Praseodymium ion doped K⁺ -Na⁺ thermal ion-exchangeable waveguide-adaptive aluminum germanate glasses

Intense multi-peak red fluorescence and effective near-infrared (NIR) ultra-broadband emission have been observed in Pr³ doped ion-exchangeable aluminum germanate (NMAG) glasses. The maximum emission cross section for ³P₀ → ³F₂ red emission is up to 100.58 × 10^-21 cm², and the NIR emission corresponding to ¹D₂ → ¹G₄ transition possesses a full-width at half-maximum (FWHM) of 210 nm. Although the obvious cross-relaxation (CR) process at high concentration causes a decrease of the quantum efficiency, the CR broadens the spectral FWHM effectively from another perspective. The admirable red fluorescence trace and the NIR single-mode transmission confirm that Pr³⁺ doped NMAG glass planar waveguides can support the generation of visible fluorescence and the amplification of infrared signal. For a waveguide channel ion-exchanged in molten KNO₃ for 2 h, the single-mode field diameters at 1.55 μm are identified to be 10.4 μm in the horizontal direction and 6.5 μm in the vertical direction, implying an acceptable overlap with a standard single-mode fiber. Effective red fluorescence and broad NIR emission demonstrate that Pr³⁺ doped NMAG glasses are a promising substrate in developing irradiative luminescence sources and ultra-broadband waveguide amplifiers, especially operating at the entire S-, C-, and L- bands.