Time-resolved photoluminescence spectroscopy of Nb4+ and O− polarons in LiNbO3 single crystals


Time-resolved photoluminescence spectroscopy of Nb4+ and O− polarons in LiNbO3 single crystals

Kämpfe, T.; Haußmann, A.; Eng, L. M.; Reichenbach, P.; Thiessen, A.; Woike, T.; Steudtner, R.

Abstract

We probe here the optical relaxation properties of Mg-doped wide-band-gap LiNbO3 single crystals with both a high spectral and temporal resolution at cryogenic temperatures. Surprisingly, we observe the photoluminescence to decay in a two-step process: a fast relaxation and a slower one centered around an energy Emax=2.62±0.05 eV. Both decays fit well to the stretched-exponential behavior. Moreover, we are able to associate these energies to the recombination of light-induced Nb4+ and O− small polarons. Also, we checked the stability of our findings by using LiNbO3 single crystals that show on-purpose modified radiative recombination processes, i.e., with a Mg doping both above and below the optical damage resistance threshold, as well as with different poling histories of inverted domains.

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