On the other hand, high-phonon energy compounds ensure thermal stability and
mechanical rigidity of glass. Moreover, the combination of different glass-forming
elements drives to greater separation of RE ions and enables an effective broadening
of the spontaneous emission spectrum [14]. These investigations require an
unconventional approach to shaping the glass matrix with the complex phonon
distribution, in such a way that the radiation emission can be achieved as a result of
optical transitions within the energy structure of lanthanides. It is a new approach at
the construction of glass in a confrontation with the generally accepted classification
of the glassy matrix in regard to the maximum of phonon energy.
Among oxide glasses, the antimony-based matrices have been widely investigated due to their combination of chemical durability, low-phonon energies
(*600 cm
−1 ) and high transparency in a wide range [15–20]. However, the low
field strength (0.73) of Sb
3+ makes it a poor glass former; hence, it does not exist in
bulk monolithic form which is very much essential for practical applications. The
main advantage of antimony glasses is the ability to create a wide glassy area with
glass-forming components (Ge
4+ , Si
4+ , P
5+ , B
3+ ) which in consequence increase
their thermal stability, needed for fiber production. The phenomenon of antimony
matrix relays on the fact that despite the significant concentration of other
glass-forming components (creating high phonon network), they conserve strong
luminescence form RE elements. On the other hand, peculiar choice in modified
components (Ga
3+ , Te
4+ , Bi
3+ , Ba
2+ , W
6+ ) allows to form antimony glass compositions with no tendency to crystallization and adjust optical parameters like
transmission and refractive index. Another important fact is that Sb 2 O 3 is a mild
reducing agent of noble metal ions. This mild reduction property enables in situ
reduction of Ag
+ to Ag
0 in a one-step during the melting process, thereby providing
a simple, low-cost method for the preparation of bulk photonic materials [21, 22].
Germanate glasses represent a group of the glassy matrix which is characterized
by favorable physicochemical and optical properties as: reduced phonon energy
compared with silica glass, transmission from the visible (Vis) to mid-infrared
(mid-IR) approx. 5.5 µm and possibility of incorporation relatively high concentration of rare-earth ions without the crystallization or phase separation effect (up to
2 mol%). Regarding optical fiber technology, the high thermal stability is a key
parameter and allows its use in active optical fibers and planar waveguides structures thus makes them the object of scientific interest in the leading research centers
[23–27]. Another important aspect is the selection of a modifier and its optimal
concentration. Introduction to the glassy matrix various modifiers (oxide and/or
fluoride) leads to partial depolymerization of the structure of glasses resulting in a
positive or negative impact on their optical and thermal properties. For this reason,
there are many studies on the optimal choice of modifier and its concentration while
maintaining the high thermal stability of the glass.
This chapter contains the results of studies on shaping the luminescence properties of antimony-germanate and germanate glasses with regard to their structural
features. Research on the developed matrices was planned in order to achieve the
following functional properties:
14 The Luminescent Properties of Photonic Glasses …
429
mechanical rigidity of glass. Moreover, the combination of different glass-forming
elements drives to greater separation of RE ions and enables an effective broadening
of the spontaneous emission spectrum [14]. These investigations require an
unconventional approach to shaping the glass matrix with the complex phonon
distribution, in such a way that the radiation emission can be achieved as a result of
optical transitions within the energy structure of lanthanides. It is a new approach at
the construction of glass in a confrontation with the generally accepted classification
of the glassy matrix in regard to the maximum of phonon energy.
Among oxide glasses, the antimony-based matrices have been widely investigated due to their combination of chemical durability, low-phonon energies
(*600 cm
−1 ) and high transparency in a wide range [15–20]. However, the low
field strength (0.73) of Sb
3+ makes it a poor glass former; hence, it does not exist in
bulk monolithic form which is very much essential for practical applications. The
main advantage of antimony glasses is the ability to create a wide glassy area with
glass-forming components (Ge
4+ , Si
4+ , P
5+ , B
3+ ) which in consequence increase
their thermal stability, needed for fiber production. The phenomenon of antimony
matrix relays on the fact that despite the significant concentration of other
glass-forming components (creating high phonon network), they conserve strong
luminescence form RE elements. On the other hand, peculiar choice in modified
components (Ga
3+ , Te
4+ , Bi
3+ , Ba
2+ , W
6+ ) allows to form antimony glass compositions with no tendency to crystallization and adjust optical parameters like
transmission and refractive index. Another important fact is that Sb 2 O 3 is a mild
reducing agent of noble metal ions. This mild reduction property enables in situ
reduction of Ag
+ to Ag
0 in a one-step during the melting process, thereby providing
a simple, low-cost method for the preparation of bulk photonic materials [21, 22].
Germanate glasses represent a group of the glassy matrix which is characterized
by favorable physicochemical and optical properties as: reduced phonon energy
compared with silica glass, transmission from the visible (Vis) to mid-infrared
(mid-IR) approx. 5.5 µm and possibility of incorporation relatively high concentration of rare-earth ions without the crystallization or phase separation effect (up to
2 mol%). Regarding optical fiber technology, the high thermal stability is a key
parameter and allows its use in active optical fibers and planar waveguides structures thus makes them the object of scientific interest in the leading research centers
[23–27]. Another important aspect is the selection of a modifier and its optimal
concentration. Introduction to the glassy matrix various modifiers (oxide and/or
fluoride) leads to partial depolymerization of the structure of glasses resulting in a
positive or negative impact on their optical and thermal properties. For this reason,
there are many studies on the optimal choice of modifier and its concentration while
maintaining the high thermal stability of the glass.
This chapter contains the results of studies on shaping the luminescence properties of antimony-germanate and germanate glasses with regard to their structural
features. Research on the developed matrices was planned in order to achieve the
following functional properties:
14 The Luminescent Properties of Photonic Glasses …
429