mid-infrared, enabling construction both laser and broadband emission sources for
the application in integrated systems, precise sensors and medicine. Glasses, in
contrary to crystalline and polymer materials, play an important role here, as they
offer features that are important from the photonic applications point of view. The
most important glass feature is its transparency with a diverse spectral range, as well
as amorphousness, which makes it possible to present a variety of compositions
with properties different from crystals. Although structural amorphousness usually
has a negative effect on optical properties of glass, it makes the technology of
fabricating glass much easier and cheaper, which implies greater functionality. It is
worth to note that the ease of the glass composition modification allows for the
introduction of higher concentrations of active elements (lanthanides) even several
at the same time, thus enabling the manipulation of its luminescent properties and
developing new functional photonics materials.
The operation of the mentioned above systems occurs through the interaction of
optical radiation with lanthanide ions, as a result of excitation and emission in a
strictly defined spectral range, which is dependent on the quantum transitions
within the energy structure of an active element. In practice, we have encountered
several major limitations related to obtaining efficient emissions, i.e.,
• narrow range of spectral transmission of glass;
• high value of phonon energy, which reduces the probability of radial transitions;
and
• low thermal stability of glass, which makes it difficult to use in fiber optic
technology.
A good example is silica glass used in telecommunications (e.g., Erbium Doped
Fiber Amplifier) as well as sources of laser radiation in the range of 1–2 µm
realized by fiber optics doped with Yb
3+ , Nd
3+ , Tm
3+ ions [1–4]. Despite silica
unquestionable advantages, it has limitations related to the absorption edge located
in the infrared range at a wavelength of 2 µm and high-phonon energy of
1100 cm
−1 , which prevents lanthanide emission transitions in the visible range
using a donor-acceptor energy transfer. Therefore, new functional glasses are being
sought that enable efficient emission in the infrared (above 2 µm) and visible range.
The most promising optical glasses which could serve as an alternative in the ranges
mentioned are multi-component systems based on oxides, fluorides and chalcogenides [1, 5–8]. Non-oxide glasses, in particular, have been viewed as a good
solution for many years because of their wide transmission window (up to 20 µm)
and one of the lowest phonon energies (350–500 cm
−1 ). However, the expense of
the fabrication technology, the high toxicity of compounds used, its low mechanical
strength and low thermal stability, strongly limit the practical use of these glasses as
optical fibers [8, 9]. As a result, many research groups around the world have been
focusing their research on oxide and oxide-fluoride glass [10–13].
Special attention has been paid to the issues of fabrication the glassy matrices with
different phonon energy of glass-forming elements. From the one side, low-phonon
energies of glass-forming elements indicate higher efficiency of quantum transitions.
428
J. Zmojda et al.
the application in integrated systems, precise sensors and medicine. Glasses, in
contrary to crystalline and polymer materials, play an important role here, as they
offer features that are important from the photonic applications point of view. The
most important glass feature is its transparency with a diverse spectral range, as well
as amorphousness, which makes it possible to present a variety of compositions
with properties different from crystals. Although structural amorphousness usually
has a negative effect on optical properties of glass, it makes the technology of
fabricating glass much easier and cheaper, which implies greater functionality. It is
worth to note that the ease of the glass composition modification allows for the
introduction of higher concentrations of active elements (lanthanides) even several
at the same time, thus enabling the manipulation of its luminescent properties and
developing new functional photonics materials.
The operation of the mentioned above systems occurs through the interaction of
optical radiation with lanthanide ions, as a result of excitation and emission in a
strictly defined spectral range, which is dependent on the quantum transitions
within the energy structure of an active element. In practice, we have encountered
several major limitations related to obtaining efficient emissions, i.e.,
• narrow range of spectral transmission of glass;
• high value of phonon energy, which reduces the probability of radial transitions;
and
• low thermal stability of glass, which makes it difficult to use in fiber optic
technology.
A good example is silica glass used in telecommunications (e.g., Erbium Doped
Fiber Amplifier) as well as sources of laser radiation in the range of 1–2 µm
realized by fiber optics doped with Yb
3+ , Nd
3+ , Tm
3+ ions [1–4]. Despite silica
unquestionable advantages, it has limitations related to the absorption edge located
in the infrared range at a wavelength of 2 µm and high-phonon energy of
1100 cm
−1 , which prevents lanthanide emission transitions in the visible range
using a donor-acceptor energy transfer. Therefore, new functional glasses are being
sought that enable efficient emission in the infrared (above 2 µm) and visible range.
The most promising optical glasses which could serve as an alternative in the ranges
mentioned are multi-component systems based on oxides, fluorides and chalcogenides [1, 5–8]. Non-oxide glasses, in particular, have been viewed as a good
solution for many years because of their wide transmission window (up to 20 µm)
and one of the lowest phonon energies (350–500 cm
−1 ). However, the expense of
the fabrication technology, the high toxicity of compounds used, its low mechanical
strength and low thermal stability, strongly limit the practical use of these glasses as
optical fibers [8, 9]. As a result, many research groups around the world have been
focusing their research on oxide and oxide-fluoride glass [10–13].
Special attention has been paid to the issues of fabrication the glassy matrices with
different phonon energy of glass-forming elements. From the one side, low-phonon
energies of glass-forming elements indicate higher efficiency of quantum transitions.
428
J. Zmojda et al.