Multi-scan femtosecond laser waveguide inscription in z-cut Lithium Niobate

We describe the femtosecond inscription of waveguides in z-cut lithium niobate using the multi-scan technique. The form of modified regions and their relationship with writing pulse energy and scan speed is examined. An insertion loss of 3.5 dB at 1550 nm was measured for an 18 mm long waveguide coupled to single-mode fibers.