Page 266 - Chalcogenide Glasses for Infrared Optics

AMI Infrar ed Crystalline Materials 241

The improvement appears to be related to their relative hardness.
John Hall of the U.S. Army Night Vision Laboratory at Ft. Belvoir
became a driving force for the use of GaAs in place of germanium in
the infrared systems in the Army tanks. He organized a meeting to
consider nongermanium optical materials for 8- to 12-µm FLIR pro-
duction. Of particular importance were the optical requirements for
the Horizontal Integration GEN II FLIR program scheduled to supply
thousands of M1-Abrams, M8-AGS, and M2 Bradley tanks with sec-
ond-generation FLIRs. The meeting was held at Ft. Belvoir in May
1994. Attendees included TI (GaAs), Eagle Picher (Ge), Morton Inter-
national (ZnSe-ZnS), Exotic Materials (Ge), and AMI (GaAs).
Presentations were made describing materials produced and
advances made recently. The reader has already learned what AMI
25
presented. The TI presentation by Paul Klocek was very extensive,
demonstrating the amount of effort expended and progress made
over the last several years. TI enthusiasm for the change to GaAs
seemed lacking. The situation in optical Ge and Si production by
Dennis Thomas of Eagle Picher was positive. The Morton presenta-
tion by Dennis McAllister for ZnSe and ZnS production covered
all the widely used CVD materials. Design and fabrication were dis-
cussed. Hall talked about new designs using GaAs including some he
had already made and tested. His conclusion was that GaAs will
prove to be very useful for Army FLIR applications and can dramati-
cally improve the ability of the HTI Gen II FLIR to meet range and
bore sight performance in high-temperature environments by reducing
the total amount of Ge used. John Hall’s words were correct, but
resistance at high levels of decision authority led to continued use of
Ge optics in all HTI Gen II FLIR systems. 26
Hall was successful in codeveloping with personnel from Hughes
El Segundo an HTI-compatible, GaAs-based imager which is still
used by the Night Vision Lab for special testing. Hall eventually left
the Night Vision Lab and joined the private sector. He continues to
find applications for GaAs optics in the new dual-band “Gen III” sensor
systems. Hall has already delivered prototype systems to the Night
Vision Lab that have been used for very successful demonstrations
and data collection since 2006. 27
Meanwhile, AMI found great interest on the part of designers
and system engineers at Lockheed Martin in Orlando to use GaAs
in their upgrade of the TADS PNVS helicopter system. Working
with senior optical designer Al Lyon and optics production man-
ager Bob Icovazzi of LMCO, AMI began supplying small amounts
of GaAs for prototype designs using the AMI units. Finally, in late
1994, AMI on a best-efforts basis agreed to attempt to grow a single-
crystal plate in which the flat faces would have the desired crystal-
line orientation, <100>, as determined by a seed placed in the melt.
The purpose was to produce an outside surface less susceptible to
rain impact damage. Obviously, use of the horizontal Bridgman was