Flexible Optical Amplifier for Visible-Light Communications Based on Organic-Inorganic Hybrids

Visible-light communications (VLCs) based on white light-emitting diodes (LEDs) are emerging as a low-cost and energy-efficient alternative solution to wireless communications. As white emitting LEDs use a combination of a long-lived yellow emission combined with the faster response of a blue emitting LED (∼460 nm), VLC technology requires amplification of the blue component to improve the signal-to-noise ratio. We report the fabrication and characterization of planar and channel waveguides based on a blue-emitting polyfluorene conjugated polyelectrolyte, namely, poly[9,9-bis(4-sulfonylbutoxyphenyl)fluorene-2,7-diyl-alt-1,4-phenylene] (PBS-PFP) incorporated into diureasil organic-inorganic hybrids for optical amplification in VLC. Taking advantage of the diureasil host as a UV self-patternable material, direct UV laser writing was used to pattern channel waveguides with a larger refractive index (Δn=0.09) compared to the nonexposed region, enabling confinement and guidance of the PBS-PFP emission with a maximum optical gain efficiency value of 1.62 ± 0.02 cm μJ^-1. This value is among the best figures of merit known for polymeric materials with additional advantages added by the diureasil hybrid host, namely, mechanical flexibility, thermal stability, and low insertion losses due to the nearly null refractive index contrast between the optical fiber and the amplification device, establishing the proposed approach as a promising cost-effective solution for optical amplification in VLCs.