2 μm Broadband Amplification in Tapered Fiber Devices Using PbS Quantum Dots

Broadband optical amplifiers operating in the 2 μm spectral region are critical for advancing mid-infrared photonic systems, yet achieving high gain with low noise remains challenging. In this work, we demonstrate a high-performance tapered fiber amplifier incorporating PbS quantum dots (QDs) as the gain medium. By optimizing the tapering geometry and QD doping concentration, we achieve a broadband on-off gain of >15 dB across a 200 nm bandwidth (1900–2100 nm). The unique combination of PbS QDs’ size-tunable bandgap and the tapered fiber’s enhanced evanescent field interaction enables efficient pump-probe overlap, resulting in a broader gain bandwidth compared to conventional rare-earth-doped fiber amplifiers. This work establishes a promising platform for compact, high-bandwidth mid-infrared light sources and amplifiers.