Optical gain at 1.55 µm of Er(TMHD) complex doped polymer waveguides based on the intramolecular energy transfer effect.

Based on the intramolecular energy transfer mechanism between organic ligand TMHD (2, 2, 6, 6-tetramethyl-3, 5-heptanedione) and central Er ions, optical gains at 1.55 µm were demonstrated in three structures of polymer waveguides using complex Er(TMHD)-doped polymethylmethacrylate (PMMA) as the active material. With the excitation of two low-power UV light-emitting diodes (LEDs) instead of 980 or 1480 nm lasers, relative gains of 3.5 and 4.1 dB cm were achieved in a 1-cm-long rectangular waveguide with an active core of Er(TMHD)-doped PMMA polymer. Meanwhile, relative gain of 3.0 dB cm was obtained in an evanescent-field waveguide with cross-section of 4 × 4 µm using passive SU-8 polymer as core and a ∼1-µm-thick Er(TMHD)-doped PMMA as upper cladding. By growing a 100 nm thick aluminum mirror and active lower cladding, the optical gain was doubled to 6.7 dB cm in evanescent-field waveguides because of the stimulated excitation of Er ions in the upper and lower cladding and the improved absorption efficiency.