Temperature-dependent tunable spectral filters and their applications in fiber lasers

We designed and fabricated a temperature-dependent tunable filter based on cascaded long-period fiber gratings (LPFGs). Through the novel design, six LPFGs are concatenated together to realize the center wavelength, and the filter's bandwidth can be precisely adjustable only by controlling the temperature. Furthermore, an unprecedented performance is that the pulses do not experience the process of losing mode-locking to establishing mode-locking during the wavelength and bandwidth tuning procedure. It can realize two different tunings. First, 3-dB bandwidth remains unchanged while the spectrum's adjustment; second, it quantitatively changes through different heating modes. Such a flexible filter can also adopt in a Mamyshev oscillator to construct a curial part for self-starting and exploring relevant dynamic characteristics.