High Gain of O+C Broadband Amplification Based on PbS/CdS Colloidal Quantum Dots‐Doped Waveguide under LED Pumping

ABSTRACT PbS/CdS core–shell colloidal quantum dots (CQDs) with average diameters of ∼5.6 ( CQDs 1 ) and ∼3.4 nm ( CQDs 2 ) are co‐doped to produce hybrid CQDs 3 , which are subsequently doped in polymethyl methacrylate (PMMA) to serve as a broadband optical gain medium. Optical amplification is observed across both O and C bands. Relative gains of 25.3 dB at 1550 nm and 21.3 dB at 1310 nm are achieved using a 3‐cm‐long SU‐8 polymer waveguide with a 2 × 3 µm ² cross‐section. An ∼1.6‐µm‐thick CQDs 3 ‐doped PMMA upper cladding is utilized, and two low‐power ultraviolet light‐emitting diodes are employed as pump sources instead of a conventional 980 nm laser. For SU‐8 polymer, silicon nitride, and BK7 glass waveguides utilizing CQDs 3 as the gain medium, average relative gains in the C band (1528–1568 nm) are 12.1, 9.5, and 3.8 dB/cm, respectively. In the O band (1270–1370 nm), they are 10.8, 9.9, and 3.7 dB/cm, with a gain ripple maintained below 4 dB. This work presents a cost‐effective and broadband loss‐compensation strategy compatible with both organic and inorganic photonic platforms for planar integrated circuits. This strategy effectively mitigates the thermal quenching effects associated with high‐power laser pumping.