Tuned cascade laser

Tuning of a diode-cladding-pumped cascade Ho3⁺ -doped fluoride fiber laser is demonstrated using a single plane ruled diffraction grating. At the maximum available pump power, a tuning range 2955-3021 nm, an output power of >500 mW, and a bandwidth of <1nm was achieved for tuning across the _⁵|₆ -> ⁵|₇ transition. In a separate experiment, the  _⁵|₇ -> ⁵|₈ laser transition was tuned from 2064 to 2082 nm (with a bandwidth of <0.5 nm) which simultaneously shortened the average emission wavelen _⁵|₆ -> ⁵|₇ length of the free-running  laser transition of the cascade from 2.959 to 2.954 µm. This demonstration represents the first fiber laser that can tune beyond 3 µm.