Linear cavity erbium-doped fiber laser employing PM-PCF based Sagnac loop comb filter for wavelength tunable laser generation

Abstract

A wavelength tunable linear cavity erbium-doped fiber (EDF) laser based on Sagnac loop incorporating with polarization-maintaining photonic crystal fiber (PM-PCF) was proposed and demonstrated experimentally. The Sagnac loop was composed of 0.5 m length PM-PCF, 1 × 2 optical coupler with 50:50 splitting ratio, and one polarization controller (PC). For the proposed fiber laser, the working threshold was 35 mW, the 3 m length EDF was used as gain medium, and 0.5 m length EDF was selected as saturable absorber to improve lasers stability. In the experiment, the comb filter effect was generated by Sagnac interferometer, and period was 2.52 nm. When the pump power was 150 mW, single-wavelength tunable laser output was realized within the range of 1528.73-1531.45 nm through adjusting PC, wavelength tuning interval was more than 0.58 nm, power difference was less than 3.681 dB, and signal to noise ratio (SNR) were higher than 31.101 dB. For the designed fiber laser, different groups of dualand triple-wavelength lasers output were obtained, the power difference was lower than 7.349 and 7.724 dB, and SNR was more than 31.752 and 38.623 respectively. The single-, dual-and triple-wavelength laser stability was test within 20 min, and power and wavelength fluctuation were 3.325 dB and 0.07 nm respectively.