Page 235 - Chalcogenide Glasses for Infrared Optics

CHAPTER 9

AMI Infrared

Crystalline

Materials

ven though the company was completely dedicated to infrared
glasses, at both TI and AMI the author was involved in
Eproducing crystalline materials useful in infrared technology.
Expertise at AMI was imported when colleagues from TI joined AMI
and led efforts to produce crystalline materials needed in govern-
ment programs.

9.1 Cadmium Telluride
Cadmium telluride first became known as an infrared optical mate-
rial as one of the hot pressed polycrystalline Kodak Irtran materials.
Kodak developed a group of materials, all made using the same pro-
cess. Fine-grain high-purity powders were placed in a mold, sealed
from the atmosphere, heated to a temperature just below the melting
point, and molded into a disk using very high pressure. The resulting
disk had density very near that of the melt grown material. When
polished, they showed high transmission in the infrared and were
used to form lenses or serve as windows. They were also strong
because of their particulate structure. The designations and materials
used to make them were as follows: Irtran 1, MgF ; Irtran 2, ZnS;
2
Irtran 3, CaF ; Irtran 4, ZnSe; Irtran 5, MgO; and Irtran 6, CdTe.
2
Optical and physical properties of these materials are described in
detail in a Kodak Publication U-72 released in September 1971.
Along about 1970, the U.S. Air Force was funding a great materials
effort to develop a window suitable for use with high-energy lasers to
be mounted in an aircraft. All infrared window materials were being
evaluated for this application. One of the leaders in theoretical studies
1
of infrared optical materials was Marshal Sparks of XONICS. Specific
materials were characterized by Stanley Dickinson in an Air Force
2
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