High-performance, vibration-immune, fiber-laser frequency comb
Esther Baumann, Fabrizio R. Giorgetta, Jeffrey W. Nicholson, William C. Swann, Ian R. Coddington, Nathan R. Newbury
We demonstrate an environmentally robust optical frequency comb based on a polarization-maintaining, allfiber, figure-eight laser. The comb is phase locked to a cavity-stabilized cw laser by use of an intracavity electro-optic phase modulator yielding 1.6 MHz feedback bandwidth. This high bandwidth provides close to shot-noise-limited residual phase noise between the comb and cw reference laser of −94 dBc/Hz from 20 Hz to 200 kHz and an integrated in-loop phase noise of 32 mrad from 1 Hz to 1 MHz. Moreover, the comb remains phase locked under significant mechanical vibrations of over 1 g. This level of environmental robustness is an important step toward a fieldable fiber frequency comb.