Lanthanide-doped nanocrystals in high-Q microtoroids for stable on-chip white-light lasers

Abstract

The plentiful energy states of lanthanide ( Ln 3 + )-doped nanomaterials make them very promising for on-chip integrated white-light lasers. Despite the rapid progresses, the Ln 3 + -based white upconversion emissions are strongly restricted by their low upconversion quantum efficiency and the color stability. Herein, we combine the CaF 2 : Yb 35 Tm 1.5 Er 0.5 nanocrystals and the high- Q microtoroids, and experimentally demonstrate the chip-integrated stable white-light laser. By optimizing the sizes, density, and distributions of Ln 3 + -doped nanocrystals, the Q factors of Ln 3 + -doped microtoroids are maintained as high as 5 × 10 5 . The strong light matter interaction in high- Q microtoroids greatly enhances the upconversion emission and dramatically reduces the laser thresholds at 652 nm, 545 nm, and 475 nm to similarly low values ( 1.89 – 2.10    mJ   cm − 2 ). Consequently, robust white-light microlaser has been experimentally achieved from a single microtoroid. This research has paved a solid step toward the chip-scale integrated broadband microlasers.