KMnF₃:Yb³⁺,Er³⁺ Core-Active-Shell Nanoparticles with Broadband Down-Shifting Luminescence at 1.5 μm for Polymer-Based...

In this study, we prepared cubic-phase oleic-acid-coated KMnF₃: Yb³⁺,Er³⁺ nanoparticles (NPs) and NaYF₄:Yb³⁺,Er³⁺ NPs, which were about 23 nm. From the down-shifting emissions spectra of the two NPs obtained by 980 nm excitation, we observed the fact that the KMnF₃: 18%Yb³⁺,1%Er³⁺ NPs were a luminescent material with a broadband near-infrared emission of 1.5 μm, and full-width at half-maximum (FWHM) of 55 cm^-1, which was wider than that of the NaYF₄: 18%Yb³⁺,1% NPs. Therefore, we believe that the oleic-acid-coated KMnF₃:Yb³⁺,Er³⁺ NPs have great potential in fabricating broadband waveguide amplifiers. Through epitaxial growth of a KMnF₃: Yb³⁺ active-shell on the core NPs, we compounded KMnF₃:Yb³⁺,Er³⁺@KMnF₃:Yb³⁺ core-active-shell NPs whose 1.5-μm infrared emissions intensity was 3.4 times as strong as that of the core NPs. In addition, we manufactured waveguide amplifiers using KMnF₃:18%Yb³⁺,1%Er³⁺@KMnF₃:2%Yb³⁺ NPs as the core materials of the waveguide amplifiers. When the input signal power was 0.2 mW and the pump power was 200 mW, we achieved a relative gain of 0.6 dB at 1534 nm in a 10-mm long waveguide.