Spectral hole burning in thulium-doped glass ceramics

We have used spectral hole burning to measure the homogeneous linewidth of the H-3(6)(1)-F-3(3)(1) transition of Tm3+ ions doped into oxyfluoride glass ceramics consisting of nanocrystals of LaF3 in an aluminosilicate glass matrix. From the magnitude of the hole width in the nanocrystals and its dependence on temperature, we propose that excitation of tunneling modes in the adjacent glassy phase as well as of confined mechanical modes in the nanocrystals is responsible for the broadening. (C) 2001 Optical Society of America.