Fluoride glasses: ZBLAN

Tick et al. (1995) modified this system by adding Znp2 and YF and doping solely with the rare-earth ion Pr (Table 4-12) at the low level of 0.1 mol%. The luminescent quantum efficiency of Pr emission at the 1300 nm telecommunication band was measured at 7%, an improvement over similar Pr emission from the well-known fluoride glass, ZBLAN , measured at 4%. These glass-ceramics... 

Day and France found that the addition of lead fluoride to ZBLAN fibers caused, however, a marked increase of the Rayleigh coefficient (A = 1.12 dB km-1 nm4) [20], [21], Very likely, this is due to an increase of the concentration of submicron crystallites related to the lower stability of ZBLAN-Pb glass, as compared to pure ZBLAN. 

Typical of sodium-containing glasses such as ZBLAN or BIG-Na, another way to increase the refractive index is to substitute Li+ for Na+ ions, despite the lower polarizability of lithium ions because of their small size. Actually, Li+ ions are so small that they induce a local collapse of the glassy network resulting in an increase of the densification and of the refractive index [10,24,25]. This property is utilized for the elaboration of fluoride glass planar waveguides by ionic exchange, as described in Sec. 5.3. 

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]. 

Judd-Ofelt parameters Q, (r = 2, 4, 6) of rare-earth ions in ZBLAN fluoride glasses... 

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. 

Lasing has been demonstrated at 1.06 /tm in Nd3+-doped ZBLAN and BIG fluoride glass rods pumped by an alexandrite laser and xenon flashlamps, respectively [71,72], Fig. 6 shows the 1.06 //m laser output energy out of Nd3+-doped and Cr3+ Nd3+-codoped fluoroindate glass rods of 40 mm length. In presence of Cr3+ ions, which are efficient absorbers of excitation light from flashlamps,... 

Characteristics of rare-earth-doped ZBLAN fluoride glass fiber lasers, (i) incident, (1) launched, and (a) absorbed pump powers, (uc) up-conversion pumping... 

Characteristics of fluoride glass optical amplifiers. All fibers are ZBLAN-based glass except when otherwise indicated. (LD) laser diode ( ) gain obtained with two amplification units. 

Fig. 3. Composite loss spectra for some common IR fibre optics ZBLAN fluoride glass SC sapphire, chalcogenide glass, PC AgBrCl, and hollow glass waveguide plot reproduced from Harrington, 2010.

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