2 μm fluorescence of Ho3+:5I7 → 5I8 transition sensitized by Er3+ in tellurite germanate glasses

• Er3+/Ho3+ co-doped tellurite germanate glass were prepared.
• The thermal stability, spectra properties and energy transfer mechanisms were investigated.
• The prepared glass possessed good stability.
• The FWHM of tellurite germanate glass reached as high as 146 nm.
• The stimulate emission cross-sections were calculated and discussed.

This paper investigated the mid-infrared luminescence properties of Er3+/Ho3+ co-doped tellurite germanate glass at 2 μm pumped by 980 nm. Thermal stability of the system, absorption spectra and fluorescence spectra of the Er3+/Ho3+ co-doped glass sample were measured. Besides, the absorption spectra of the Ho3+ singly doped sample was measured. According to the measured absorption spectra and the Judd–Ofelt theory, the Judd–Ofelt intensity parameters Ωt (t = 2, 4, 6), spontaneous radiative transition probability, branching ratio and lifetime of Ho3+ were calculated. And the upconversion emission in Er3+ doped and Er3+/Ho3+ co-doped tellurite germanate glasses pumped by 980 nm have been investigated. Then the spectroscopic properties and possible energy transfer mechanisms between Ho3+ and Er3+ ions were discussed in detail. Meanwhile, the FWHM (146 nm), σepeak × FWHM (659.92 cm3) and emission cross section (4.52 × 10−21 cm2) of 5I8 → 5I7 transition of Ho3+ were obtained, respectively. The results indicate that Er3+/Ho3+ co-doped tellurite germanate glass is a promising host material for 2 μm solid laser.

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