Femtosecond laser inscribed waveguides in Nd3+:Y3+:SrF2 crystals

Optical waveguides are fabricated in Nd3+:Y3+:SrF2 crystals by a 1-kHz femtosecond laser using the double-line approach. Waveguides with different separations (10, 15, and 20 \mm m) between two consecutive optical breakdown tracks are produced, and their optical performances are explored by end-fire