energy exchange mechanisms in Yb:Ho:YAG crystals for 2 μm or 540 nm lasing

Multi-wavelength visible up-converted luminescence in novel heavily doped Ytterbium–Holmium silica fiber under low-power IR diode pumping

“…The powerful luminescence bands in the visible (Fig. 2) are an indication of an energy migration from the IRpumped sub-system of Yb 3+ to the sub-system of Ho 3+ that resembles the processes in other Yb-Ho systems [11][12][13][14][15][16][17][18][19]. Being non-perfectly resonant, this migration may be quite notable due to a wide range of an effective phonon's energy that holds for silica glass.…”

“…This choice of the co-dopants' concentrations was based on a study of preliminary-prepared fibers and the available data on optimal percentage of the co-dopants' in Yb-Ho-doped bulk crystals and glasses [10][11][12][13][14][15][16][17][18][19], which provides a maximum yield of visible luminescence at IR pumping.…”

“…Among them, silica fibers activated with holmium (Ho), or co-activated with Yb and Ho [4][5][6][7][8][9][10] are of a special interest since these fibers can be an alternative for communications purposes in a 2-mm spectral range and for the lidar and medicine applications. Yb-Ho-doped fibers can be also used as an amplifying medium for the frequency- On the other hand, as far as we know only the recent work [8] reports on an analysis of Yb-Hodoped silica fiber as a potential material for lasing at wavelength 2.1 mm at IR pumping, where the up-conversion mechanism [11], the effect wellknown in Yb-Ho-co-doped bulk crystals and glasses [12][13][14][15][16][17][18][19], is shown to be quite effective.…”

“…We show that the conventional mechanisms of energy migration from Yb 3+ to Ho 3+ and stepwise up-conversion within the Yb 3+ -Ho 3+ mixed system that is a consequence of a series of excited-state absorption (ESA) transitions are the processes highly effective in the Yb-Ho fiber as those in crystals [11][12][13][14][15][16][17][18][19]. We also discuss an avalanche-like character of the up-conversion process in the fiber and an additional channel of excitation of the Ho 3+ sub-system via an energy transfer from the Yb 3+ ion pairs [20][21][22][23].…”

The 1.2 and 2.0 μm Emission from Ho3+ in Glass Ceramics Containing BaF2 Nanocrystals

“…Compared with Tm 3+ , Yb 3+ offers some obvious advantages: its broad absorption band along with large absorption cross section at around 980 nm allows for compact laser systems pumped with commercially available high‐power InGaAs LD. Furthermore, it exhibits simple energy level diagram with only one excited energy level ( 2 F 5/2 ) lying at about 10 000 cm −1 above the ground state ( 2 F 7/2 ), which could reduce the incidence of multi‐phonon relaxation, excited‐state absorption, and direct Yb–Ho back transfer …”