Influence of vapor transport equilibration on Raman spectra of Er:LiNbO3 crystals

SEM characterization of micron-sized ErNbO4 precipitates induced in heavily-doped Er:LiNbO3 crystal by vapor transport equilibration

“…These plates were VTEtreated at different VTE conditions. To further confirm the experimental phenomenon that VTE treatment induces the formation of the ErNbO 4 precipitates in a highly Er-doped LiNbO 3 , the VTE conditions in the present work were different from those in our earlier work [2]. The footnotes in Table 1 specify the VTE conditions employed in this work.…”

“…The vapor transport equilibration (VTE) technique has been proved to be a simple and practical method of controlling the Li/Nb ratio in LiNbO 3 crystals. Recently, this technique has been applied to bulk Er-doped LiNbO 3 [1,2]. Preliminary studies have shown that VTE-treated Er:LiNbO 3 crystal reveals a number of interesting spectral characteristics in comparison with the as-grown material [1][2][3][4].…”

“…Our studies have shown that as the doping level of erbium is high enough, e.g., 2.0 mol%, the VTE treatment induces formation of precipitates both in X-cut and Z-cut crystals. The formation of the precipitates inside the crystal results in interesting phonon vibration, absorption and emission features, including remarkable Raman intensity changes of individual phonons [2], significant absorption features in the 1450-1650 nm near-IR range, opacity in the visible range, near transparency at around 1.53 mm [3], substantial weakening of visible emission arising from the scattering effect of the precipitates [4], etc. In addition, the VTE-treated crystal, whether with or without the precipitates, also reveals other absorption and emission features such as a slight shift of peak or band position, slight relative intensity change, the appearance of some additional peaks or bands and the considerable blue shift (about 10 nm) of its optical absorption edge.…”

X-ray diffraction study on formation of ErNbO4 powder

“…(2) A site-selective spectroscopy study has indicated that increasing the Li/Nb ratio with this post-growth material processing effectively reduces the cluster site concentration [22]. From the application perspective, it is interesting because this reduction in the cluster population can reduce the upconversion effect, which is undesirable for applications in Er-based lasing or optical amplification at 1.53 m. (3) A narrowing in line width is observed in Raman scattering [23], visible and infrared absorption and emission measurements [24,25] as a result of the VTE treatment which has brought the crystals closer to the stoichiometric composition, resulting in a reduction of the inhomogeneous broadening. (4) When the doping level of erbium is high enough, 2.0 mol% for example, the VTE treatment will induce the formation of a precipitate, whether the crystal is X-cut or Z-cut [26].…”

“…(4) When the doping level of erbium is high enough, 2.0 mol% for example, the VTE treatment will induce the formation of a precipitate, whether the crystal is X-cut or Z-cut [26]. The formation of the precipitate inside the crystal results in abnormal phonon vibration and absorption features [23,24], including remarkable Raman intensity changes of individual phonons, substantial and interesting absorption features in the 1450-1650 nm region, low clarity in the visible region and near transparency in the 1.5 m region. (5) When the doping level is relatively lower, the crystal not only does not precipitate, but also becomes more transparent (i.e.…”