Radiation and gain behaviors in Tm³⁺-doped aluminum germanate substrate glasses and thermal ion-exchanged waveguide

Tm³⁺ -doped acid-resistant aluminum germanate (NMAG) glasses and a K⁺-Na⁺ ion-exchanged channel waveguide have been fabricated and characterized. Judd-Ofelt intensity parameters indicate a high asymmetry and strong covalent environment in NMAG glasses. A remarkable internal gain coefficient of 0.48 dB/cm at 1.482 μm wavelength was achieved in the 3.15 cm long channel waveguide. Based on absorption and emission cross-sections, the ideal internal gain coefficient at 1.675 μm and 1.815 μm is given to be 0.5 dB/cm and 2.0 dB/cm, respectively, as the population inversion equals 1.0. Experimental results and theoretical anticipation indicate that Tm ³⁺ -doped NMAG glasses are potential and attractive substrates in developing S- and U-band waveguide amplifiers and an eye-safe medical laser.