Page 32 - Handbook of Lasers

3+
(LiYF )
Ce
4
2
+
(SrF )
Sm
2
Ti 3+ (Al O )
2
3
3+
Cr (BeAl O , LiSrAlF )
2 6
2 +
V (MgF )
2
4 +
Cr (Mg SiO )
2
4
2
+
(MgF , MgO)
Ni
2
2
+
(MgF )
Co
2
2.5
0.5 2.0
1.0 1.5
Wavelength ( mm)
Figure 1.1.11 Reported wavelength ranges of representative tunable crystalline lasers operating
at room temperature (from the Handbook of Laser Wavelengths, CRC Press, Boca Raton, FL,
1998).
Upconversion processes make possible many additional lasing transitions and excitation
schemes. Upconversion excitation techniques include multi-step absorption, ion-ion energy
transfer, excited state absorption, and photon avalanche processes. Lasers based on
upconversion schemes are noted in the mode column of the laser tables. Transitions
involved in upconversion processes are given in Table 1.1.3 and can be identified by
reference to the relevant energy level diagrams for the ions in Figures 1.1.4–1.1.8. The
success of many of the schemes depends upon the degree of resonance of energy transfer
transitions and the rate of nonradiative transitions by multiphonon emission and thus varies
with the host crystal.
Cascade and cross-cascade lasing schemes have also been employed; transitions involved
in cascade and cross-cascade lasing schemes are summarized in Tables 1.1.4 and 1.1.5. For
examples of avalanche-pumped upconversion lasers, see References 18 and 1037.

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