We present some strong evidence against the assignment of an ytterbium-related oxygen deficiency center (ODC) near in Yb-doped aluminosilicate glass in the Letter by Yoo et al. [Opt. Lett. 32, 1626 (2007)] . The strong absorption band is actually a charge-transfer band corresponding to the transfer of an electron from nearby oxygen ligands to the ytterbium ion and not related to ODCs.
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