We had proved that a kind of graphene nanomaterial “carboxyl-functionalized graphene oxide (GO-COOH)” possessed nonlinear saturable absorber (SA) property. The modulation depth of a GO-COOH water solution was measured as ∼8%. Moreover, a GO-COOH-based SA device was made and applied in an erbium-doped fiber laser. In this fiber laser, Q-switching pulses and mode-locked pulses were both obtained. With an increase in the pump power, the pulse width of Q-switching pulses decreased from 9.05 to 2.49 μs. The mode-locked pulse width was 844 fs, and the corresponding spectral bandwidth was 3.64 nm. Moreover, polarization adjusting or control was not needed during the whole process of mode locking. It illustrated that the proposed fiber laser incorporating GO-COOH could endure bigger intracavity birefringence. Our results indicated that the GO-COOH nanomaterial was a promising SA for generating high-performance pulse lasers.
The report proposed a saturable absorber based on a D-shaped fiber embedded in a single-walled carbon nanotube solution. Such a saturable absorber solution method with a D-shaped fiber has the virtues of good antioxidant capacity, excellent scattering resistance, high heat dissipation, and high damage threshold. The nonsaturable loss of this kind of saturable absorber was evaluated to be 3%. To the best of our knowledge, this is the lowest value compared with other carbon nanotube saturable absorbers. By incorporating the saturable absorber into a Yb-doped fiber laser cavity, a mode-locked fiber laser was achieved with a central wavelength of 1054.16 nm. The repetition rate was 23 MHz with a signal-to-noise ratio of 60 dB, and the pulse duration was measured to be 194 ps. The long-term working stability of working is also good. The results indicated that the solution method with a D-shaped fiber possesses a potential for fiber laser stability applications.
An all-normal dispersion passively mode-locked Yb-doped fiber laser with a Bi2Te3 absorber is presented. The modulation depth of this kind of saturable absorber was measured to be 8.4%. By incorporating a Bi2Te3/PVA film into a Yb-doped fiber laser oscillator, a mode-locked fiber laser oscillator was achieved. The repetition rate and the central wavelength are 25.6 MHz and 1052.7 nm, respectively. The 3-dB spectral width is 0.45 nm and the pulse duration is 417 ps. The results indicate that topological insulator Bi2Te3 possesses the potential for ultrafast fiber laser application.