Broadband Packaged Erbium-Doped Polycrystalline Al₂O₃ Waveguide Amplifier with 24 dB External Net Gain

We present a packaged erbium-doped waveguide amplifier (EDWA) based on polycrystalline Al₂O₃, demonstrating high external fiber-to-fiber gain, stable performance over a broad wavelength range, and robustness to temperature variations. The device was integrated with fiber arrays and thermoelectric control, facilitating efficient characterization and practical deployment. With bidirectional pumping at 1480 nm, a 50 cm long waveguide amplifier achieves an external net gain of 24 dB and an off-chip output power exceeding 54 mW at 1550 nm. The amplifier exhibits a broad gain bandwidth, covering the entire C-band and extending into the L-band, with external net gain measured over a 90 nm span (1525 - 1615 nm). Temperature dependent measurements show that the amplifier maintains useful performance up to 95°C, with 17 dB of external net gain in the small-signal regime. These results highlight the potential of polycrystalline Al₂O₃:Er³⁺ as a scalable platform for high-performance optical amplification in photonic integrated circuits.