat to drive out adsorbed molecules
and increase strength of bond
Sapphire flexure bars joined at the center do
not fracture on the bond line -- indicating that
bond is stronger than sapphire
Disadvantage is difficulty of preparing
optically flat mating surfaces
34

Resonant Cavity Approach to Tri-Mode Seeker Dome
Performance objectives:
• Transmit midwave infrared
• Transmit near-infrared laser
• Transmit millimeter wavelength λ o
• Reject out-of-band radio frequencies
• Durable to survive rain and sand erosion
Dielectric 1
Dielectric 2
Conductive
grid
Gridded, bonded
ALON dome
from Surmet
37

Summary
Generic window problems
• Transparency over all desired wavelengths
• Optical emission
• Rain and sand erosion
• Thermal shock
Infrared materials problems
• Few materials are used: ZnS, Ge, sapphire, MgF2, Si, spinel, ALON
• No long wave infrared material is sufficiently durable
• No multispectral (visible to long wave) material is sufficiently durable
• Good infrared transmitting materials are highly reflective at radio
frequencies
Some Current Technology Development
• Nanocomposite materials with new combinations of properties
• Aerodynamic infrared dome
• Conformal sensor window
• Large area window
• Monolithic
• Edge bonded
Daniel.Harris@navy.mil
38

Multi-Spectral Transparent Materials Technologies
Daniel C. Harris
Naval Air Systems Command, China Lake, California
Ceramic windows and domes protect delicate sensors from harsh environments
while transmitting electromagnetic radiation in one or more spectral
regions. Window material deficiencies that have existed for half a century
include window durability, thermal shock resistance, and optical emission.
There are no very durable materials that transmit both midwave
55 minutes
(3-5 micron)
and long wave (8-12 micron) infrared radiation. Some current thrusts in
window research and development include the fabrication of nanocomposites
with properties not attained by monolithic materials, making conformal
shapes that extend the state of the art in machining and metrology, and
scaling up transparent ceramics to make meter-class windows.
Biographical information: Dan Harris is a Senior Scientist and Esteemed
Fellow at the Naval Air Systems Command in China Lake, California, where he
manages research and development programs in infrared window materials. He
is the author of the monograph "Materials for Infrared Windows and Domes"
and holds degrees in chemistry from MIT and Caltech.

Program Components: Small Business Contracts
N02-155: Nano-Grain Infrared Window Materials
Phase II CeraNova (completed 2006)
N03-009: Nanopowders for IR Window Materials
Phase II MetaMateria (completed 2006)
N04-172: Aerodynamic dome finishing
Phase II + enhancement + Ph II.5 OptiPro
Phase II Creare (completed 2008)
N04-234: Aerodynamic dome blank fabrication
Phase II + enhancement + Ph II.5 CeraNova
Phase II QED (completed Dec 08)
– continues as subcontractor
N06-069: Metrology for Ogive Infrared Dome
Phase II OptiPro + Ph II.5 OptiPro 2010
Phase II Breault
Phase II MetroLaser (completed May 09)
N07-181: Conformal Sensor Window
Phase II OptiPro
Phase II Third Wave Systems
Phase II Applied Science Innovations
+ enhancement 2009
N07-182: Aerodynamic Infrared Dome
Phase II Optimax
Phase II CeraNova
N08-029: Corrective Optics for Conformal
Windows and Domes
Phase II OptiPro
Phase II ASE Optics – Working with OptiPro
metrology
N03-082: Tactical Reconnaissance Window
(Rob Borland technical monitor)
Phase II + enhancement TA&T(completed
Phase II QED (completed 2008)
N08-134: Edge-Bonded Infrared Windows
Phase II Onyx Optics
Phase II MER/Onyx Optics
N04-T009: Nanocomposite optical materials
Phase II Synkera with Raytheon/DARPA
on
2009)
N08-T003: Low-Expansion, Thermal-Shock-Resistant
Dome Material
Phase II Materials and Systems Research
N09-028: Optical Coatings for Deep Concave Surfaces
(Mark Moran technical monitor)
Phase II Precision Photonics
N10-163 High-Strength, Optical Quality Spinel
N10-164 Large-Area, Monolithic Infrared Sensor Window
N10-165 Optically Precise Conformal Sensor Window
40

Planned DDG-1000 Zumwalt-Class Destroyer
Large sensor windows on deckhouse
Wikimedia commons graphic
41