Mode and Wavelength-Switchable Pulsed Fiber Laser With Few-Mode Fiber Grating

We propose and demonstrate a mode and wavelength-switchable pulsed fiber laser using two-mode fiber Bragg grating (TM-FBG) as both transverse mode converter and wavelength selector. The mode-locking mechanism is based on saturable absorption of semiconductor saturable absorption mirror (SESAM). Due to the use of low polarization-dependent mode-locking method, polarization disturbation between mode-locking and transverse-mode selection has been effectively eliminated, thus enabling flexible transverse-mode selection with simultaneous mode-locking operation. Moreover, through the optimized offset launching technique, this laser can operate at the wavelengths of the fundamental mode (LP01) and second-order mode (LP11), and thus export cylindrical vector beams (CVBs) and fundamental mode beams at the TM-FBG output port, respectively. This all-fiber laser is a simple, low-cost, and flexible source for mode-division multiplexing system and other applications.