Picosecond kinetic confirmation of overlapping Ca cluster and MNa absorption bands in UV grade CaF_2

摘要

The ArF laser induced absorption feature between 450 and 700 nm observed in the bulk of mono crystalline calcium fluoride (CaF_2) upon prolonged 193 nm irradiation is shown to have two origins: The first band at 530 nm is revealed by a transient femtosecond (fs) laser transparency spectrum and attributed to Ca clusters (colloid). The second band at 600 nm originates from MNa centers as identified by their laser induced fluorescence excitation spectrum, emission wavelength, and fluorescence lifetime. The analysis of the absorption feature by fs pump-probe techniques benefits from the different lifetimes of the transient transparency (excited states of the Ca clusters) and the fluorescing Mna centers of about 5 ps and 22 ns, respectively.