Page 185 - Handbook of Lasers

Unlike crystals, which have a unique composition and structure, many glasses may be
formed in broad compositional ranges with varying parentages of glass network formers
(e.g., silicate, phosphate, borate) and network modifiers (e.g., alkali ions, alkaline earths
ions). Compositional changes affect the stimulated emission cross sections, rates of radiative
and nonradiative transitions, crystalline field splittings, and inhomogeneous broadening.
Although trivially small compositional changes might technically constitute a new host
material, the lasers listed in the tables in Section 1.2.2 are generally characterized by either
significantly different host glass compositions or different operating properties, thus the
tables are representative rather than exhaustive with respect to all glass lasers reported.

Because of site-to-site variations in the local fields in glass, there is a distribution of
energy levels and transition frequencies that appear as inhomogeneous broadening and
provide a small degree of tunability. Examples of reported tuning ranges of lanthanide-ion
glass lasers are shown in Figure 1.2.3.

Upconversion excitation techniques involving multi-step absorption, energy transfer,
excited state absorption, and photon avalanche have also been exploited for glass lasers.
Examples of upconversion pumping schemes that have been used for fluorozirconate fiber
lasers are given in Table 1.2.2.

In addition to glass laser operation involving a single transition, several cascade lasing
schemes have been demonstrated, although not as many as for crystalline lasers (see Table
1.1.1). These schemes for glass lasers are summarized in Table 1.2.3. In all cases the lasers
have utilized fluorozirconate fibers and have operated at room temperature.

0.5 1.0 1.5 2.0 2.5 3.0

Pr 3+ : fluorozirconate:

Nd 3+ :silica:

Ho 3+ : fluorozirconate:

Er 3+ : fluorozirconate:

Tm 3+ : fluorozirconate:

Yb 3+ :silica:

0.5 1.0 1.5 2.0 2.5 3.0
Wavelength ( mm)
Figure 1.2.3 Reported tuning ranges of lanthanide-ion glass lasers (see Tables for specific
wavelengths and host glasses).

©2001 CRC Press LLC