Tunable multi-wavelength thulium-doped fiber laser based on Sagnac ring filter

A thulium-doped fiber laser incorporating with Sagnac ring filter is proposed, in order to realize a tunable multi-wavelength laser output. In designed ring cavity fiber laser, one broadband reflection mirror with metal-coated is selected as wavelength reflector, and Sagnac loop is composed of 4 m long polarization maintaining fiber and one 3 dB coupler, and one polarization controller is used to adjust laser wavelengths. In the expriment, the lasing threshold is 150 mW, a tunable and stable single wavelength laser can be realized, and the minimal tunable laser interval is 2 nm; when 1843 nm laser is obtained, the peak power fluctuation is less than 1 dB within 10 min monitor time. By adjusting polarization controller, a tunable dual-wavelength laser can be realized, when 1845 and 1854 nm lasers are achieved simultaneously, the peak power shift is less than 0.8 dB within 10 min scan time at room temperature, and the power difference value of each dual-wavelength laser is less than 3.81 dB. When a tunable triple-wavelength laser is realized through changing polarization state, the power difference value of each lasing is less than 4.1 dB; when four-wavelength and five-wavelength lasing are obtained, the maximum power difference is less than 2.807 and 2.929 dB. In the experiment, the laser 3 dB linewidth is less than 0.4 nm, and side-mode suppression ratio is greater than 32.4 dB. This electronic document is a “live” template and already defines the components of your paper [title, text, heads, etc.] in its style sheet.