Up-conversion luminescence polarization control in Er3+-doped NaYF4 nanocrystals
Zhang Hui1, Yao Yun-Hua2, Zhang Shi-An2, †, , Lu Chen-Hui3, Sun Zhen-Rong2
       

Energy levels of Er3+ ions and possible pathways of green and red UC luminescences generated by a 1-kHz laser amplifier (a) and an 80-MHz laser oscillator (b).