Page 40 - Chalcogenide Glasses for Infrared Optics

Chalcogenide Glasses 19

establishing a similar glass production facility. Funding for this pur-
pose by the Air Force covered the years 1967 through 1974.
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Also in 1967, a Materials Advisory Panel was formed headed by
Norbert Kreidl, a noted glass scientist and former director of research
at Bausch and Lomb. The author was a member of the panel. One of
the recommendations of the panel was that a program be funded to
develop zinc selenide as an infrared optical material. The Air Force
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decided to fund a Raytheon program headed by Jim Pappis. The
development at Raytheon of the chemical vapor deposition method
to produce plates of small-grain zinc selenide and zinc sulfide has
been a very important advancement in the production of infrared
optical elements.
In 1967, the Air Force Production Development Program at TI
was transferred to the Semiconductor Production Division under the
direction of Charlie Jones, a colleague of the author from the Central
Research Laboratory. Joining the effort was Harold Hafner who had
just joined TI. His background was in glass science as he had served
as deputy research director at Bausch and Lomb under Norbert
Kreidl. Hafner made many important contributions including a glass
casting process and a glass tempering process. The program concen-
trated the efforts on a glass from the germanium-arsenic-selenium
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system. TI results agreed with the conclusions of the Russian, U.K.,
and Servo efforts that the germanium-arsenic-selenium system pro-
duced the best glasses for infrared system applications. Don Weirauch
at TI conducted a crystallization study on the germanium-arsenic-
selenium family of glasses and identified a composition in which
crystallites would not form. The composition was fully characterized
and produced at Texas Instruments as TI 20 glass. No patent could be
granted for the glass since the glass system was reported in several
places in the literature. One of the accomplishments of the program
was to increase the rupture modulus of TI 20 from 3000 to 6000 psi by
tempering. In 1972, a window of TI 20 glass was cast 12 in × 24 in × 0.5 in,
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polished flat and parallel and antireflection-coated. The window
was installed in a U.S. Navy F4 in front of its FLIR system. The plane
on returning to Florida flew into a hailstorm, which shattered the
window and damaged the FLIR. Thus started the rain erosion testing
of infrared optical materials at the facility at Wright-Patterson Air
Force Base.
Attempts were made at TI to develop a business selling infrared
glass outside the company. Brochures and advertising were employed.
Little in sales resulted. The program had reached a production stage
and was moved to the Electro-Optics Division, the user division. Pro-
duction of TI 20 was stopped as well as sales of chalcogenide glasses
outside the company.
In 1972–1973, TI had to produce the glass in quantity and quality
for the Navy P3 system. Their yields were so low that glass blanks
began to cost more than the system. In 1974, the author left TI Central