High Stability Harmonically Modelocked GHz Er Fiber Frequency Comb

Frequency combs are a key component of modern metrology, and becoming a building block of future photonics technology like telecommunications and optical computing. The repetition rate of a frequency comb has so far been determined by the size of the technology. Fiber lasers, the preferred workhorse of frequency combs, operate at about 250 MHz repetition rate, while small microresonators work at tens of GHz. However, it is not required to match the pulse rate to the free spectral range, but previous harmonically modelocked fiber lasers generally exhibited compromised stability and noise performance [1]. Here, we combine frequency combs and harmonic modelocking to generate a high stability 1 GHz repetition rate frequency comb from a 104 MHz free spectral range fiber laser.