Chen Xb

Upconversion luminescence of ZBLAN:Tm 3+ ,Yb 3+ glass pumped by a ~970-nm LD and its concentration effect

Wide wavelength range of upconversion fluorescence at 360 nm, 450 nm, 475 nm, 647 nm, and 800 nm were observed in Tm3+ and Yb3+ codoped ZBLAN glass when pumped by a laser diode at approximately 970 nm. Those emissions are from three metastable states 1D2, 1G4 and 3F4, respectively. Three samples with varying Tm3+ and Yb3+ ion doping were investigated. It was shown that the luminescence intensity, as well as the dependence of intensity on laser power density, vary strongly with rare earth ion concentrations. And the mechanism for the population of 1D2 level is clarified further.

Dynamic up-conversion population processes of erbium-doped pentaphosphate crystal

Rate equations describing the dynamic processes in erbium (Er3+)-doped pentaphosphate crystals were developed to obtain the population processes of all levels of Er3+ ions in pentaphosphate ErP5O14 crystals under 650 nm laser excitation. The effects of pump power on the population (rho) dynamic process were analyzed. The spontaneous radiative processes, multiphonon nonradiative processes, absorption of the pump photons, corresponding stimulated radiation processes, and all other possible energy transfer processes between Er3+ ions were included in the rate equations. The pump power was assumed to be constant with time (t). Considering that the equation rho(t(0)+Deltat)=rho(t(0))+(drho/dt)Deltat would be held if Deltat was small enough and using the initial condition rho(1)=1.0, rho(i)=0(inot equal1), the time-dependent populations of all states could be obtained from the rate equations, from which the steady-state solution of the rate equation was deduced. The comprehensive study of the population dynamic process of all energy-level Er3+ ions in ErP5O14 crystal when excited by 100 mW-10(7) W has resulted in the conclusion that the strong upconversion luminescence would behave excellently when 650 nm pump laser power reaches the level of 1000-10(5) W. The representative population dynamic process when excited by 10(5) W laser power indicates I-4(15/2) and F-4(9/2) levels have a kind of great takeover co-contribution in up-converting population to higher states. The steady-state population probability of I-4(15/2) is as small as 0.0617. The population of the F-4(9/2) state increases rapidly to about a 0.362 high level and sequentially decreases smoothly to a stable value of about a 0.0374 low level, which implies a population already having been upconverted to higher level. Excellent results clearly exhibit that the main up-conversion luminescent level S-4(3/2) has a great population probability of about 0.212, which results in a strong up-conversion luminescence of 543 nm, and it is so exciting that a very strong 379 nm blue up-conversion luminescence could be achieved when 650 nm pump laser power is enhanced to the level of 1000-10(5) W. The results of this article are significant both to science and applications

Upconversion luminescence of Tm3+- and Yb3+-codoped pentaphosphate noncrystalline under the pumping of a 798-nm laser diode

When excited into Tm3 3F4 level by a LD at approximately 798 nm, Tm3 and Yb3 codoped pentaphosphate noncrystalline samples emit blue light at 475 nm, which corresponds to transition 1G4 yields 3H6. Although laser is directly absorbed by Tm3+ ions, the upconversion process rely on the codoping of Yb3+ ions. One Tm3+ yields Yb3+ transfer process excites Yb3+ ions, then backward Yb3 yields Tm3 energy transfer excites Tm3 ions from 3H4 to 1G4 level.