Spectroscopic study of trivalent neodymium ions in potassium yttrium fluoride crystals

KYF{dollar}sb4{dollar} is a new kind of fluoride laser crystal. Nd{dollar}sp{lcub}3+{rcub}{dollar} ions in KYF{dollar}sb4{dollar} crystals have a short lasing wavelength (1040nm), which may be interesting for some special applications. The luminescence lifetime of Nd{dollar}sp{lcub}3+{rcub}{dollar} ions in KYF{dollar}sb4{dollar} is longer than that of Nd{dollar}sp{lcub}3+{rcub}{dollar} in many other laser materials, which make Nd{dollar}sp{lcub}3+{rcub}{dollar} doped KYF{dollar}sb4{dollar} crystal a good potential material for Q-switched laser operation.; In this research work we conducted spectroscopic measurements on three Nd{dollar}sp{lcub}3+{rcub}{dollar} doped KYF{dollar}sb4{dollar} crystals with different concentrations of Nd{dollar}sp{lcub}3+{rcub}{dollar} ions (2%, 3%, and 4%). We performed a detailed study of the absorption spectra, continuous luminescence spectra, excitation spectra and dynamic decay spectra; especially the emission behavior and lifetime behavior at different temperatures in the range 20K to 300K.; In this study we found that the Nd{dollar}sp{lcub}3+{rcub}{dollar} ions in KYF{dollar}sb4{dollar} have an anomalous strong dependence of lifetime and emission intensity on temperature in the range below 100K, which we call as abnormal spectral behavior. Based on the special crystal structure of KYF{dollar}sb4,{dollar} we proposed an explanation for this abnormal behavior by using an energy transfer model. Nd{dollar}sp{lcub}3+{rcub}{dollar} ions in KYF{dollar}sb4{dollar} may occupy six different sites, which may be classified into two main sites with significant different environments. Energy transfer is found to take place between the Nd{dollar}sp{lcub}3+{rcub}{dollar} ions at these different sites.; We carried out a detailed calculation of the radiative transition properties of Nd{dollar}sp{lcub}3+{rcub}{dollar} ions in KYF{dollar}sb4{dollar} crystal by using the Judd-Ofelt theory. From these calculations learned that the radiative transition rate of Nd{dollar}sp{lcub}3+{rcub}{dollar} ions in KYF{dollar}sb4{dollar} is smaller than that in many other Nd{dollar}sp{lcub}3+{rcub}{dollar} laser material, and correspondingly the radiative lifetime is longer. The spontaneous emission cross section for the laser transition is smaller in KYF{dollar}sb4.{dollar} A detailed comparison of the radiative properties of the KYF{dollar}sb4{dollar} crystal with those of other laser Nd{dollar}sp{lcub}3+{rcub}{dollar} crystals and laser glasses is presented.