Photoinduced absorption in thulium-doped ZBLAN fibers

230 mW of blue light from a thulium-doped upconversion fiber laser

“…The observed effects are strongly reminiscent of earlier reports by several groups [7], [9], [11], [12] of a broadband induced loss, which is induced especially in fibers with high thulium concentration when pumped with wavelengths around 1120-1140nm. The exact mechanism of this effect is not yet known, but it is believed that the excitation of high lying levels of the thulium (above the G ) via energy transfer processes leads to the creation of color centers [9], [13].…”

“…It is interesting to note that a broad-band loss both in the blue spectral region and around 800nm was previously observed by us [9] in an earlier fiber from the same source (Le Verre Fluoré) as well as by another group [11], the latter using fibers from Galileo Electro-Optics Corporation; the new fiber used in the experiments we describe here (with slightly modified composition) as well as another fiber from Le Verre Fluoré (see [12]) again displayed the loss in the blue region but not around 800nm. Apparently there are two different kinds of color center, one of which has now been eliminated by a slight change of the fiber composition.…”

High-Power ZBLAN Glass Fiber Lasers: Review and Prospect

“…The loss induced in the visible region by 1140 nm radiation is very strong (as high as 25 dB in a 50 cm piece) and broadband. Laperle et al [149] found that the darkening rate is shown to follow a fourth-power dependence on the pumping intensity and a strong dependence on the Tm 3+ ion concentration. The photodegradation of upconversion Tm 3+ -doped ZBLAN fiber lasers was also observed [150].…”

“…It is believed that the excitation of higher levels of Tm 3+ ions via energy transfer processes leads to the creation of color centers that significantly increase the absorption in visible band. Although a few investigations of photodegradation and photobleaching have been conducted [149][150][151][152], so far there still has no effective method to prevent photodegradation occurring in high-power operation of Tm 3+ -doped ZBLAN fiber lasers. Nevertheless, using new pumping schemes [153][154][155][156] can improve the CW performance of Tm 3+ -doped ZBLAN fiber lasers by reducing the pump threshold and increasing the conversion efficiency.…”

Tm-doped aluminate glass fibers for S-band optical amplification

“…In order to improve the quantum efficiency of the desired fluorescence to practical levels, it is necessary to make TDFA fibers from Tm-doped glasses with MPE < $900 cm À1 [3]. Moreover, due to the tendency of Tm 3+ ions to upconvert to the higher lying 1 D 2 and 3 P 0 states, Tm-doped fibers may photodarken, resulting in significant optical losses in the near IR, when exposed to laser power levels typical of amplifier devices [2,4]. Consequently, transparency from the near IR to wavelengths <300 nm is another important attribute for TDFA host glasses.…”