Biomedical Engineering Reference
In-Depth Information
glasses as well as some unique characteristics that can lead to novel
developments in photonics. Avnir et al.
7,8
demonstrated for the first time
that organic molecules can be added to a sol-gel matrix and thin films. Since
then, many groups around the world have introduced organic materials into
a variety of inorganic matrices via the sol-gel process. Sol-gel processed
materials have been used in the areas of solid-state lasers and in platforms
for chemical and biosensors.
9,10
The sol-gel technique has also been used to
fabricate non-linear optically active composites for applications in optical
telecommunications.
11
Organically modified and sol-gel processed materials
were shown to exhibit excellent non-linear optical
(3)
properties.
The sol-gel method also provides a more convenient route to prepare
luminescent glass optical fibers doped with rare earth (RE)
(2)
and
χ
χ
ions,
12,13
waveguides
14,15
and lasers.
16
To date, there are only a few sol-gel derived materials that meet the
materials quality required for fabricating devices. One of the major
problems has been to produce useful bulk materials with controlled doping
(organic and inorganic) at the nanoscale. Another problem has been the
fabrication of a low-loss optical fiber with active species incorporated within
it. Sol-gel approaches show promising results in producing useful materials
for photonics. They include: (i) RE-doped glasses; (ii) multiphasic
nanostructured composites, which combine the merits of inorganic glass
and an organic polymer; and (iii) optical fibers with active molecules
incorporated within the fiber matrix and dispersed homogeneously for
sensing or lasing applications.
3.2
Optical properties of ceramic nanocomposites
Many of the interesting optical properties of ceramic nanocomposites,
including absorption, fluorescence, luminescence and non-linearity, may be
studied by incorporating semiconductor nanoparticles into polymer, glass or
ceramic matrix materials. Nanocomposite structures have been used to
create optically functional materials, and in all these systems, very small
particle sizes (see Fig. 3.2) enhance the optical properties while the matrix
materials act to stabilize the particle size and growth. Laser-active
composites can be made by incorporating ceramic nanoparticles of solid-
state laser materials into polymer matrix materials. This structure allows the
formation of solid-state laser amplifying films, which would traditionally be
very difficult to make. Nanocomposite structures provide a new method to
improve the processability and stability of materials with interesting optical
properties. The applications of such composites are extremely broad,
ranging from solid-state amplifier films to transparent magnets.
1
In nanocomposites, light scattering is remarkably reduced compared to
composites with larger particles. This renders nanocomposite materials
