Abstract
A multi-wavelength thulium-doped fiber laser incorporating a photonic crystal fiber (PCF) Sagnac loop was presented and experimentally demonstrated. In the laser cavity, the Sagnac loop mirror used a 0.5 m PCF as a comb filter. A nonlinear polarization rotation (NPR)-based 600 m single-mode fiber (SMF) was used to suppress the mode competition. By adjusting the polarization controllers (PCs), up to nine stable wavelength outputs near the 2 μm spectrum were obtained at room temperature with an optical signal-to-noise ratio (OSNR) of up to 30 dB. The channel spacing of this fiber laser is 4.88 nm, and the 10 dB bandwidth encompasses 1950.39 to 1989.43 nm.
Highlights
T HULIUM-doped fiber lasers (TDFL) are of great interest due to their superior transmission and absorption properties
We propose a TDFL with a ring cavity structure, which uses high birefringent photonic crystal fiber (PCF) to make a Sagnac loop mirror while relying on the nonlinear polarization rotation (NPR) effect to suppress mode competition of the output wavelengths
When the light passes through the PCF, the phase difference between the fast axis and the slow axis will occur, and the direction of the polarized light will be rotated by an angle
Summary
T HULIUM-doped fiber lasers (TDFL) are of great interest due to their superior transmission and absorption properties. He et al proposed a Thulium-doped fiber laser based on a Sagnac ring and a Mach-Zehnder interferometer, which achieved a stable laser output from a single wavelength to a maximum of three wavelengths. Ahmad et al proposed an multimode fiber interferometer combined with a Sagnac ring thulium-doped fiber laser, which achieved stable output from a single wavelength to up to 9 wavelengths [11]. We propose a TDFL with a ring cavity structure, which uses high birefringent PCF to make a Sagnac loop mirror while relying on the NPR effect to suppress mode competition of the output wavelengths. By tuning the polarization controllers, the proposed all-fiber scheme allows stable multi-wavelength lasing oscillation with PCF-Sagnac at the near 2 μm spectral region.
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