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

Abstract

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.

Phosphine Oxide-Nd3+ Coordination Chains with Cumulated Output Enable Efficient LED-Pumping Optical Amplification

“…In comparison to the previous reports of polymeric NDWAs, ,,,,,,− the optical gain performances at 1.06 μm of Nd2- doped devices with the maxima of 5.7 and 4.9 dB/cm exceed the maximum values of <4.0 dB/cm for most of inorganic NDWAs and especially NDWAs based on mononuclear Nd 3+ complexes (Figure f). So, it is rational that the one-dimensional chain structures of Nd1 and Nd2 indeed strongly enhance the low-power-pumping signal amplification through optimal intrachain energy transfer and migration to Nd 3+ ions for output accumulation, owing to the balance of host dispersion and local Nd 3+ centralization.…”

“…29 Most recently, we realized LED-pumping NDWAs using mononuclear Nd 3+ complexdoped polymeric gain media, which achieved relative gains of 2.0−3.0 dB/cm under a 405 nm LED pump with dozens or hundreds of milliwatts. 20,30 However, until now, only mononuclear lanthanide complexes were used for RDWAs. Obviously, despite waveguide structure optimization, e.g., evanescent-field configuration, 31−34 the gain effect obtained through mononuclear Nd 3+ complexes under LED pumping is still not satisfied.…”

“…Rare-earth doped waveguide amplifier (RDWA) is important for developing long-haul, multichannel optical communication systems because of its superiorities in output enhancement and loss reduction. − Compared to conventional fiber amplifiers, RDWA has the advantages of high lanthanide doping concentrations and small sizes, making it more easily integrated into compact optical systems. − Neodymium-doped waveguide amplifier (NDWA) is one of the most important RDWAs since Nd 3+ -doped media can realize continuous wave amplification at 1.06 μm optical window, originated from f - f transition of Nd 3+ ( 4 F 3/2 → 4 I 11/2 ), and effectively avert exciton annihilation in contrast to organic dyes. − Therefore, after the pioneer report of photolime gel:Nd 3+ based amplifier, NDWAs are developed rapidly in recent years. − Nonetheless, no matter in polymeric, sol–gel, or glass media, Nd 3+ ion concentrations of inorganic NDWAs were mostly limited to alleviate Nd–Nd interaction-induced quenching . As a result, for relative gains reaching ∼3 dB/cm, laser pumping was commonly under the power of hundreds of milliwatts, which not only hindered device miniaturization but also gave rise to upconversion-induced quenching of lanthanide ions and consequently thermal damage. , …”

“…This so-called ligand “antenna effect” allows lanthanide complexes to take use of ultraviolet (UV) and deep-blue light in the range of 200–450 nm for near-infrared (NIR) emissions, which actually establishes the basis for NDWAs using low-power UV-blue light-emitting devices (LEDs) as pump sources . Most recently, we realized LED-pumping NDWAs using mononuclear Nd 3+ complex-doped polymeric gain media, which achieved relative gains of 2.0–3.0 dB/cm under a 405 nm LED pump with dozens or hundreds of milliwatts. , However, until now, only mononuclear lanthanide complexes were used for RDWAs. Obviously, despite waveguide structure optimization, e.g., evanescent-field configuration, − the gain effect obtained through mononuclear Nd 3+ complexes under LED pumping is still not satisfied.…”

Boosting the Downconversion Luminescence of Tm3+-Doped Nanoparticles for S-Band Polymer Waveguide Amplifier

“…As an important and indispensable building block for integrated optical communication and light signal processing systems, optical waveguide amplifier has been widely used to compensate losses for maintaining information integrity during signal transmission. − In recent years considerable attention has been given to polymer optical waveguide amplifiers because of their low costs, simple processability, high bandwidth, excellent thermal stability, and easier integration over inorganic counterparts. − The S-band (Short-wavelength band) is one of the optical communication bands that covers the wavelength range 1460–1530 nm. As an essential and helpful complement to traditional C-band (Conventional band, 1530–1565 nm) and L-band (Long-wavelength band, 1565–1625 nm), the S-band can be applied for wavelength-division multiplexing (WDM) transmission to expand the transmission capacity by increasing the number of channels. − Despite their potential, the current development of the S-band waveguide amplifier is hindered by a number of limitations such as relatively scarce core materials, low power conversion efficiency, and poor gain performance.…”