Excited state absorption of the self-frequency doubling laser material: Nd:GdCOB

Ground-state (GSA) and excited-state absorption (ESA) spectra of Nd 3+ ions in Ca 4GdO(BO 3) 3 were recorded in the 500–560 nm wavelength domain by using an experimental set-up based on a pump–probe technique. We also performed a Judd–Ofelt analysis to determine some of the spectroscopic parameters and to compare the cross-sections which can be derived from this semi-theoretical analysis with the ones obtained experimentally. We thus show that ESA, whatever its polarization be, is probably too weak (cross-section around 1.5×10 −21 cm 2) to affect significantly the green laser emissions at 530 or 545 nm. Moreover, the measured integrated ESA cross-sections are very close to the Judd–Ofelt calculated ones, which makes us confident in our measurements.