Transverse mode switchable fiber laser through wavelength tuning.

We report a fiber laser design that is capable of producing switchable transverse modes through wavelength tuning. The transverse mode switching is realized by exploiting the particular transverse mode-wavelength association characteristics of the few-mode fiber Bragg grating. Different transverse mode outputs with high spatial mode quality can be obtained by adjusting the oscillating wavelength with a tunable filter within the fiber laser cavity. For each of the spatial mode outputs, the laser operates at the corresponding single wavelength with narrow linewidth. Through adding polarization controllers in the laser cavity, output modes with cylindrical vector polarization are also realized.