ABSTRACT
Nd3+-doped fluorozirconate-based glasses which contain hexagonal BaCl2 nanocrystals are analyzed for their photoluminescence and multiphonon relaxation (MPR) properties. The MPR rates of various Nd3+ levels are obtained from time-resolved spectroscopy using selective laser pulse excitation. The nonradiative decay rates are estimated from the difference between measured and calculated radiative decay rates as well as from the analysis of luminescence rise times. The MPR rates display an exponential dependence on the energy gap. Temperature-dependent studies of the decay indicate that phonons of the BaCl2 nanocrystals are involved in the MPR processes leading to extremely low MPR rates which are orders of magnitude lower than in conventional oxide and halide glasses. Photoluminescence emissions,which are usually quenched by MPR, and enhanced radiative quantum efficiencies are found.
ABSTRACT
We have investigated the nonlinear refractive index of ex-vivo pig cornea by a combined approach using the standard z-scan technique on extracted corneas or corneal slices, as well as studying the deviations caused by self-focusing during femtosecond laser processing of the pig eyes. The experiments yield consistently an upper limit of 1.2 MW for the critical power of self-focusing in porcine cornea, and a value of 2 x 10(-19) m(2)/W for its nonlinear refractive index. We also demonstrate that due to this nonlinear refraction the cutting depth of typical fs-laser surgery processing in cornea may depend considerably, albeit in a well controllable way, on the laser parameters.
