GHz fundamental repetition rate femtosecond Er:fiber laser mode locked by nonlinear polarization evolution

We demonstrate the first 1 GHz femtosecond erbium-doped fiber ring laser mode locked by nonlinear polarization evolution (NPE). The laser delivers a maximum average output power of 228 mW, correspondingly to single pulse energy of 0.228 nJ. The pulse spectral bandwidth is 32 nm, and the direct output pulse duration is 81.8 fs without extra-cavity compression. The integrated relative intensity noise (RIN) and the residual root mean square phase noise are measured to be 0.059% and 35 mrad (ranging from 10 Hz to 1 MHz), respectively. The result indicates that the high repetition rate lasers can operate without a significant increase in noise. This laser is an ideal source as a compact and relatively high pulse energy and short pulse at this repetition rate and shows great potential for optical frequency combs and other applications around 1560 nm wavelength.