ZBLAN glasses

Extensive research including the study of radiative and non-radiative properties of rare-earth ions has been carried out. Especially, the Judd-Ofelt theory has been applied to most rare-earth — fluoride-glass combinations. Typical Judd-Ofelt parameters are reported in Table 3 for ZBLAN glass [31-34], An exhaustive list of such parameters for glasses and crystals can be found in Ref. [35]. 

One of the main spectroscopic properties that differentiate fluoride glasses from silica-based glasses is the low multiphonon emission rate. These non-radiative relaxations that may strongly compete with radiative processes in rare-earth ions are nearly three orders of magnitude lower in ZBLAN glass than in silicate, as shown in Fig. 2. This property is directly related to the fundamental vibration modes of the host and, therefore, varies basically in the same manner as the infrared absorption edge. 

Figure 3 Optical transmission spectra of silica and nonoxide glasses. ZBLAN glass composition is given in Figure 12...

ZBLA glass 2155 Ba35La0Al4 ZBLAN glass 2155 Ba gLagA Na y... 

Fig. 10.6. The einis.sion specirum of Er -dopecl ZBLAN glass in the visible spectral region under infrared excitation. Reproduced with permission from Ref. [6]... 

Fig. 4. DSC scan of ZBLAN glass (10 K/min) showing the graphic procedure for determining 7, 7 ...

Fig. 7. DSC scans for powdered and bulk ZBLAN glasses at 10 K/min scanning rate.

Fig. 9. (a) Nucleation rates for ZBLAN glass NRL (0) and Drehman (1987) data (O (b) crystal growth rate for ZBLAN glass (Hart et at 1988). 

Fig. 20. (a) Far-FTIR specular reflectivity of (1) ZBLA and (2) ZBLAN glasses (b) polarized (HH) components of the Raman spectra of (1) ZBLA and (2) ZBLALiP glasses. 

Fig. 12. (a) Normal fluorescence obtained on a small bulk sample of Er + ZBLAN glass (b) spectrum obtained on the same glass drawn into a 3 m long flber. 

Section 3.1 considered multiphonon relaxation in which the accepting vibrations were modes of the host material itself. As illustrated in Fig. 13, however, multiphonon relaxation can also be introduced by impurities that are present in the material. One possibility is multiphonon relaxation caused by molecular species that are incorporated inadvertently in the host material. Depending on the preparation conditions, hydroxyl (OH ), ammonium (NH4+), sulfate (S04 ), phosphate (P04 ), and carbon dioxide (CO2) species can be present as impurities. Such molecular species are more easily incorporated into the three-dimensional amorphous network of glasses than into crystals. For example, CO2, CO, and O2 gases can dissolve into or react with ZBLAN glass melts (Parker, 1989). Molecular species usually have vibrational modes with much higher energies than the optical phonon modes of the host material. They therefore become likely acceptor modes in multiphonon relaxation and reduce the quantum efficiency ... 

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