Affiliation:
1. Wuhan National Laboratory for Optoelectronics & School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
Abstract
We utilize a femtosecond laser-inscribed small-period long-period fiber grating (SP-LPFG) to induce a nonlinear polarization rotation (NPR) effect for mode-locking pulses in a normal dispersion erbium-doped fiber laser (EDFL). The SP-LPFG has a length of 2.5 mm and a period of 25 μm. At wavelengths of 1556 nm and 1561 nm, it exhibits polarization-dependent loss (PDL) values of 20 dB and 14.5 dB, respectively, sufficient to trigger the NPR mechanism. With the pump power increased to 500 mW, the laser achieves normal dispersion mode-locked pulses centered at 1575 nm in the L-band, with a 3 dB bandwidth of 1.35 nm and a pulse width of 1.61 ps. The radio frequency (RF) spectrum reveals an signal-to-noise ratio (SNR) of up to 63.6 dB, demonstrating the excellent stability of the laser operation. This SP-LPFG holds promising applications, paving the way for efficient, compact, and stable normal dispersion ultrafast fiber lasers.
Funder
National Key R&D Program of China
National Natural Science Foundation of China
Key R&D Program of Hubei Province