Wavelength switchable single-longitudinal-mode fiber laser with two π phase-shifted chirped fiber Bragg grating as a narrow linewidth filter

A wavelength switchable single-longitudinal-mode erbium-doped fiber laser is experimentally demonstrated, in which a novel two phase-shifted chirped fiber Bragg grating serves as the dual-channel narrow-linewidth filter, and a switch module consisting of three bandpass filters and a variable optical attenuator is used to control the laser behaviors of single- and dual-wavelength lasing. A stable dual-wavelength single-longitudinal-mode oscillation with 8-nm wavelength spacing is also realized and verified. The results provide a potential possibility to generate continuous terahertz waves optically.