Optical Amplification at 1.5 µm in Er^III Coordination Polymer-Doped Waveguides Based on Intramolecular Energy...

9,9-bis (diphenylphosphorylphenyl) fluorene (FDPO) and dibenzotetrathienoacene (DBTTA), are synthesized as the neutral and anionic ligands, respectively, to prepare the Er^III coordination polymer [Er(DBTTA)₃(FDPO)]_n. Based on the intramolecular energy transfer, optical gains at 1.5 µm are demonstrated in [Er(DBTTA)₃(FDPO)]_n-doped polymer waveguides under excitations of low-power light-emitting diodes (LEDs) instead of laser pumping. A ligand-sensitization scheme between organic ligands and Er³⁺ ions under an excitation of an ultraviolet (UV) LED is established. Relative gains of 10.5 and 8.5 dB cm^-1 are achieved at 1.53 and 1.55 µm, respectively, on a 1-cm-long SU-8 channel waveguide with a cross-section of 2 × 3 µm² and a 1.5-µm-thick [Er(DBTTA)₃(FDPO)]_n-doped polymethylmethacrylate (PMMA) as upper cladding. The Er^III coordination polymer [Er(DBTTA)₃(FDPO)]_n can be conveniently integrated with various low-loss inorganic waveguides to compensate for optical losses in the C-band window. Moreover, by relying on the intramolecular energy transfer and UV LED top-pumping technology, it is easy to achieve coupling packaging of erbium-doped waveguide amplifiers (EDWAs) with pump sources in planar photonic integrated chips, effectively reducing the commercial costs.