Precision Grating and Optics for Space Research
Precision Grating and Optics for Space Research
Precision Grating and Optics for Space Research
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<strong>Precision</strong> <strong>Grating</strong> <strong>and</strong> <strong>Optics</strong> <strong>for</strong> <strong>Space</strong> <strong>Research</strong><br />
Mark L. Schattenburg<br />
<strong>Space</strong> Nanotechnology Laboratory<br />
Kavli Institute <strong>for</strong> Astrophysics <strong>and</strong> <strong>Space</strong> <strong>Research</strong><br />
Massachusetts Institute of Technology<br />
University of Alabama at Huntsville<br />
Aug. 5, 2005<br />
<strong>Space</strong> Nanotechnology Laboratory<br />
SNL<br />
Massachusetts Institute of Technology
Bizarre-Universe.eps<br />
Supernova Remnant<br />
Huge jets many times longer than our galaxy.<br />
Exhaust from the supermassive black hole.<br />
Supernovae can emit more energy than<br />
the combined output of all the billions of stars in our galaxy.<br />
Supermassive Black Hole<br />
Our Bizarre Universe<br />
The centers of galaxies harbor black holes that can have<br />
more mass than all the stars of our galaxy combined.<br />
Star Being Eaten by Black Hole<br />
Cosmic vacuum cleaner.<br />
Galactic Jet<br />
Huge jets many times longer than our galaxy<br />
are the exhaust from supermassive black holes.
MLS-01-03-14.02<br />
NASA Ch<strong>and</strong>ra Observatory X-ray Telescope<br />
Per<strong>for</strong>ms high-resolution x-ray imaging <strong>and</strong> spectroscopy in the<br />
energy range of 0.1-10 keV (wavelengths from 0.1 to 10 nanometers).<br />
Subrahmanyan<br />
Ch<strong>and</strong>rasekhar<br />
(1910-1995)<br />
Nobel Prize, 1983
cc_GrazingIncidence.ai<br />
θ c<br />
Principles of X-ray <strong>Optics</strong> at Grazing Incidence<br />
Refractive index <strong>for</strong> x-ray radiation:<br />
n(<br />
ω) = 1−<br />
δ ( ω)<br />
+ iβ<br />
( ω)<br />
where δ , β ∼<br />
Critical angle <strong>for</strong> total external reflection of x-rays:<br />
n = 1−<br />
δ + iβ<br />
θ<br />
Critical Ray<br />
Grazing Incidence Radiation <strong>and</strong><br />
Total External Reflection<br />
θ = 2δ<br />
c<br />
Totally<br />
Reflected<br />
Rays<br />
Reflectivity<br />
~10 -2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
C<br />
A<br />
B<br />
D E<br />
0.5 1 1.5 2 2.5 3<br />
θ / θ c<br />
10 -4<br />
A : β / δ = 0<br />
B : β / δ = 10<br />
C : β / δ = 10<br />
D : β / δ = 1<br />
E : β / δ = 3<br />
−2<br />
−1
MLS-2001-05-23.01.eps<br />
X-rays<br />
Ch<strong>and</strong>ra Observatory Grazing Incidence <strong>Optics</strong><br />
(Wolter Type I)<br />
Nested<br />
Hyperboloids<br />
Nested<br />
Paraboloids<br />
1.1 Meter Diameter<br />
Doubly-<br />
Reflected<br />
X-rays<br />
10 Meters<br />
Focal<br />
Plane
Ch<strong>and</strong>ra-Mirror.eps<br />
Ch<strong>and</strong>ra X-ray Telescope Mirror Assembly<br />
Raytheon Optical Systems & Eastman Kodak Corp.
HETGS<br />
NASA Ch<strong>and</strong>ra Observatory X-ray Telescope<br />
High Energy Transmission <strong>Grating</strong> Spectrometer (HETGS)<br />
Aspect Camera<br />
Stray Light Shade<br />
High Resolution<br />
Mirror Assembly<br />
(HRMA)<br />
Sunshade<br />
Door<br />
Thrusters (4)<br />
(105 lb)<br />
Low Gain<br />
Antenna (2)<br />
<strong>Space</strong>craft<br />
Module<br />
Transmission<br />
<strong>Grating</strong>s (2)<br />
Optical<br />
Bench<br />
Ch<strong>and</strong>ra Telescope<br />
X-rays<br />
X-ray<br />
mirrors<br />
P H<br />
<strong>Grating</strong><br />
(in use)<br />
Solar Array (2)<br />
CCD Imaging<br />
Spectrometer<br />
(ACIS)<br />
High Resolution<br />
Camera (HRC)<br />
Integrated Science<br />
Instrument Module<br />
(ISIM)<br />
<strong>Grating</strong><br />
(stowed)<br />
CCD1 CCD2 CCD3 CCD4 CCD5 CCD6<br />
HETGS Instrument<br />
X-ray CCD<br />
Detector array<br />
θ<br />
Zero-order beams<br />
Diffracted beams<br />
Rowl<strong>and</strong> Torus Transmission <strong>Grating</strong> Geometry <strong>and</strong> CCD Readout Array
MLS-2001-05-11.01eps<br />
NASA Ch<strong>and</strong>ra X-ray Observatory<br />
High Energy Transmission <strong>Grating</strong> Spectrometer (HETGS)<br />
HETGS instrument.<br />
1.1 meter<br />
Invar grating frame.<br />
3 cm<br />
Scanning electron micrograph of gold grating.<br />
100 nm<br />
550 nm
E0102-72.eps<br />
Ch<strong>and</strong>ra X-ray Spectrum<br />
Small Magellanic Cloud Supernova Remant E0102-72<br />
Direct X-ray Image (CCD Camera)<br />
longer wavelengths <br />
shorter wavelengths<br />
X-ray Image Dispersed by Transmission <strong>Grating</strong>s<br />
Zero<br />
Order
MLS-1999-05-26.03.eps<br />
Variable<br />
Attenuator<br />
Mirror<br />
Beamsplitter<br />
p = λ<br />
2sinθ<br />
Interference Lithography<br />
Beamsplitter<br />
Spatial Filters<br />
2θ<br />
Pockels Cell<br />
Substrate<br />
Laser Beam<br />
λ = 351.1 nm<br />
Phase Error<br />
Sensor<br />
Mirror
MLS-94-05-13.01<br />
15 nm<br />
Ta 2 O 5<br />
0.5-1.0 µm<br />
ARC<br />
5 nm chromium<br />
20 nm gold<br />
200 nm<br />
resist<br />
0.5-1.0 µm<br />
polyimide µ<br />
d<br />
silicon wafer<br />
silicon<br />
(a) Prepare substrate.<br />
polyimide<br />
Membrane-Supported Transmission <strong>Grating</strong><br />
Fabrication Process - Macro View<br />
(b) Pattern gold grating.<br />
gold<br />
grating<br />
(c) Acid spin-etch wafer<br />
backside.<br />
adhesive<br />
(d) Bond to Invar frame.<br />
(e) Cut away.<br />
silicon<br />
Invar<br />
frame
MLS-94-05-13.02<br />
resist<br />
ARC<br />
polyimide<br />
silicon<br />
ARC<br />
polyimide<br />
silicon<br />
(b) Pattern by IL<br />
<strong>and</strong> develop.<br />
Membrane-Supported Transmission <strong>Grating</strong><br />
Fabrication Process - Micro View<br />
(a) Prepare<br />
substrate.<br />
interlayer<br />
plating<br />
base<br />
ARC<br />
polyimide<br />
silicon<br />
(c) Etch interlayer in<br />
CF 4 RIE plasma.<br />
polyimide<br />
silicon<br />
(d) Etch ARC in O 2<br />
RIE plasma.<br />
plated gold<br />
polyimide<br />
silicon<br />
(e) Gold electroplate.<br />
plated<br />
gold<br />
polyimide<br />
silicon<br />
(f) Strip interlayer<br />
<strong>and</strong> ARC.<br />
polyimide<br />
epoxy<br />
Invar<br />
(g) Acid spin-etch<br />
substrate.<br />
Align <strong>and</strong> bond<br />
to frames.
MLS-2001-05-25.02.eps<br />
Reflectivity from Resist/IL Boundary<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
0<br />
Gold Transmission <strong>Grating</strong> Fabrication Process<br />
Benefit of anti-reflection coating (ARC).<br />
Resist<br />
ARC<br />
Silicon<br />
Ta 2 O 5<br />
200 nm period<br />
λ = 351.1. nm<br />
TE polarization<br />
0 200 400 600 800<br />
ARC Thickness (nm)<br />
<strong>Grating</strong> after oxygen plasma RIE of ARC.<br />
100 nm<br />
600 nm<br />
<strong>Grating</strong> after interference lithography.<br />
100 nm<br />
<strong>Grating</strong> after gold plating <strong>and</strong> resist stripping.<br />
100 nm<br />
resist<br />
ARC<br />
Ta 2 O 5
MIT<br />
SNL<br />
NASA Constellation-X
MIT<br />
SNL<br />
Smooth Ch<strong>and</strong>ra Monolithic <strong>Optics</strong>
MIT X-ray Telescopes Utilizing Thin<br />
Required optic<br />
dimensions:<br />
100mmx140mmx0.4mm<br />
Length / thickness > 200<br />
SNL<br />
<strong>Optics</strong>
MIT<br />
SNL<br />
Grazing Incidence (Wolter I) <strong>and</strong><br />
Reflection <strong>Grating</strong> <strong>Optics</strong>
MLS-2002-08-19.01.eps<br />
100 mm<br />
p max<br />
X-ray Reflection <strong>Grating</strong> Geometry<br />
(Off-Plane Diffraction)<br />
pave
Super-Smooth Blazed Reflection <strong>Grating</strong>s From Miscut Silicon<br />
200 nm Resist<br />
30 nm SiN<br />
1. Coat with bilevel resist <strong>and</strong> pattern gratings.<br />
Silicon<br />
2. Plasma etch ARC <strong>and</strong> nitride.<br />
3. RCA clean.<br />
49 nm ARC<br />
(111) planes<br />
4. Anisotropic KOH etch.<br />
5. Remove nitride with HF.<br />
Resist<br />
Anti-reflection Coating (ARC)<br />
Nitride<br />
(111) planes
200 nm Si Master with 7º Blaze<br />
AFM probe<br />
100<br />
Silicon Master<br />
Scanned profile<br />
Actual profile<br />
• Roughness < 0.2 nm<br />
• Rounding = AFM artifact<br />
• Radius of probe ~ 10 nm<br />
Coated with Cr <strong>and</strong> Au<br />
Atomic Force Micrograph (AFM) Scanning Electron Micrograph (SEM)<br />
SNL MIT
MLS-1997-01-20.08.eps<br />
Resist<br />
Left<br />
Beam<br />
Interference Lithography<br />
2<br />
Substrate<br />
<strong>Grating</strong> Period p=/(2sin)<br />
Right<br />
Beam
MLS-2000-04-03.01.eps<br />
Spherical waves cause<br />
hyperbolic phase.<br />
Hyperbolic Phase<br />
Traditional Interference Lithography<br />
laser<br />
laser<br />
Figure errors & defects<br />
in collimating optics cause noise.<br />
Linear Phase + Noise
MLS-2000-04-04.02.eps<br />
Optical<br />
Bench<br />
Interferometer<br />
Scanning-Beam Interference Lithography<br />
Laser<br />
XY Stage<br />
Air Bearing Granite Block<br />
Substrate<br />
Y Direction<br />
Y Direction<br />
X Direction<br />
Parallel Scanning<br />
X Direction<br />
Doppler Scanning<br />
Scanning<br />
<strong>Grating</strong><br />
Image<br />
Air-Bearing<br />
X-Y Stage<br />
Resist-<br />
Coated<br />
Substrate<br />
Scanning<br />
<strong>Grating</strong><br />
Image
PTK-99-01-09-1<br />
Y Direction<br />
X Direction<br />
(a) Scanning Scheme<br />
Intensity<br />
Scan<br />
1<br />
<strong>Grating</strong> Scanning Method<br />
<strong>Grating</strong><br />
Image<br />
Air-Bearing<br />
Stage<br />
Substrate<br />
Summed Intensity<br />
of Scans 1-6<br />
Scan<br />
2 Scan<br />
3<br />
Scan<br />
4<br />
Scan<br />
5<br />
Intensity<br />
Scan<br />
6<br />
(b) Image Intensity Profile<br />
(c) Overlapping Scans<br />
Closely Approximate<br />
a Uni<strong>for</strong>m Intensity<br />
Distribution<br />
X<br />
<strong>Grating</strong><br />
Period<br />
p=λ/(2sinθ)<br />
X
sbil-readwrite.eps<br />
DSP/<br />
Phase Meters<br />
Stage Error<br />
Frequency<br />
Synthesizer<br />
AOM-2<br />
AOM-3<br />
f 2 =f 1 +f lock<br />
PM-2 PM-1<br />
Substrate<br />
X-Y Stage<br />
SBIL Reading <strong>and</strong> Writing Modes<br />
UV Laser<br />
f 3 =120 MHz<br />
AOM-1<br />
f 1 =100 MHz<br />
DSP/<br />
Phase Meters<br />
Stage Error<br />
Frequency<br />
Synthesizer<br />
PM-4<br />
AOM-2<br />
f 2 =90 MHz<br />
PM-3<br />
X-Y Stage<br />
Writing Mode Reading Mode<br />
UV Laser<br />
AOM-1<br />
f 1 =110 MHz<br />
Revised 3/21/05 MLS
Planned_system.eps<br />
D/A PMC<br />
A/D PMC<br />
IXC6 Master/<br />
DSP/Power PC<br />
SBIL System Opto-Electronic Architecture<br />
host<br />
processor<br />
ZMI 2002<br />
VME Bus<br />
ZMI 2002<br />
ZMI 2002<br />
UV (=351 nm) Signal<br />
From Interference<br />
Lithography Reading <strong>and</strong><br />
Writing Interferometers<br />
Digital Change<br />
of State Board<br />
TTL Digital<br />
Output<br />
ZMI 2002<br />
VME Rack<br />
Power<br />
Supply<br />
Fiber Reference<br />
Signal<br />
Fiber Optic<br />
Interferometers<br />
Limits<br />
Motor<br />
Current<br />
Comm<strong>and</strong>s<br />
Laser<br />
Head<br />
5U Motor<br />
Driver/Amplifier<br />
Limit<br />
X Motor<br />
Motor<br />
Power<br />
Supply<br />
Limit<br />
Y1 Motor<br />
Motor<br />
Stage<br />
Mirror<br />
Y2 Motor<br />
Motor<br />
To Digital<br />
Frequency<br />
Synthesizer
MLS-2004-11-29.03.eps<br />
MIT Nanoruler with 300-mm Silicon Wafer
ptk-enclosure-032903.eps<br />
Nanoruler Environmental Enclosure<br />
Temperature Control ±0.005 C<br />
Humidity Control ±1% RH
• Gravity sag<br />
Foil Optic De<strong>for</strong>mation<br />
• Thermal expansion<br />
mismatch between foil<br />
<strong>and</strong> constraint device<br />
• Friction from physical<br />
manipulation (i.e.,<br />
assembly)<br />
SNL MIT
Double-sided<br />
flexures (3)<br />
Silicon wafer<br />
Horizontal<br />
tilt stage<br />
Thin Optic Metrology Truss<br />
SNL MIT<br />
x<br />
z<br />
y<br />
Vertical tilt stage<br />
Reference block<br />
Antenna<br />
flexures (4)
Monolithic Flexures<br />
Double-sided flexures Antenna flexures<br />
SNL MIT
Double-Sided Flexure Design<br />
Opposing<br />
arms<br />
Vertical<br />
arm<br />
Point of<br />
actuation<br />
Vertical arm<br />
• Allow <strong>for</strong> optic insertion/removal<br />
Optic insertion/removal<br />
Thin optic<br />
Point of<br />
actuation<br />
• Provide preload<br />
SNL MIT
Double-Sided Flexure Design<br />
Thermal expansion compensation<br />
Thin optic<br />
Opposing<br />
arms<br />
Thermal<br />
load<br />
Opposing arms<br />
Opposing arm<br />
misalignment errors<br />
• Accommodate thermal expansion up to 1°C per measurement<br />
• Manufactured using wire electric-discharge-machining of<br />
SNL stress-relieved aluminum<br />
MIT
Load Carrying Flexure Design<br />
Reduce friction-induced warp<br />
Sapphire tube<br />
to facilitate<br />
optic<br />
placement<br />
Cylindrical<br />
flexure<br />
Carry the load of optics up to 1.6 mm thick<br />
SNL MIT
MIT<br />
SNL<br />
Magneto-Rheological Finishing<br />
QED Technologies<br />
Abrasive Particles<br />
Iron Particles
Wafer B: 4 MRF front side polishes, 1 back side: PV ~ 3 µm 75 nm
MLS-2001-05-28.01.eps<br />
Microstructures <strong>for</strong> High-Resolution X-ray Foil Optic Assembly<br />
500 m<br />
Old Technology New Technology<br />
Stainess-steel wire-EDM combs.<br />
Very low accuracy (> 20 microns).<br />
Poor optic resolution (>1 arcminute telescope).<br />
Silicon micromachined combs.<br />
500 m<br />
500 m<br />
Spring Comb Reference Comb<br />
Very high accuracy (
MLS-2002-03-15.02.eps<br />
Reference Surface<br />
Silicon Microcombs Establish Accurate Metrology Frame<br />
Reference Comb<br />
Spring<br />
Tooth<br />
Foils<br />
Spring Comb<br />
Foil<br />
Reference<br />
Tooth<br />
1 mm 1 mm
MLS-2001-05-28.02.eps<br />
microcombs etched through<br />
entire wafer<br />
100 mm<br />
silicon wafer<br />
Micro-comb Fabrication Process Overview<br />
Silicon Wafer<br />
a) Grow thermal oxide.<br />
b) Photolithography.<br />
c) Reactive ion etch oxide.<br />
d) Attach quartz h<strong>and</strong>le-wafer.<br />
e) Deep reactive ion etch silicon.<br />
f) Extract finished micro-combs.<br />
Silicon Wafer Oxide Resist Quartz
Microcombs<br />
Assembly truss<br />
Modular Assembly<br />
Reference flat<br />
Reflection <strong>Grating</strong>s<br />
Flight module
Comb Alignment-Flexure Bearings<br />
• Simple<br />
• No friction<br />
– Sensitive<br />
– Long life<br />
• Integrated <strong>for</strong>ce<br />
sensor<br />
– Ref. flat contact<br />
– Study comb damage<br />
Flexure Bearings<br />
Microcombs<br />
Micrometers
Graduate Students<br />
Minsueng Ahn (ME)<br />
Mireille Akilian (ME)<br />
Chih-Hao Chang (ME)<br />
Carl Chen (EECS)<br />
Craig Forest (ME)<br />
Chulmin Joo (ME)<br />
Paul Konkola (ME)<br />
Juan Montoya (EECS)<br />
Yanxia Sun (ME)<br />
Yong Zhao (ME)<br />
Acknowledgements<br />
<strong>Research</strong> Staff<br />
Robert C. Fleming, Semiconductor Process Engineer (Lab Manager)<br />
Dr. Ralf K. Heilmann, <strong>Research</strong> Scientist (Lab Assistant Director)<br />
Yeon-Oh Jung, Visiting Engineer<br />
Lab Web Site: http://snl.mit.edu<br />
We are grateful to NASA, DARPA, <strong>and</strong> NSF <strong>for</strong> support of this research.<br />
<strong>Space</strong> Nanotechnology Laboratory<br />
SNL<br />
Massachusetts Institute of Technology
IMAGE.eps<br />
NASA Imager <strong>for</strong> Magnetopause-to-Aurora<br />
Global Exploration Mission (IMAGE)<br />
Medium Energy<br />
Neutral Atom Detector (MENA)
Magnetosphere-2.eps<br />
Earth’s <strong>Space</strong> Environment: The Magnetosphere<br />
<strong>Space</strong> Weather
Charge-Exchange-2<br />
TRAPPED<br />
A magnetically trapped ion captures<br />
an electron from a neutral<br />
hydrogen atom...<br />
Charge Exchange<br />
FREE<br />
...creating an energetic neutral atom<br />
(ENA) that is no longer trapped.
MENA-Concept-2.eps<br />
D 1<br />
START Foil<br />
2.6 nm Carbon<br />
STOP<br />
MENA Neutral Atom Camera<br />
Measurement Concept<br />
Collimator HWHM:<br />
±55º imaging plane<br />
±2º spin plane<br />
UV<br />
Nanofilters<br />
Ionized Atom<br />
X 1<br />
α<br />
Ground<br />
Grid<br />
Primary MENA<br />
Accelerating<br />
Grid<br />
START Electrons<br />
tan(α) = X 2 - X 1<br />
L<br />
tan(δα) = cos(α)<br />
L<br />
X 2<br />
D 2<br />
MCP Stack<br />
Position<br />
Sensive<br />
Anode<br />
START Position (D 1 )<br />
+<br />
STOP Position (D 2 )<br />
Polar<br />
Angle<br />
Time of Flight<br />
+ Species<br />
Pulse Height<br />
Time of Flight<br />
+ Energy<br />
Species
Filter.eps<br />
UV<br />
+<br />
Atoms<br />
Nanofilter<br />
<strong>Grating</strong><br />
Atoms<br />
Detector<br />
Nanofilter UV-Blocking Transmission <strong>Grating</strong>s<br />
Electron micrograph of gold nanofilter.<br />
45 nm<br />
UV Transmission Coefficient<br />
10 -1<br />
10 -3<br />
10 -5<br />
λ=121.6 nm<br />
(Hydrogen Lyman Alpha)<br />
10 -9<br />
10 -7<br />
30 nm gap width<br />
40 nm gap width<br />
50 nm gap width<br />
60 nm gap width<br />
0 100 200 300 400 500 600 700 800<br />
Thickness (nm)<br />
Electron micrograph of lines be<strong>for</strong>e electroplating.<br />
45 nm<br />
Resist<br />
IL<br />
ARC<br />
PB
MLS-98-05-06<br />
(a) Wafer Preparation<br />
resist<br />
ARC<br />
SiN<br />
silicon<br />
plated nickel<br />
gold grating<br />
SiN<br />
silicon<br />
(f) Mounting<br />
plating<br />
base<br />
(Cr/Au)<br />
adhesive<br />
Mesh-Supported <strong>Grating</strong> Fabrication Process<br />
Interlayer<br />
(Ta 2 O 5 )<br />
(c) Pattern Support Grid<br />
metal frame<br />
(d) Wafer Etch<br />
gold <strong>and</strong> nickel gratings<br />
Silicon<br />
(b) <strong>Grating</strong> Patterning<br />
patterned resist<br />
plated gold<br />
ARC<br />
SiN SiN<br />
SiN<br />
silicon<br />
SiN<br />
(g) Backside Etch<br />
silicon<br />
(b1) Pattern resist. (b2) Etch <strong>and</strong> plate. (b3) Strip resist.<br />
(e) Plug Pinholes<br />
resist exposed resist<br />
UV<br />
(e1) Spin resist <strong>and</strong> UV expose.<br />
plated nickel<br />
(e2) Plate nickel <strong>and</strong> strip resist.
MLS-2001-05-25.04.eps<br />
Nanofilter <strong>Grating</strong><br />
(gold)<br />
155 nm line<br />
45 nm space<br />
Support <strong>Grating</strong><br />
(nickel)<br />
UV Nanofilter <strong>Grating</strong> Support Mesh Design<br />
Triangular<br />
Support Mesh<br />
(nickel)<br />
Completed<br />
Flight <strong>Grating</strong><br />
(Stainless Steel Frame)<br />
4.0 µm 346.4 µm 10 mm
MLS-01-03-14.01.eps<br />
Pinhole Plugging Results<br />
200 m<br />
Pinholes Be<strong>for</strong>e Plugging<br />
200 m<br />
4x 4x<br />
Pinholes After Plugging
MLS-2001-05-11-02.eps<br />
IMAGE Medium Energy Neutral Atom Camera (MENA)<br />
Magnetospheric Storm Observations<br />
(August 12, 2000)<br />
Shadow Shadow<br />
Sun Sun<br />
9:30 UT 22:00 UT<br />
Frames from an oxygen atom "movie."<br />
(Elapsed time between frames is 12.5 hours.)
MIT<br />
Flatness vs. Thickness Variation<br />
Double-<br />
Side<br />
Polishing<br />
SNL<br />
a) b) c)<br />
Polishing pads<br />
a) Ideal thin optic<br />
b) Uni<strong>for</strong>m thickness<br />
Non-flat surfaces<br />
c) Flat right surface<br />
Normal Force<br />
Non-flat left surface<br />
Non-uni<strong>for</strong>m thickness<br />
Be<strong>for</strong>e polishing After polishing
MIT<br />
SNL<br />
Shaping Glass<br />
Slumping<br />
Strain temperature: lowest annealing temperature<br />
Softening temperature: temperature at which glass de<strong>for</strong>m under its own weight
MIT<br />
SNL<br />
Slumping onto <strong>Precision</strong> M<strong>and</strong>rels<br />
dust particles<br />
thin substrate epoxy<br />
replicated surface<br />
after separation<br />
flat m<strong>and</strong>rel flat m<strong>and</strong>rel flat m<strong>and</strong>rel<br />
(a) (b) (c)<br />
smooth m<strong>and</strong>rel<br />
thin substrate<br />
(a) (b)
MIT<br />
SNL<br />
Artificial ‘dust’: Pin Chuck<br />
•Microetched fused silica/silicon to get regular pin pattern<br />
•TiO 2 coating to roughen the contact surface<br />
250 µm<br />
dust particle<br />
5-25 µm<br />
thin substrate<br />
flat m<strong>and</strong>rel<br />
25 µm<br />
pin chucks<br />
50nm<br />
25nm<br />
(a) (b)<br />
flat m<strong>and</strong>rel
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