Widely Tunable Narrow Linewidth Dual-Wavelength Yb-Doped Fiber Laser With Inhomogeneous Polarization Output

We demonstrate a widely tunable narrow linewidth dual-wavelength Yb-doped fiber laser with switchable inhomogeneous polarization output based on the Pancharatnam-Berry phase optical elements and volume Bragg grating experimentally. By rotating the Glan laser polarizer, we can obtain the switchable radially and azimuthally polarized beam with tunable wavelength separation ranging from 0.4 nm to 68.2 nm. The delivered spectrum shows excellent stability and linewidth narrower than 0.08 nm. Moreover, the polarization extinction ratio of the radially and azimuthally polarized beam can reach 94.2% and 93.6%, respectively. This tunable narrow linewidth dual-wavelength laser could enrich the manipulation potential of the fiber laser, and would benefit many applications like THz wave generation.