Fs-Laser structuring of ridge waveguides

D. Wortmann, J. Gottmann
Appl. Phys. A Vol. 92, No. 1, pp. 197-201

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Thin films made by PLD from Er:ZBLAN and Nd:Gd3Ga5O12, are micromachined to form optical wave guiding structures using Ti:Sapphire and Yb:glass fiber radiation. For the manufacturing of the ridge waveguides grooves are structured by ablation using femtosecond laser radiation. The fluence, the scanning velocity, the repetition rate and the orientation of the polarization in respect to the scanning direction are varied. The resulting structures are characterized using optical microscopy and scanning electron microscopy. Damping and absorption coefficients of the waveguides are determined by observing the light scattered from the waveguides due to droplets in the thin films and the surface roughness of the structured edges. To discriminate between damping due to droplets and the structured edges, damping measurements in the non-structured films and the structured waveguides are performed. Ridge waveguides with non-resonant damping losses of less than 3 dB/cm are achieved. Due to the high repetition rate of the Yb:glass fiber laser, the manufacturing time for one waveguide has been decreased by a factor of more than 100 compared to earlier results provided with the Ti:Sapphire laser. Provided with resonator mirrors and pumped using diode laser radiation the polished waveguides are feasible for integrated waveguide lasers.

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