Chelate phosphine oxide ligand (9,9‐dimethyl‐9H‐xanthene‐4,5‐diyl) bis (diphenylphosphineoxide) (XPO) is prepared as a neutral ligand to synthesize complex Nd (TTA)3 (XPO) (TTA = 2‐thenoyltrifluoroacetone). An appropriate energy gap between the XPO and TTA ligands, which can support two additional energy transfer routines from the first excited triplet state (T1) energy level of the XPO to that of the TTA, improves energy transfer in the Nd complex. Based on intramolecular energy transfer mechanism, optical gains at 1.06 and 1.31 µm are demonstrated in Nd (TTA)3 (XPO)‐doped polymer waveguides with the excitation of low‐power light‐emitting diodes (LEDs) instead of semiconductor lasers as pump sources. Using the vertical top‐pumping mode of a 365 nm LED, relative gains of 22.5 and 8.4 dB cm−1 are obtained at 1.06 and 1.31 µm, respectively, in a 0.2 cm long embedded waveguide with a cross‐section of 8 × 5 µm2. The active core layer is Nd (TTA)3 (XPO)‐doped SU‐8 polymer. Moreover, relative gains are achieved in evanescent‐field waveguide with a cross‐section of 6 × 4 µm2. The 21.0 and 5.6 dB cm−1 relative gains are achieved at 1.06 and 1.31 µm, respectively, with a net gain of 13.8 ± 0.3 dB cm−1 obtained at 1.06 µm in a 0.9 cm long SU‐8 waveguide with Nd (TTA)3 (XPO)‐doped polymethylmethacrylate as upper cladding.

Active Polymer Waveguides In article number 2209239, Hui Xu, Dan Zhang, and co‐workers report high gains at 1.06 and 1.31 μm wavelengths in a novel complex Nd (TTA)3(XPO)‐doped polymer waveguide with the excitation by light‐emitting diodes (LEDs) instead of a semiconductor laser as the pump source. The importance of this work is to minimize the commercial cost of waveguide amplifiers in planar photonic integration.