Page 317 - Tunable Lasers Handbook

6 Transition Metal Solid-state hsers 77

TABLE 6 Physical Properties of MgF, -

Parameter Value Units

Lattice constants
a axis 162.3
c axis 305.3
Density 3170
Heat capacit? 989
Thermal conductivity 20.6
Thermal expansion
u axis 13.1
c axis 8.8
Refractive index
a axis 1.3768
c axis 1.3886
Refractive index variation
a axis 1.12
c axis 0.58
Optical transparency 0.12-6.5
Melting point 1163

mance has been achieved so far. One reason for this is excited state absorption
[57]. Excited state absorption might be expected by considering iis similarities
with Cr. In general, excited state absorption occurs in Cr materials as laser oper-
ation shifts toward longer wavelengths. Doubly ionized V is similar to triply ion-
ized Cr and VMgF, operates around 1.12 pm, so excited state absorption is
probable. Excited state absorption would likely occur between the 4T, and the
TI manifolds. Although excited state absorption occurs for Ni:MgF,, - its effects
do not preclude reasonable operation of this material.
Absorption bands in Ni:MgF, are strong enough to allow flashlamp or laser
pumping. Absorption bands for Ni peak in the vicinity of 1.35 and 0.79 pm for
the ?A, to Ti", and the 34 to jT1 manifolds, respectively, as shown in Fig. 27.
Absorption between th,ese manifolds is relatively weak, producing n polarized
absorption coefficients on the order of 100 m-1 for a Ni concentration of 0.01.
Stronger absorption is associated with the TT, manifold in the blue region of the
spectrum. Laser pumping is enabled by utilizing the long-wavelengrh absorption
band around 1.35 pm.
Strong absorption bands in Co:MgF, occur between the TI and ?A, mani-
folds, which peak at about 1.35 pm for both TC and (3 polarizations as shown in
Fig. 28. The spectral bandwidths of both of these features are about 0.26 pm [%I.