Broadband 2 μm amplified spontaneous emission of Ho/Cr/Tm:YAG crystal derived all-glass fibers for mode-locked fiber laser applications

Broadband ∼2  μm amplified spontaneous emissions with a full width at half-maximum (FWHM) varying from ∼206 to ∼234  nm were obtained from the Ho/Cr/Tm:yttrium aluminum garnet (YAG) crystal derived fibers, which were drawn using a molten core method. The core-cladding structure of the as-drawn fibers was preserved completely, and the core was found to be amorphous. What is more, an all-fiber-integrated passively mode-locked laser based on an 8 cm long Ho/Cr/Tm:YAG crystal derived all-glass fiber was built which, to the best of our knowledge, is the first demonstration of a mode-locked fiber laser in a similar YAG derived fiber. The mode-locked pulses operate at 1.95 μm with duration of ∼118  ps, and the repetition rate is ∼9.5  MHz. Limited by the bandwidth of the fiber grating used in the laser cavity, the mode-locking spectrum has a relatively narrow FWHM of ∼0.09  nm. These results suggest that the broadband YAG crystal derived all-glass fibers are promising for ultrafast fiber lasers applications.