Luminescence spectra and kinetics of congruent LiNbO$_3$ : Er crystals in temperature range 80 – 420 K

The photoluminescence (PL) spectra and kinetics of congruent LiNbO$_3$ : Er crystals under laser excitation at $\lambda$ = 405 nm have been investigated in the $T$ = 80 – 420K range. The PL spectrum of LiNbO$_3$ : Er crystal in the visible wavelength range consists of four multiplets whose maxima are located at $\lambda$ = 413, 526, 551, and 660 nm. It is found that at $T$ = 300K PL decay-time ($\tau_{\mathrm{PL}}$) at $\lambda$ = 526 and 551 nm is $\tau_{\mathrm{PL}}$ $\sim$ 27 $\mu$s, and the PL band with a maximum at 413 nm decays faster than 1 $\mu$s, which correlates with numerous literature data. At the same time it is found that at $\lambda$ = 660 nm $\tau_{\mathrm{PL}}$ = 33 $\mu$s, which is almost 30 times larger than previously published values. Possible reasons for the observed difference are discussed.