Multi-Wavelength Upconversion Lasers Based on Coordination Polymer Glass Incorporating Lanthanide-Doped Nanoparticles

Upconversion microlasers hold great promise for next-generation photonic devices. Most current designs rely on coating or incorporating lanthanide-doped nanoparticles into dielectric microcavities, typically based on polymers or oxide glass platforms. However, polymers generally exhibit limited thermal stability, oxide glasses require relatively high processing temperatures, and coated structures often introduce interfacial scattering losses, degrading lasing efficiency and stability. Here, we report a coordination polymer (CP) ZnCl₂(bIm)₂ (bIm = C₇H₆N₂) glass as a low-temperature-processable host that enables uniform and nondestructive incorporation of upconversion nanocrystals via strong interfacial wettability, forming an energy barrier (2.52 × 10³ zJ) that preserves efficient luminescence, maintains high-Q characteristics, and supports ultrasmooth microcavity fabrication. To our knowledge, this work highlights the feasibility of multiwavelength upconversion lasing in transparent ZnCl₂(bIm)₂ composite glass micro-bottles embedded with NaYF₄@NaYbF₄: 1%Tm³⁺@NaYF₄ nanoparticles. Under continuous-wave 980 nm pumping, efficient lasing from the visible-to-near-infrared (NIR) region is achieved, featuring an ultra-low threshold of 140 nW for the Tm³⁺: ³H₄ → ³H₆ transition. Upconversion lasing is also generated in Er³⁺ and Ho³⁺-activated composite glass micro-bottles, highlighting the universality of this strategy. These findings establish a versatile platform for engineering lanthanide-based microlasers, paving the way toward compact, multifunctional photonic devices for next-generation optical technologies.