High‐Gain of Nd^III Complex Doped Optical Waveguide Amplifiers at 1.06 and 1.31 µm Wavelengths Based on Intramolecular Energy Transfer Mechanism

Abstract

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.

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

“…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. , …”

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.…”