LaserDevelopment
Glass at SCHOTT
– December
10, 2007
Laser Glass
at SCHOTT
– 2011
Laser glass development at
SCHOTT
JSH/RDD December 10, 2007 - 1
Laser Glass Development at SCHOTT – 2011
Laser glass production research and
development at SCHOTT
• SCHOTT has produced laser glass in
Pennsylvania since about 1980
• SCHOTT’s Duryea site has complete responsibility for laser glass
research and development, manufacturing, and customer support for
the SCHOTT Group worldwide
• Two developments of critical importance to the glass solid state laser
community:
• Development of platinum particle free melting
• Development of continuous melting of phosphate laser glass
• Recent developments include:
• High repetition-rate laser glass: APG-1/APG-2 (>10 Hz).
• New broad-band phosphate and silicate laser glasses and
higher-power repetition-rated phosphate glasses currently under
development
Laser Glass Development at SCHOTT – 2011
Laser glass historical perspective - keeping pace with the
needs of fusion research
• SCHOTT production
began with silicate
glass for Shiva in
1977
• Production since
1983 has been
dominated glasses
based by on
phosphorous
• The spatial scale of
our products has also
increased over time
Laser Glass Development at SCHOTT – 2011
Development of continuous melting of phosphate laser glass
• The latest generation
of high energy laser
systems for ICF
research (NIF, LMJ)
demanded an
unprecedented volume
of laser glass to be
produced over a limited
manufacturing period
while still meeting
ambitious targets of
internal quality and
overall cost
Artist Rendition of National Ignition Facility (NIF) Laser
Laser Glass Development at SCHOTT – 2011
Traditional laser glass was produced in a two step
process that includes remelting in a platinum crucible
• Starting materials would
react with and alloy the
platinum pot
• However, refractory
materials such as SiO2 are
also dissolved into the
batch, leading to
inhomogeneity in the glass
• Remelting of “cullet” glass
in platinum avoids the
alloying problem and makes
high homogeneity glass
possible
• Remelting cullet glass still
allows the inclusion of Pt
particles
Laser Glass Development at SCHOTT – 2011
Elimination of platinum inclusions increases laser
damage threshold by 10X
• In the absence of Pt
inclusions, the
damage threshold of
laser glass optical
components is now
limited by the quality of
the surface polish
Laser Glass Development at SCHOTT – 2011
Damage grows with successive shots above the
damage threshold
• Redeposited
platinum vapor of
spatial size
>0.3m can
damage on the
next shot
• Below 0.3m,
the heat is
conducted into
the glass
• Laser glass parts
became unusable
after only a few
high power shots
Laser Glass Development at SCHOTT – 2011
The key to solving the Pt particle problem was to
dissolve the particles into the glass structure as ionic
Pt4+
• Platinum particles appear
to be created at the start of
the melt cycle
• Dissolution is limited by
diffusion of platinum away
from the particle surface
• Care must be taken to
avoid the late arrival of Pt
particles into the melt from
condensed vapors
Laser Glass Development at SCHOTT – 2011
To meet schedule and cost targets NIF and LMJ required
both a new glass and a new manufacturing process
• The NIF laser alone required 3000
slabs (150 metric ton) over 3 years
with the following specifications:
• Index uniformity to <±0.000001
• Free of inclusions and bubbles
larger than 100um
• Residual hydroxyl content
<100ppmw
• Platinum particle free
• Free of all detectable striae
• Low 1054nm absorption of
<.19% per cm thickness
Beamlet eighteen liter rare earth
doped phosphate glass amplifier slab
Laser Glass Development at SCHOTT – 2011
Meeting the laser glass requirements in terms of cost,
quality, and rate of delivery for NIF demanded the
development of an advanced manufacturing technology
1. Raw Batching
Material
To Scrubber
Exhaust
5. Homogenizer
Process Control
Lab Samples
Continuous
Monitoring All
Properties
4. Refiner
2. Melter 3.Conditioner
Melt and Form
8. Cut /
Inspect
6. Forming
7. Annealing Lehr
• Continuous melting runs 24 hours a day / 7 days per week
• 100% Inspection, interferometry and laser damage testing
Laser Glass Development at SCHOTT – 2011
SCHOTT conceived, designed, and demonstrated
the full scale continuous production line from 1994 to 1999
• Over 1400 laser slabs were first
produced by the new continuous
melting process in 2001
• All technical specifications and
targets for the NIF were surpassed
• 26% of slabs were essentially
perfect, far exceeding overall
specifications for residual water,
platinum particles and homogeneity
• Laser glass deliveries for the NIF
and LMJ were completed in March
2004
Laser Glass Development at SCHOTT – 2011
Current laser glass research and development at SCHOTT
• Ongoing $2.8M Production contract for discontinuous
melting laser slabs and rods.
• Awarded $2.5M for development of next-generation
silicate and phosphate laser glasses are under
development
Glass Type
Nd:Silicate vs. LG-680
Nd:Phosphate vs. APG-1
Yb:Phosphate vs. Yb:APG-1
Key Progress
FOMTM
Bandwidth
FOMTM
Bandwidth
FOMTM
Bandwidth
Aug., 09
TBD
TBD
TBD
TBD
TBD
TBD
Feb., 10
-2%
+6 nm
-55%
+4 nm
-5%
+5 nm
Sept., 10
+1 / + 164%
+11 / +6 nm
+30%
+7nm
+30%
+12 nm
FOM TM 
K IC k (1  )
E
Laser Glass Development at SCHOTT – 2011
Process Development – Summary
• SCHOTT has been a major supplier of laser glass since 1980
• SCHOTT has also been active in the development of new
manufacturing technology extending the operation range and
lowering the cost of our products
• This activity has created at SCHOTT further understanding on
glass and supported the application of our other products into the
marketplace
• The two most critical developments in the last 20 years have been
the availability of platinum particle free laser glasses and the
continuous melting of phosphate laser glass
• Our efforts in laser glass are industry recognized and promote our
reputation as the lead supplier of optical materials for laser
applications