Characterization of channel waveguides in Pr:YLiF4 crystals fabricated by direct femtosecond laser writing

D. Beckmann, D. Esser, J. Gottmann
Appl. Phys. B Vol. 104, No. 3, pp. 619-624

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Single tracks and pairs of tracks are written in the volume of Pr-doped LiYF4-crystals using tightly focused femtosecond laser radiation (λ = 1045 nm, τp = 400 – 500 fs, f = 0.1 – 1 MHz). Waveguiding between the tracks is demonstrated and optimized by varying the distance between the tracks and the laser writing conditions. The stress-induced guiding mechanism is explained based on TEM, interference microscopy, near-field and far-field measurements. It is shown that the single-crystalline material is getting poly-crystalline under femtosecond laser irradiation. By measuring the lifetime of the 3P13H5 transition and the emission spectrum at excitation with λ = 444 nm, no influence on these properties of the guided light is observed. This possibly enables the realization of a channel waveguide laser in the visible spectral range.

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