Tailoring the 4I9/2 → 4I13/2 emission in Er3+ ions in different hosts media

• The 4I9/2–4I13/2 emission band of Er3+ is potentially interesting for CH4 detection.
• Substituting S by O or Se does not spectrally shift this band but rather weakens it.
• The intensity of the 4I9/2–4I13/2 band varies significantly in powdered and bulk materials.
• Radiation diffusion explains this effect and is confirmed by Monte-Carlo simulations.

The 4I9/2–4I13/2 emission band of Er3+ is potentially interesting for CH4 detection because it can overlap with the optical absorption band of CH4. GaLaS and GeGaS glasses doped with Er3+ ions show the desirable emission under 808 nm excitation. An attempt of spectrally shifting 4I9/2–4I13/2 emission band by substituting S by O or Se to obtain a perfect match to the absorption band of CH4 leads to the weakening and disappearance of the 4I9/2–4I13/2 band. This phenomenon is tentatively related to the acceleration of non-radiative relaxation in the case of oxygen addition and to the suppression of up-conversion in the selenium substitution case. The relative intensity of the 4I9/2–4I13/2 band (with respect to the 4I13/2–4I15/2 band) varies significantly in powdered and bulk materials. This effect is discussed in terms of the radiation diffusion (i.e. radiation trapping) model and is confirmed by Monte-Carlo simulations.