High-Nonlinearity in Glass Fibers and Cross-Phase Modulation - Optical Signal Processing by Silicon Photonics - page 62

There is another possibility that if we consider that the interaction of the two
spectral components which are mostly dominant of Single-Phase Modulation and
the spectrum of single pulse are broadened. Two side-bands appearing in the pulse
spectrum at the same time are showing that a connection is presented in this analy-
sis. It is observed from these experiments that the normal dispersion regime side-
bands can be interpreted as XPM-induced modulation instability [ 13 , 14 ].

5.6 High-Nonlinearity Glasses

Optical glasses with fast response time and high third-order nonlinearities are very
promising materials for ultrafast nonlinear fiber devices [ 15 , 16 ]. The third-order
optical nonlinearity is the most important property for realization of ultrafast all-
optical switching. This section addresses the general properties of HNL Glasses of
Lead-Oxide (PbO, Litharge), Bismuth-Oxide (Bi 2 O 3 , Bismite), Tellurium-Oxide
(TeO 2 ,Tellurite), and Chalcogenide glasses with a focus on their nonlinear prop-
erties such as the third-order susceptibility and nonlinear-index coefficient. The
characteristics of the conventional and microstructure fibers made of those HNL
glasses are also discussed.

5.6.1 Bismite (Bi 2 O 3 ) Glasses

Bismite is derived from the ignition of bismuth nitrate which in turn is obtained
from the heavy metal bismuth. The latter is very similar to lead; however, there is
no evidence of toxicity and it has been used in low-temperature frits, as a flux in
conductive glazes and in metal enamels. Bismite has been used instead of litharge
in amounts up to 50 % in optical glasses to improve durability and to increase the
specific gravity and the refractive index. Arsenic is often used with it to prevent a
tendency toward grey coloration. Bismite is a very effective substitute for litharge,
providing the same high gloss, flow, bubble clearance characteristics, high refrac-
tive index, surface tension, viscosity, and resistance to aggressive dish washer
detergents. Bismite melts at a lower temperature than litharge and thus glazes can
be even more fluid. The properties of Bi 2 O 3 -based glasses are summarized below:
(a) High linear refractive index (1.87 ~ 2.6)
(b) High nonlinear-index coefficient (32 ~ 1,810 × 10 − 20[m 2 /W])
(c) Very wide transmission range (0.45 ~ 5 μ m)
(d) Transition temperature (~500 °C) and melting temperature (~900 °C)
(e) Fusion-spliceable to SiO 2 -based glasses
(f) Easy integration to silica-based systems
(g) High mechanical, chemical, and thermal durability
(h) Simple and easy fabrication process
(i)

No toxicity.