Amplifier-free erbium-fiber frequency comb

We demonstrate a self-referenced and optically-stabilized Er:fiber frequency comb that does not require external amplification. The 100 MHz frequency comb operates with only 250 mW of optical pump power. This advance employs a low-noise polarization-maintaining mode-locked laser that outputs 100 pJ, 100 fs pulses to drive octave generation and self-referencing with integrated nanophotonics. Multi-day optical phase locking and outdoor operation in the Colorado mountains highlight the robustness required for future use on transportable and airborne platforms beyond the research lab, where power and space are at a premium.