Effect of CsBr addition on the emission properties of Tm 3+ ion in Ge-Ga-S glass
- PDF / 250,090 Bytes
- 8 Pages / 585 x 783 pts Page_size
- 32 Downloads / 155 Views
Absorption and emission properties of Tm3+ in (1-x) (Ge0.25Ga0.10S0.65)-xCsBr glass (x ⳱ 0.00–0.12) were investigated. Upon 10 mol% CsBr addition, the absorption cross sections of Tm3+ decreased accompanied by a large increase in the lifetime of the Tm3+:3H4 level to 1.23 ms since Tm3+ ions were surrounded by the Br ions of [GaS3/2Br]− units. As the concentration of Tm3+ increased, the 3H4 level lifetime decreased due to cross relaxation (Tm3+:3H4,3H6→Tm3+:3F4,3F4). Temperature dependence of the 3H4 level lifetime showed that cross relaxation in Tm3+ is a phonon-assisted energy transfer process. When Tm3+ were surrounded by Br ions, cross relaxation among Tm3+ was also suppressed due to a decrease in the transition probability among Tm3+ energy levels, a decrease in phonon energy of the host glasses, as well as an increase in the number of phonons participating in the cross relaxation process. The potential of Tm3+-doped Ge-Ga-S-CsBr glasses for S-band fiber amplifiers is also discussed.
I. INTRODUCTION
Tm3+-doped glasses have been investigated as alternative materials for fiber-optic amplifiers operating in the S-band (1460–1530 nm) communication window. It is known that the 1.48 m emission from the Tm3+:3H4→3H6 transition can provide a useful fluorescence for this wavelength band.1 However, it has been difficult to realize efficient amplifiers with glasses doped with Tm3+ because of the intrinsic difficulties associated with Tm3+. The lifetime of the terminal emission level (3F4) is 8–10 times longer than the lifetime of the 3H4 level. Thus, the population of excited Tm3+ ions stacked on the 3F4 level because of the low decay rate from this level to the ground state (3H6) that hampered the laser action.2 To achieve population inversion in Tm3+ ions, several methods have been proposed including co-lasing with the 3F4→3H6 transition,1,3 1.06 m up-conversion pumping2,4 and co-doping of Ho3+ or Tb3+ ions.5–7 In addition, non-radiative energy transfer processes such as multiphonon relaxation quenched the population density of the 3H4 level. The energy gap between the 3H4 level and the one located at immediately below (3H5) is approximately 4300 cm−1. Therefore, the population of the 3H4 level can be quenched through the stimulated emission of phonons.8 Fluoride glasses have mainly been
a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0278 J. Mater. Res., Vol. 21, No. 9, Sep 2006
http://journals.cambridge.org
Downloaded: 13 Mar 2015
used as Tm3+ hosts because of their low phonon energy.4,5,9 Furthermore, the lifetime and population density of the Tm3+:3H4 level also quenched via cross relaxation (3H4,3H6→3F4,3F4) by increasing Tm3+ concentration.10,11 Thus, the amount of Tm3+ in glasses must be kept low. Sulfide glasses also have been considered as host materials for Tm3+ since they have low phonon energy and good chemical properties.11,12 However, lifetimes of the 3H4 level in sulfide glasses were much shorter than those of fluorides because of the fast spontaneou
Data Loading...
