Page 253 - Chalcogenide Glasses for Infrared Optics

228 Cha pte r Ni ne

1.0

Bulk absorption coefficient (cm –1 ) 0.01
0.1

0.001
4 µm 5 µm 6 µm 7 µm
2500 2000 1500 1200
–1
Wave number (cm )
FIGURE 9.12 Infrared absorption coeffi cient for AMI vacuum fl oat zoned
silicon as a function of wavelength.

laser emitting at 2.94 µm. No measurable absorption for the 12-cm
crystal was observed. No damage resulted from the intense radiation
2
estimated to be 4 MW/cm after 10 min of irradiation. Results show
high-purity single-crystal silicon was suitable for use with high-
intensity NIR lasers pulsed or CW.

9.6 Single-Crystal Silicon Fibers
There was great interest in developing flexible infrared fibers to be
used with these high-intensity lasers. Silica fibers were extremely
low in absorption in the visible region, but because of water absorp-
tion cut off before 2 µm. Attention shifted to fluoride glasses with
some success. Polycrystalline materials were extruded but suf-
fered from light scatter and breakage at grain boundaries when bent.