Wavelength and bandwidth tunable filter and its application in a dissipative soliton fiber laser

A wavelength and bandwidth tunable filter and its application in a dissipative soliton (DS) Yb-doped fiber laser are demonstrated. The spectral filter consisting of six cascaded temperature-sensitive long-period fiber gratings is designed and fabricated for the first time, to the best of our knowledge. The corresponding spectral characteristics of the filter are also characterized with temperature. Its 3-dB bandwidth can be adjusted from 4.84 to 11.02 nm, and the center wavelength is continuously adjustable from 1036 to 1045 nm. The sensitivity of the variation of the center wavelength and the linearity of the center wavelength variation are 32 pm/°C and 99.53%, respectively. This home-made spectral filter has two notable features: i) with regard to the tunable spectrum, the 3-dB bandwidth of the spectrum filter can be unchanged; ii) with regard to the spectral tunability, the 3-dB bandwidth of the spectral filter can also be quantitatively changed as needed by changing the heating mode. The home-made spectral filter is used in the DS fiber laser to further realize the continuous adjustment of DS with a tuning accuracy of 0.03 nm by a step size of 1°C. Such a wavelength-tunable DS fiber laser greatly enhances the design flexibility of the coherent anti-Stokes Raman scattering source.