Highly Efficient 2.84- $\mu \text{m}$ Emission in Ho3+/Yb3+ Co-Doped Tellurite–Germanate Glass for Mid-Infrared Laser Materials

The use of Yb
³⁺
co-doping with Ho
³⁺
to enhance the Ho
³⁺
:
⁵
I
₆
→
⁵
I
₇
~ 2.84-μm emissions is investigated in the tellurite-germanate glasses. An intense ~ 2.84-μm emission with a full width at half maximum (FWHM) of 132 nm is achieved in the Ho
³⁺
/Yb
³⁺
co-doped tellurite-germanate glass upon excitation at 980 nm. The glass not only possesses considerably low OH
^-
absorption coefficient (0.206 cm$^{-1}$ ), but also exhibits 2.84-μm large emission cross section (14.6 × 10
^-21
). Moreover, the measured lifetime of Ho
³⁺
:
⁵
I
₆
level is as high as 0.283 ms. Results reveal that Ho
³⁺
/Yb
³⁺
co-doped Tellurite-germanate glass is an attractive host for developing a mid-infrared 3-μm solid-state laser.