Er,Yb:YAl3(BO3)4 crystalline layers grown by liquid-phase epitaxy

In this paper, Er,Yb:YAl₃(BO₃)₄ layers were tested as passive optical waveguides. Using a microscope objective with a numerical aperture of 0.4, the beam of a Ti: sapphire laser at 900 nm was focused onto the incoupling end-face of the waveguide. The outcoupled light was collected with another microscope objective and imaged onto the chip of a CCD camera. As expected for a 50 mum thick film, several waveguide modes were observed. The propagation losses were measured, which is based on the determination of the longitudinal distribution of fluorescence light along the waveguiding direction, obtained at different excitation wavelengths. The excitation wavelength was tuned from 900 to 1000 nm and the resulting fluorescence intensity at 1.5 mum was detected using a Ge photodiode. The parasitic propagation losses were measured to be approximately 2 dB/cm in the 50 mum-thick Er,Yb:YAl₃(BO₃)₄ waveguide.