Yangyang Du1,2, Yunfeng Wang3, Zhiqin Deng1,4, Xian Chen2, Xueqing Yang1,2, Tianying Sun1,2, Xin Zhang1,2, Guangyu Zhu1,4, S. F. Yu3, Feng Wang1,2
1City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, China
2Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong SAR, China
3Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR, China
4Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong SAR, China
Tóm tắt
AbstractDeep ultraviolet (UV) lasers are essential for enormous use ranging from medical and life science to environmental and industrial applications. Herein, a class of blue‐pumped microcavity lasers operating in the deep UV region is demonstrated by using Lu6O5F8:Pr/Gd@Lu6O5F8 upconversion nanocrystals as the gain medium. A hot‐injection synthesis is developed for tuning dimensions of the Lu6O5F8 nanocrystals. By synthesizing large‐sized nanocrystals and using inert shell coating, deep ultraviolet emission at 315 nm by blue excitation at 447 nm is realized for the first time in colloidal solutions. Mechanistic investigations suggest that the upconversion stems from sequential absorption of two blue photons by Pr3+ ions followed by energy transfer to Gd3+ emitters. By virtue of their small particle size and high dispersibility, the upconversion nanocrystals are readily incorporated into silica resin microcavities with a bottle‐like geometry. Lasing emissions of tunable optical characteristics are achieved from the microcavities through the formation of whispering gallery modes. These findings pave the way for constructing compact lasers operating in the deep UV regime by pumping with sophisticated long‐wavelength lasers.
