Wavelength-tunable drop-shaped-cavity mode-locked Er-fiber laser

An ultrashort-pulse Er-fiber laser with an original drop-shaped cavity based on a dual-fiber optical collimator and a reflective diffraction grating was implemented for the first time. This new cavity allowed reliable passive mode locking as a classical all- fiber ring cavity but with an added benefit of continuous wide-range wavelength tuning. The tuning from 1527 nm to 1597 nm was demonstrated in the mode-locking regime. The new laser cavity has such advantages over tunable ring-linear fiber cavities as simplified design, reduced loss, and potentially shorter optical length.