Optical gain at 1.55 µm of Er(TMHD)3 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 Er3+ ions, optical gains at 1.55 µm were demonstrated in three structures of polymer waveguides using complex Er(TMHD)3-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-1 were achieved in a 1-cm-long rectangular waveguide with an active core of Er(TMHD)3-doped PMMA polymer. Meanwhile, relative gain of 3.0 dB cm-1 was obtained in an evanescent-field waveguide with cross-section of 4 × 4 µm2 using passive SU-8 polymer as core and a ∼1-µm-thick Er(TMHD)3-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-1 in evanescent-field waveguides because of the stimulated excitation of Er3+ ions in the upper and lower cladding and the improved absorption efficiency.

Optical Amplification at 1.5 µm in ErIII Coordination Polymer-Doped Waveguides Based on Intramolecular Energy Transfer.

9,9-bis (diphenylphosphorylphenyl) fluorene (FDPO) and dibenzotetrathienoacene (DBTTA), are synthesized as the neutral and anionic ligands, respectively, to prepare the ErIII 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 ErIII 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.

High-Gain of NdIII Complex Doped Optical Waveguide Amplifiers at 1.06 and 1.31 µm Wavelengths Based on Intramolecular Energy Transfer Mechanism.

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.

Optical Amplification at 637 and 1067 nm Based on Organic Molecule AQ(PhDPA)2 and NdIII Complex Codoped Polymer Waveguides.

Based on the molecular energy transfer mechanism, relative gains at 1067 and 637 nm wavelengths are achieved in thermally activated delayed fluorescence molecule AQ(PhDPA)2 and Nd complex with chelating phosphine oxide as ligands codoped polymer waveguides, with the excitation of low-power UV light-emitting diodes (LEDs) instead of traditional semiconductor lasers as pump sources. For AQ(PhDPA)2 -Nd(DBTTA)3 (DBFDPO) (DBTTA = dibenzotetrathienoacene, DBFDPO = 4,6-bis (diphenylphosphoryl) dibenzofuran) -codoped polymethylmethacrylate (PMMA), and AQ(PhDPA)2 -Nd(DBTTA)3 (FDPO) (FDPO = 9,9-bis (diphenylphosphorylphenyl) fluorene)-codoped PMMA polymers with a mass ratio of 1:4 respectively, when they are spin-coated as upper claddings, the relative gains of 2.2 and 1.8 dB cm-1 at 1067 nm are obtained in evanescent-field waveguides with cross-section of 4 × 8 µm2 under excitation of 300 mW 405 nm LED, and the gains of 3.9 and 4.9 dB cm-1 at 637 nm are achieved with pumping of 530 mW 450 nm LED respectively. By growing a 100 nm-thick aluminum reflector with the waveguides, the optical gain at 1067 and 637 nm can be enhanced to 3.5 and 6.1 dB cm-1 , corresponding to AQ(PhDPA)2 -Nd(DBTTA)3 (DBFDPO) and AQ(PhDPA)2 -Nd(DBTTA)3 (FDPO)-codoped PMMA polymers, respectively.

5-Channel Polymer/Silica Hybrid Arrayed Waveguide Grating.

A 5-channel polymer/silica hybrid arrayed waveguide grating (AWG), fabricated through a simple and low-cost microfabrication process is proposed, which covers the entire O-band (1260-1360 nm) of the optical communication wavelength system. According to the simulation results, the insertion loss is lower than 4.7 dB and the crosstalk within 3-dB bandwidth is lower than ~-28 dB. The actual fiber-fiber insertion loss is lower than 14.0 dB, and the crosstalk of the 5 channels is less than -13.0 dB. The demonstrated AWG is ideally suitable for optical communications, but also has potential in the multi-channel sensors.