Successive excited-state absorption through a multistep process in highly Er^3+-doped fiber pumped by a 148-μm laser diode

Abstract

The fluorescence spectra ranging from 400 to 1000 nm were investigated on highly Er(3+) -doped fiber pumped by a 1.48-microm laser diode. A strong green emission was observed. An investigation of the fluorescence intensity dependence on pump power revealed that the green emission is attributed to successive excited-state absorption through a three-step process and also that saturation of the atomic levels that contribute to the emission occurs.

Upconversion channels in Er3+:ZBLALiP fluoride glass microspheres

“…Notably, we have also observed emissions about 700 nm (T11). Previous Er 3+ emission at 700 nm has been attributed to the transition 4 F 7/2 → 4 I 13/2 following absorption of three pump photons at 1480 nm [34]. This seems unlikely in our case, since the JO theory suggests that a 492 nm emission would be more probable than a 700 nm emission from 4 F 7/2 .…”

Phonon‐assisted energy transfer in Er‐exchanged LiNbO 3

“…For this study, Z-and X-cut LiNbO 3 substrates (1-mm thin crystal plates) were immersed into a molten salt mixture (of Li 2 SO 4 : Na 2 SO 4 : K 2 SO 4 = 70.7 : 9.9: 19.4 wt%) containing 0.18 wt% of Er 2 (SO 4 ) 3 . In this way the surface nearby region were doped by Er⇔Li ionic exchange process.…”

“…near 1550 nm [1,2]. However, Er doping is known to lead to upconversion in most host materials (including LiNbO 3 ) [2][3][4], which is widely recognized as a gain limiting factor in Er-doped amplifiers [2,3]. General feature of all the upconversion mechanisms consists of phononassisted processes, providing both a high efficiency of nonresonant excited-states absorption [5] and excited-states repopulation through its selective nonradiative decay within either isolated Er 3+ ions [3,5] or clustered ones [4,5].…”

“…However, Er doping is known to lead to upconversion in most host materials (including LiNbO 3 ) [2][3][4], which is widely recognized as a gain limiting factor in Er-doped amplifiers [2,3]. General feature of all the upconversion mechanisms consists of phononassisted processes, providing both a high efficiency of nonresonant excited-states absorption [5] and excited-states repopulation through its selective nonradiative decay within either isolated Er 3+ ions [3,5] or clustered ones [4,5]. Thus, the upconversion can be suppressed by a proper choice of doping technology [2,3] and/or postdoping processing [4,6], which may provide as sufficient decreasing the relative concentration of clustered ions [3,4,6] as well as a strong alteration of electron-phonon coupling via variation either a lattice site of Er 3+ ion [4,5] or a phonon spectrum of host [2,5].…”

“…General feature of all the upconversion mechanisms consists of phononassisted processes, providing both a high efficiency of nonresonant excited-states absorption [5] and excited-states repopulation through its selective nonradiative decay within either isolated Er 3+ ions [3,5] or clustered ones [4,5]. Thus, the upconversion can be suppressed by a proper choice of doping technology [2,3] and/or postdoping processing [4,6], which may provide as sufficient decreasing the relative concentration of clustered ions [3,4,6] as well as a strong alteration of electron-phonon coupling via variation either a lattice site of Er 3+ ion [4,5] or a phonon spectrum of host [2,5]. In light of the wellestablished limitations [2,6] of Er indiffusion technique, Er exchange technique, inducing unusual chemical bonding rearrangement and evident crystal structure modification [7], appears to open the new possibilities for selective manipulation of phonon-assisted processes in Er:LiNbO 3 and, hence, for suppression of upconversion.…”