Up-Conversion in a KGW Crystal by Residual Erbium Ions

We have studied the effect of up-conversion by residual erbium ions, observed in a KGW crystal in the green and red regions of the spectrum upon excitation by the radiation output from diode lasers with wavelengths 808 nm and 970 nm. We demonstrate the existence of different up-conversion regimes under conditions where there is a residual erbium ion concentration. The experimental data indicate up-conversion processes for excitation by laser radiation with wavelength 970 nm with n > 2, where n is a parameter characterizing the dependence of the luminescence intensity on pump power.