Study on six-photon and five-photon ultraviolet upconversion luminescence

Enhanced ultraviolet up-conversion emissions of Tm3+/Yb3+ codoped YF3 nanocrystals

“…The experimental results are slightly different from those in Refs. [8,9]. In the Refs., the authors believed that populating the 1 D 2 level through cross relaxations (CR): 3 H 4 !…”

“…The introduction of Yb 3+ as a sensitizer at around 1 mm pumping wavelength, where high-power sources are commercially available, allows a large enhancement of UC fluorescence of lanthanide ion activators, too. In Yb 3+ sensitized rare earth ions doped materials, efficient IR (NIR)-to-UV UC emissions have widely been investigated [6][7][8][9]. Tm 3+ is a promising optical activator that provides the possibility for simultaneous blue and UV emissions of laser action and various applications [10][11][12][13][14][15].…”

Controlled synthesis and luminescence properties from cubic to hexagonal NaYF4:Ln3+ (Ln=Eu and Yb/Tm) microcrystals

“…The 1 D 2 level of Tm 3+ cannot be populated by the fourth photon from Yb 3+ via energy transfer to the 1 G 4 due to the large energy mismatch (about 3500 cm −1 ) between them [1]. The cross-relaxation process of 3 F 2 + 3 H 4 → 3 H 6 + 1 D 2 [21] as well as 1 G 4 + 3 H 4 → 3 F 4 + 1 D 2 [22] between Tm 3+ ions play an important role in populating 1 D 2 level. After populating the 1 D 2 level, the 1 I 6 level can be excited by another energy transfer process from Yb 3+ to Tm 3+ .…”

Synthesis and upconversion luminescence properties of YF3:Yb3+/Tm3+ octahedral nanocrystals

“…The experimental results are different from those in Ref. [16]. In this reference, the authors believed that six and five pumping photons were required to populate the 1 I 6 and 1 D 2 levels, respectively.…”