Ridge waveguides have been fabricated in Nd:YAG single crystal by using femtosecond laser micromachining in an oxygen ion irradiated planar waveguide. The microphotoluminescence features have been found well preserved in the waveguide structures. Continuous wave lasers have been realized at 1.06 µm at room temperature in the ridge waveguide system with a lasing threshold of ~39 mW and a slope efficiency of 35%, which show superior performance to the planar waveguide. "Ultraviolet nanosecond laser-assisted micro-modifications in lithium niobate monitored by Nd 3+ luminescence," Appl. Phys., A Mater. Sci. Process. 87(1), 87-90 (2007). 26. R. Ramponi, R. Osellame, and M. Marangoni, "Two straightforward methods for the measurement of optical losses in planar waveguides," Rev.
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