The characteristic saturation phenomenon of upconversion luminescence in holmium–ytterbium-co-doped oxyfluoride glass Ho(0.1)Yb(5):FOG

Near white light emission of Ce3+‐, Ho3+‐, and Sm3+‐doped oxyfluoride silicate glasses

“…The emission bands which are ascribed to the ( 5 S 2 , 5 F 4 ) → 5 I 8 electronic transitions of Ho 3+ ions are observed in samples SFAC: 0.8H and SFAN: 0.8H . Sample SFAC: 0.8H shows an emission band centered at ~543 nm, however, the corresponding emission band of SFAN: 0.8H splits into two peaks, i.e., one centered at 538 nm and the other one at 548 nm, which are supposed to originate in the 5 F 4 → 5 I 8 and 5 S 2 → 5 I 8 transitions of Ho 3+ ions, respectively . The energy of the excited levels 5 F 4 and 5 S 2 of Ho 3+ ions is generally so close that the emission bands arising from the electronic transitions of excited states of 5 F 4 and 5 S 2 to the ground state 5 I 8 are almost superposed and difficult to distinguish.…”

“…5 I 8 transitions of Ho 3+ ions, respectively. 20 The energy of the excited levels 5 F 4 and 5 S 2 of Ho 3+ ions is generally so close that the emission bands arising from the electronic transitions of excited states of 5 F 4 and 5 S 2 to the ground state 5 I 8 are almost superposed and difficult to distinguish. However, this case is changed for sample SFAN: 0.8H.…”

Upconverted photoluminescence in Ho3+ and Yb3+ codoped Gd2O3 nanocrystals with and without Li+ ions

“…5. The upconversion luminescence of Ho 3+ single‐doped base materials is too weak to detect when excited by 976 nm photons (12). Therefore Ho 3+ ions cannot absorb 976 nm photons, and the upconversion mechanism of Gd 2 O 3 :Ho 3+ /Yb 3+ has to be the energy transfer from Yb 3+ to Ho 3+ .…”

“…Until now, Ho 3+ ion has been extensively investigated (5–11). For example, Tm:Ho solid‐state laser emitting in the eye‐safe region around 2 µm is a promising candidate for several applications, such as coherent Doppler velocimetry and high sensitivity DIAL measurements (5,10,12,13). Recently, due to Ho 3+ having a relatively long‐lived 5 I 7 level , which can act as a good population reservoir for the upconversion process, upconversion emission of Ho 3+ has been observed in several hosts involving bismuth tellurite glass and oxyflouride glass as well as YAl 3 (BO 3 ) 4 crystals (5,7,8,9,14).…”