3 $\mu$m Watt-Level All-Fiber Lasers Based on Mid-IR Dielectric-Coated Fiber Mirrors

We report watt-level mid-IR Dy
$^{3+}$
- and Er
$^{3+}$
-doped all-fiber lasers using highly resistant dielectric-coated fiber mirrors. The fiber pigtail mirror is specifically designed for dichroic operation (i.e. anti-reflection at 970–1200 nm pump wavelength and high-reflection around 3
$\mu$
m laser wavelength), and shows a high damage density of >5 MW/cm
$^{2}$
, which is favorable to high-power mid-IR laser operation. The Ta
${_{2}}$
O
${_{5}}$
monolayer protective film coated on ZBLAN fiber end-facet was used to mitigate the fiber tip photodegradation. Both of the compact all-fiber mid-IR cavities are formed by efficiently connecting the Dy
$^{3+}$
- and Er
$^{3+}$
-doped ZBLAN gain fibers with dielectric-coated fiber mirrors using the standard FC/PC fiber adaptor, respectively. An Er
$^{3+}$
: ZBLAN all-fiber laser at
$\sim$
2.80
$\mu$
m is achieved with a 5.697 W maximum output power and a slope efficiency of 32.4
$\%$
. Moreover, we realize a
$\sim$
2.93
$\mu$
m Dy
$^{3+}$
: ZBLAN all-fiber laser with the maximum output power of 1.148 W and a slope efficiency of 18
$\%$
, which is the highest output power of 1.1
$\mu$
m-pumped Dy
$^{3+}$
: ZBLAN fiber laser. This work may offer a promising way to the low-cost, miniaturized, high-power mid-infrared all-fiber laser.