Excited-state absorption in the pump region of alexandrite

Excited-state absorption in alexandrite has been measured from 420 to 680 nm by using pulsed flash lamp pumping and a dye laser probe. The excited-state absorption cross section is generally of the same order of magnitude as the ground-state absorption cross section (10−19 cm2) and therefore may represent a large loss of energy from the pump source in a laser system. The results were confirmed at two wavelengths with a cw experiment in which 568- or 590-nm radiation was used for pumping and probing.