Spectral manipulation in a high-power ultrafast fiber laser system generating ultrashort pulses with GHz repetition rate

In this work, we demonstrate the spectral manipulation in an ultrafast fiber laser system that generates ultrashort pulses with a repetition rate of 1.2 GHz and two switchable modes — a 1064-nm fundamental laser mode with a maximum output power of 66.6 W, and a 1125-nm Raman laser mode with a maximum output power of 17.23 W. The pulse width, beam quality, and power stability are carefully characterized. We also investigate a method to switch between the two modes by manipulating the duty cycle of the modulation signal. It is anticipated that this bi-mode ultrafast fiber laser system can be a promising ultrafast laser source for frontier applications, such as micromachining, bioimaging, and spectroscopy.