Page 234 - Chalcogenide Glasses for Infrared Optics

210 Cha pte r Ei g h t

bundle to serve as a container protecting the fragile fibers from
breakage. Cladding of the fibers with glass was not used in order to
speed up the drawing process, to increase the active area of the bundle
to over 70 percent, and to provide flexibility. Crosstalk at the bundle
ends did not occur because epoxy used to fuse the ribbons served as
cladding. Unclad fibers transmitted almost as well as clad fibers
because of the high refractive index (2.4) of As S glass. Both ends of
2 3
the bundle were antireflection—coated to increase transmission in
the 3- to 5-µm camera wavelength band. Purification methods used
in preparation of the arsenic trisulfide glass have enabled absorption
levels at 2.44 µm of 0.1 to 0.2 dB/m to be met, at 2.92 µm (H O) below
2
1 dB/m has been achieved, and < 5 dB/m at 4 µm due to H S have
2
been met. However, unexpected broadening of the absorption by the
impurity bands for a 10-m optical path led to a decrease in internal
transmission in the 3- to 5-µm band to 37 percent. When multiplied
by the 70 percent active area, total transmission drops to 26 percent,
or one-half of the program goal of 50 percent. Sufficient energy exists,
nonetheless, for producing useful images when used with a very
good sensitive camera and suitable optics.

References
1. A. R. Hilton, Sr., “As-Se-Te Based Glass Fibers,” SPIE 1228, 76 (1990).
2. A. R. Hilton, Sr., A. R. Hilton, Jr., J. McCord, and T. J. Loretz, “Preparation of
Coherent IR Chalcogenide Glass Fiber Bundles,” SPIE 2131, 192 (1994).
3. A. R. Hilton, Sr., A. R. Hilton, Jr., and T. J. Loretz, “A Progress Report, Fabrication
of IR Coherent IR Glass Fiber Bundles,” SPIE 2677, 15 (1996).
4. A. Ray Hilton, Sr., “Infrared Imaging Bundle Development at Amorphous
Materials,” SPIE 3849, 61 (1999).
5. A. R. Hilton, Sr., A. R. Hilton, Jr., J. McCord, W. S. Thompson, and R. A. LeBlanc,
“Infrared Imaging with Fiber Optic Bundles,” SPIE 5074, 849 (2003).
6. A. R. Hilton, Sr., “Final Scientific and Technical Report, Fiber Optic Coupled
IRFPA,” Contract NOO-97-10421-97-C-1046, 1999; and Ray Hilton, Sr., et al.,
“Fabrication of a 10 Meter Length IR Imaging Bundle From Arsenic Trisulfide
Glass Fibers,” SPIE 3596, 64 (1999).
7. A. R. Hilton, Sr., A. R. Hilton, Jr., James McCord, and Glen Whaley, SPIE 3060,
325 (1997).
8. A. R. Hilton, Sr., Method for Constructing a Coherent imaging Bundle. U.S.
Patent 5,938,812, August 1999.