Mechanical stabilization of a microrod-resonator optical frequency comb

We present line-spacing frequency control of a microresonator-based optical frequency comb by way of mechanical actuation. Using this novel technique, we have achieved a record level of residual stability in the line spacing of 5×10^-15 for 1s averaging. This demonstrates the potential of microresonator combs to support clocks with stability derived from optical frequencies. This work has been performed with newly developed microrod optical resonators fabricated by use of CO₂-laser machining.