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

Optical waveguides are fabricated in Nd 3+ :Y 3+ :SrF2 crystals by a 1-kHz femtosecond laser using the double-line approach.Waveguides with different separations (10, 15, and 20 µm) between two consecutive optical breakdown tracks are produced, and their optical performances are explored by end-fire coupling to 780-and 532-nm lasers.Propagation loss of the waveguide with 20-µm separation is estimated.The microphotoluminescence and micro-Raman spectra indicate that the original fluorescence and lattice structure of the Nd 3+ :Y 3+ :SrF2 crystals are well preserved in the waveguide.Therefore, the obtained waveguide structures are promising candidate for application in integrated waveguide lasers.