| This thesis examines some dynamics of nonradiative decay that take place in Nd3+:YLiF4 (Nd:YLF), Nd3+:Y 3Al5O12 (Nd:NAG), and Nd3+:LaF 3 (Nd:LaF3) in their ground state 4f3 and excited state 4f25d configurations. These investigations were carried out using femtosecond laser-based pump-probe techniques.; A pump-probe experiment employing a red (∼780 nm) pump to the 4F5/2 and 2H(2)9/2 manifold of Nd3+, and a blue (∼390 nm) probe to the fluorescing 2F(2)5/2 level (via excited state absorption from the former level), was able to measure the nonradiative decay rate of the 4F 5/2 and 2H(2)9/2 manifold from the rate of exponential decay of 2F(2)5/2 fluorescence as a function of pump-probe delay time. Decay tunes of 230+/-30 ps for Nd:YLF, 18+/-6 ps for Nd:YAG, and 550+/-80 ps for Nd:LaF3 were measured. Each of these measurements is in good agreement with the multiphonon energy gap law, based on other 4f3 nonradiative decay measurements that have been published for these types of doped crystals.; A similar excited state absorption pump-probe experiment was attempted, employing red (∼770 nm) pump and probe beams to measure the 4F 7/2 and 4S3/2 manifold lifetime while monitoring 2P3/2 fluorescence. However, the acquired results do not reflect the anticipated 4F7/2 and 4S 3/2 nonradiative decay lifetimes in Nd:YLF, Nd:YAG, or Nd:LaF3 . The recorded 2P3/2 fluorescence appears to be dominantly produced by an excitation mechanism combining 4F 3/2 upconversion processes and excited state absorption of 4 F3/2 fluorescence.; Some experiments that attempt to measure intra-configuration 4f25d relaxation rates in Nd:YLF are described. The first is a pump-probe absorption experiment which failed to sample transient signal that could be ascribed to 4f25d relaxation dynamics: undoped samples such as amorphous glass, ZnSe, and sapphire were able to produce very similar signals as a function of pump-probe delay time. A more rigorous experiment involving stimulated emission out of the 4f25d configuration into a fluorescing 4f3 level was attempted, but the desired results were too weak to be seen. |
