Wavelength-Tunable High-Energy All-Normal-Dispersion Yb-Doped Mode-Locked All-Fiber Laser With a HiBi Fiber Sagnac Loop Filter

We experimentally demonstrate a broadly wavelength-tunable high-energy Yb-doped mode-locked fiber laser without any dispersion compensation. Wide tunability and filtering effect are simultaneously obtained using a fiber Sagnac loop filter in an all-fiber laser mode-locked by a semiconductor saturable absorber mirror. The Sagnac loop filter is constructed with a segment of a high birefringence (HiBi) fiber, a 3-dB coupler, and a polarization controller. By optimizing the HiBi fiber length and adjusting the polarization controller within the loop, the wavelength of the output pulse with 3 nJ pulse energy could be continuously tuned over the range from 1032 to 1052 nm. The heating of the HiBi fiber also led to wavelength shifting of the output pulse with a sensitivity of approximately
${-}{\rm 0.3}~{\rm nm}/^{\circ}{\rm C}$
.