High Gain Thulium-Doped Tellurium Oxide Waveguide Amplifier for Optical Communication in the $2-\\mu \\mathrm{m}$ Window

In this work, we present on a thulium-doped tellurium oxide (TeO2:Tm3+) waveguide amplifier on a silicon nitride (Si3N4) waveguide platform with 14.7 $\\text{dB}$ internal net gain at 1870 nm under 1607 nm pumping, corresponding to 2.96 dB/cm. Gain measurements were carried out in straight, paperclip and 5-cm-long spiral waveguides realized on a 1.0-cm-long chip. The device is fabricated using CMOS-compatible and wafer-scale processing steps, enabling compatibility with existing photonic integrated circuit (PIC) technology.