Thermalization effects between upper levels of green fluorescence in Er-doped silica fibers

Abstract

We present a spectroscopic study of the green fluorescence resulting from pump excited-state absorption in Er-doped silica fibers excited in the 800-nm range. The absorption and emission bands are selectively attributed to the (4)S(3/2) and (2)H(11/2) levels. The fluorescence response at two excitation wavelengths, the temperature behavior, and lifetime measurements demonstrate a fast thermalization between the (4)S(3/2) and (2)H(11/2) levels. This explains an important part of the (2)H(11/2) emission and the increase of the fluorescence intensity at high temperature.

Sensitivity of a temperature sensor, employing ratio of fluorescence power in a band

“…The energy gap between them (about 800 cm À1 ) is relatively small in comparison with the energy difference between them and the next lower level of 3000 cm À1 . In silica, a fast thermal coupling between these two levels has been explained theoretically [6] and confirmed experimentally [7].…”

“…1 (after Ref. [7]). We changed the abscissa to show the spectral power in (nW/ nm), rather than intensity (the established terminology for this field).…”

Optical Fiber Sensors: An Overview

“…An extensive review of rare-earth doped optical fiber sensors based on the fluorescenceintensity ratio technique is given in the references at the end of the chapter (CastrellonUribe, 1999(CastrellonUribe, , 2002a(CastrellonUribe, , 2002b(CastrellonUribe, , 2005(CastrellonUribe, , 2010Dos Santos et al, 1999;Imai & Hokazono, 1997;Maurice, 1994Maurice, , 1995aMaurice, , 1995bMaurice, , 1997aMaurice, , 1997bWade , 1998Wade , 1999aWade , 1999b.…”

“…The latter levels were said to be in quasi-thermal equilibrium because of the small energy gap between them (about 800 cm -1 = 1.59x10 -20 J) in contrast to the relatively large energy difference between them and the next lowest level (about 3000 cm -1 = 5.9636x10 -20 J). In silica, a fast thermal coupling between these two levels has been studied theoretically and observed experimentally (Berthou & Jorgensen, 1990;Krug et al, 1991;Maurice, 1994. The ratio, R, of the intensities, I, radiating from two respective levels ( 2 H 11/2 and 4 S 3/2 ) was proportional to their frequency ratio (ν), their emission cross-section ratio (σ), and the population distribution: Figure 6 shows the experimental setup that was used to evaluate the performance of the erbium-doped silica fiber sensor for remote temperature measurements.…”

Er3+-Yb3+ codoped borosilicate glass for optical thermometry

“…Among a number of optical temperature sensors that have recently been presented, the most outstanding approach is based on the fluorescence intensity ratio (FIR) technique [7][8][9][10][11], which can help reduce the influence of measurement condition and therefore, improve the measurement sensitivity. Some previous works on optical temperature sensors using the FIR technique from green up-conversion emissions of Er 3+ have mainly focused on fluoroindate and chalcogenide glasses [10,11], but which can operate only at temperatures below 523 K because of their lower chemical durability and thermal stability.…”