Data are presented comparing the modal characteristics of short Fabry-
Perot lasers having either AlAs/GaAs or higher contrast ZnSe/CaF2 mirr
ors. The far field radiation patterns, thresholds, and spectral charac
teristics of the lasing modes are studied with a variation of the tran
sverse dimension of the active region. The loss of the lasing mode is
studied in each cavity by comparing lasing threshold and transverse di
mension of the mode for a range of pump diameters