Effects of energy-transfer up-conversion and excited-state absorption in quasi-three-level Nd: GdVO₄lasers

We investigate in detail the effect of energy-transfer up-conversion (ETU) and excited-state absorption (ESA) in diode-end-pumping quasi-three-level Nd:GdVO₄ lasers. The energy levels of Nd:GdVO₄ crystals and the rate equation involving ETU and ESA effects are presented. The results of simulation show that the ETU effect is important in quasi-three-level lasers and can provide heating approximately two times higher than that induced by the ESA. Moreover, the relationship between the incident pump power and the 912 nm output power was simulated taking into account the ESA; a comparison with experimental data is also presented. As a result, we conclude that the ESA plays an important role in the high-power pumping field; the estimated equivalent cross-section σ_ESA = (1.0 ± 0.5) · 10^-20 cm².