Tm,Ho:(Y,Sc)2O3 Ceramic Laser at $\sim 2.1\ \mu \mathrm{m}$

Holmium ions (Ho
³⁺
) are interesting because of their emission in the eye-safe spectral range slightly above
$2\ \mu \mathrm{m}$
due to the
⁵
I
7
→
⁵
I
8
transition. Tm
³⁺
, Ho
³⁺
-codoping is frequently used for excitation of Ho
³⁺
ions: Tm
³⁺
ions (donors) efficiently absorb pump radiation at
$\sim 0.8\ \mu \mathrm{m}$
and non-radiatively transfer their energy to Ho
³⁺
ions (acceptors),
³
F
4
(Tm
³⁺
) →
⁵
I
7
(Ho
³⁺
). The codoping scheme also benefits from the combined gain bandwidths of both active ions which is attractive for broadband wavelength tuning and ultrashort pulse generation [1]. Cubic sesquioxides A
2
O
3
(where A = Y, Lu, Sc or their mixture) are the well-known host matrices for rare-earth doping. They can be elaborated in the form of transparent polycrystalline ceramics [2]. In the present work, we report on the first Tm, Ho:A
2
O
3
ceramic laser.