Enhanced 532 nm laser damage threshold and optical performance of KDP crystals by Zn2+ doping

Potassium dihydrogen phosphate (KDP) single crystals doped with a series of trace Zn2+ were prepared by "point seed " technique. The content of Zn of KDP crystal was detected using inductively coupled plasma-optical emission spectrometer (ICP-OES). Small differences were found in Zn content of pyramidal and prismatic samples. The ultraviolet-visible (UV-vis) spectra show that the transmitting percentage of doped KDP crystals in-creases with trace Zn2+ while the transmittance of crystal samples with excessive Zn2+ reduces in UV region. The structural analysis has been performed using infrared spectroscopy (IR). The results illustrate that the crystal network becomes compact after heat treatment or with low concentration doping. The photoluminescence (PL) spectra analysis indicates that the concentration of micro defects of all doped pyramidal samples is lower than that of un-doped samples as well as doped prismatic samples. After thermal annealing, the intensity of PL spectrum of doped sample decreases not obvious compared to un-doped samples. The laser-induced damage threshold (LIDT) results show that the un-doped prismatic sample has relative the lowest LIDT of 3.59 J/cm(2) under the condition of 1-on-1. The LIDT of prismatic sample doped with 1000 ppm Zn2+ reaches 13.88 J/cm2 in the test mode of R-on-1 after heat treatment, which mainly is attributed to the relatively low concentration of micro defects.