Effect of sample dimensions on observed photoluminescence from Er³⁺ ions in GeGaS and LaGaS glass hosts

The 4I9/2 - 4I13/2 emission band of trivalent Er3+ is potentially interesting light source for methane (CH4) detection because of its closeness to CH4 absorption band at 1.67 µm. In the present paper we report the influence of glass sample geometry on the shape of spectra and relative emission intensity of 4I9/2 - 4I13/2 band as well as three main 4I13/2 - 4I15/2 , 4I11/2 - 4I15/2 and 4I9/2 - 4I15/2 emission bands in sulfide glasses (GeGaS and LaGaS) doped with 0.5 at.% of Er. We show that the increase of sample size leads to a significant broadening of emission spectra as well as to the substantial suppression of 4I13/2 - 4I15/2 and 4I11/2 - 4I15/2 bands. The observed effects are explained by excitation diffusion or photon trapping (consecutive absorption and emission of light by Er3+ ions [1,2]) which turns out to be more effective in large samples. We present the results of Monte-Carlo simulations supporting our considerations and we discuss the possibility of increasing the 4I9/2 - 4I13/2 emission by controlling photon trapping

Tailoring the ⁴I9/2 -> ⁴I_13/2 emission in Er³⁺ ions

Many gas detection techniques rely on the absorption of light by specific absorption bands of the gas molecules. For example, methane (CH4) has two strong absorption bands around 3.3 and 1.67 µm. The latter band seems to overlap the 4I9/2 -> 4I13/2 emission band of trivalent Er3+, as shown in Figure 1; Er3+ is, of course, a popular rare-earth ion used various photonic device applications, including erbium doped optical fiber amplifier. In the present paper, we report that in some sulfide glasses (GeGaS and LaGaS) doped with 0.5 at.% of Er, the amplitude of 4I9/2 -> 4I13/2 emission band may reach up to 5% of the major 4I13/2 -> 4I15/2 emission band as shown in Figure 2. We investigate the possibility to "tailor" the 4I9/2 -> 4I13/2 emission band of trivalent Er3+ to better match the CH4 absorption band. In particular, we examined the possibility of spectral shift by using a nephelauxetic effect by substituting for sulfur with oxygen or selenium. Surprisingly, these substitutions suppress the 4I9/2 -> 4I13/2 emission band rather than shift it. The present paper also discusses the possible mechanisms for this suppression

THE INFLUENCE OF CSBR ADDITION ON OPTICAL AND THERMAL PROPERTIES OF GEGAS GLASSES DOPED WITH ERBIUM

The influence of the addition of CsBr on the optical and thermal properties of GeGaS glass doped with Er has been being investigated. We find that the addition of CsBr into GeGaS glass leads to some improvements in the radiative properties of Er3+ ions in this glass system. The GeGaS-CsBr glasses demonstrate much longer radiative lifetimes and stronger photoluminescence for I-4(13/2) -> I-4(15/2) and H-2(11/2) -> I-4(15/2) transitions in Er3+ ions. Very low Judd-Ofelt parameters and sharp Er3+ absorption spectra with multiple peaks suggest the presence of microcrystals. All optical parameters are strongly influenced by the interplay of Ga and CsBr. The glasses studied have been characterized by their basic glass transformation temperatures. The addition of CsBr into GeGaS glass keeping the ratio between CsBr and Ga close to unity is favorable for the incorporation of larger amount of Er. The experimental results are discussed in terms of structural local arrangement induced by CsBr addition.X111sciescopu

Observation of 4F3/2→4I15/2 radiative transition in Nd3+ ions in GaLaS glass using frequency-resolved PL spectroscopy

The photoluminescence (PL) emission band corresponding to 4F3/2 to 4I15/2 transition has been revealed using a double lock-in technique and quadrature frequency resolved spectroscopy (QFRS) at room temperature in Nd3+ in a GaLaS glass. The band is centred around 1840 nm and has a lifetime ~77µs, which seems to be the same for all four radiative transitions 4F3/2 to 4IJ (J = 9/2, 11/2, 13/2 and 15/2). The branching ratios β J of the four above transitions have been estimated from the PL data and agree well with the results of Judd-Ofelt (JO) analysis. In addition to the 1840 nm band, we have observed another PL band appearing around 1580 nm and having a dominant lifetime ~3.8 µs. This band may be identified with the radiative transition from the doublet (4F5/2, 2H9/2) to the 4I15/2 manifold. The short lifetime ~3.8 µs may be caused by effective multiphonon relaxation from the doublet to the 4F3/2 manifold

Observation of ⁴F_3/2 to ⁴I_15/2 radiative transition in Nd³⁺ ions in GaLaS glass using frequency-resolved PL spectroscopy

The photoluminescence (PL) emission band corresponding to 4F3/2 to 4I15/2 transition has been revealed using a double lock-in technique and quadrature frequency resolved spectroscopy (QFRS) at room temperature in Nd3+ in a GaLaS glass. The band is centred around 1840 nm and has a lifetime ~77µs, which seems to be the same for all four radiative transitions 4F3/2 to 4IJ (J = 9/2, 11/2, 13/2 and 15/2). The branching ratios β J of the four above transitions have been estimated from the PL data and agree well with the results of Judd-Ofelt (JO) analysis. In addition to the 1840 nm band, we have observed another PL band appearing around 1580 nm and having a dominant lifetime ~3.8 µs. This band may be identified with the radiative transition from the doublet (4F5/2, 2H9/2) to the 4I15/2 manifold. The short lifetime ~3.8 µs may be caused by effective multiphonon relaxation from the doublet to the 4F3/2 manifold