Er~(3+)-Yb~(3+) codoped fiber ring cavity passive harmonically mode-locked laser
The paper demonstrated that by using the nonlinear polarization rotation as the mode-locking mechanism,the laser could operate stably in either CW fundamental wave mode-locked or high-order harmonically mode-locked regimes by changing the pump power and adjusting the polarization controller.Under the pump power of 10 mW,fundamental wave mode-locked pulses with repetition rate of 15.89 MHz,output spectrum width of 9.9 nm,central wavelength of 1.557 nm was obtained.Under a different pump power of 75 mW,we obtained second harmonically mode-locked pulses with repetition rate of 31.79 MHz and third harmonically mode-locked pulses with repetition rate of 46.68 MHz.The paper also presented some preliminary theoretical analyses.