Switchable soliton mode-locked and multi-wavelength operation in thulium-doped all-fiber ring laser

Abstract

A switchable soliton mode-locked and multi-wavelength operation in thulium-doped fiber laser (TDFL) is demonstrated based on nonlinear polarization rotation (NPR) technique. The TDFL produces a soliton pulse operating at 1917.66[Formula: see text]nm using a 5[Formula: see text]m long thulium-doped fiber (TDF) as a gain medium as well as nonlinear medium. The solitonic behavior is further identified with two orders of Kelly sidebands in the output spectrum. The mode-locked emission is obtained from threshold pump power of 522–1052[Formula: see text]mW with consistent pulse repetition rate of 14.7[Formula: see text]MHz. Maximum pulse energy is calculated as 0.89[Formula: see text]nJ at pump power of 1052[Formula: see text]mW, whereas the maximum pulse width is estimated to be approximately 1.36[Formula: see text]ps corresponding to sech2 pulse profile. By shifting the polarization orientation, the cavity can change to multi-wavelength operation with signal-to-noise ratio (SNR) higher than 53[Formula: see text]dB. At pump power of 1037[Formula: see text]mW, three stable peak wavelengths are generated with a power fluctuation and constant spacing of [Formula: see text] dB and 7.4[Formula: see text]nm, respectively.