A technique of direct writing of depressed cladding waveguides by a femtosecond laser beam in doped YAG laser crystals has been developed. A low threshold buried waveguide laser in the YAG:Nd3+ crystal has been demonstrated. Spectroscopic investigation of the crystal modified by a femtosecond laser beam and phase delay measurements of refractive index change in series of YAG crystals lead to conclusion that the refractive index change is due modifications in a defect system of a doped YAG crystal, while crystal lattice persists during this process.

© 2005 Optical Society of America

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