Characterization of Cr3+ centres in LiNbO3 using fluorescence line narrowing
Characterization of Cr3+ centres in LiNbO3 using fluorescence line narrowing
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DOI：
10.1088/0953-8984/7/49/026
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发表时间：
1995-12
期刊：
影响因子：
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通讯作者：
P. Macfarlane;K. Holliday;J. Nicholls;B. Henderson
中科院分区：
文献类型：
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作者：
P. Macfarlane;K. Holliday;J. Nicholls;B. Henderson
利用光学吸收、荧光、荧光谱线窄化（FLN）、选择性激发和辐射寿命测量研究了Cr ~（3+）在LiNbO_3中的光谱性质。目前的结果进行了比较，使用其他技术，包括电子自旋共振（ESR）和电子核双共振（ENDOR）获得的数据，并示出是一致的有五个Cr 3+中心。主要的中心是由于在Li+网站，这提供了弱的晶体场，其中Cr 3+离子发射到一个广泛的4 T2到4A 2带的替代。使用FLN，两个中心经历一个更强的晶体场被证明是由于在这个相同的网站，可能是由Nb 5+反位和Nb 5+空位在下一个最近邻的阳离子壳的位置扰动的替代。此外，Mg 2+离子LiNbO 3似乎不会产生新的Cr 3+复合物：相反，它修改了无序的性质，从而改变了不同中心的相对浓度。在这种程度上，它成为可能，以确定其他两个轻占领的Cr 3+中心取代是在Nb 5+网站。LiNbO 3中总共有5个Cr 3+中心，这对所有可用的光谱证据（包括ESR和ENDOR）给出了一致的解释，同时指出了理论工作的困难，在这些理论工作中，Cr 3+离子的能级差异太小，无法通过可用的模型来区分。
The optical spectroscopic properties of Cr3+ in LiNbO3 have been investigated using optical absorption, fluorescence, fluorescence line narrowing (FLN), selective excitation and radiative lifetime measurements. The present results are compared with data obtained using other techniques including electron spin resonance (ESR) and electron nuclear double resonance (ENDOR), and shown to be consistent with there being five Cr3+ centres. The predominant centre is due to substitution at the Li+ site, which provides the weak crystal field in which Cr3+ ions emit into a broad 4T2 to 4A2 band. Using FLN, two centres experiencing a stronger crystal field are shown to be due to substitution at this same site, probably perturbed by the location of Nb5+ antisites and Nb5+ vacancies in the next-nearest-neighbour cation shell. The addition of Mg2+ ions to LiNbO3 appears not to create new Cr3+ complexes: rather it modifies the nature of the disorder, thereby changing the relative concentrations of the different centres. To this extent it becomes possible to identify two other lightly occupied Cr3+ centres where substitution is at the Nb5+ site. This total of five Cr3+ centres in LiNbO3 gives a consistent interpretation of all the available spectroscopic evidence, including ESR and ENDOR, while pointing to the difficulties of theoretical work in sites where the differences in the energy levels of Cr3+ ions are too small to be distinguished by the available models.