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One of
the research directions aims at a metrology solution with ultra-high
stability and accuracy. The relative stabilities and accuracies of today’s
best clocks both enter into the range of 10-18, the optical
frequency comb as clockwork needs to keep pace. We present a fully phase-locked Er: fiber frequency comb system based on a new
oscillator design with a stability that even reaches 3∙10-18 within 1s which by far surpasses the stability of the best atomic clocks.
The
unparalleled accuracy provided by the regularly spaced lines (or modes) of
frequency combs opens up new pathways for astronomical spectrographs, such as
the detection of Earth-like extrasolar planets through radial-velocity
measurements or the direct observation of the accelerated cosmic expansion.
Recent successful applications include calibration of the HARPS spectrograph
at ESO’s La Silla observatory and KIS’ VTT spectrograph in Tenerife.
Comparison
of two different species of atomic clocks in zero gravity can test Einstein’s
general theory of relativity. The experiment with the Menlo optical frequency
comb has been launched on board the German Space Agency’s TEXUS 51 sounding
rocket mission from the Esrange Space Center on April 23, 2015 at 09:35 CEST
in Kiruna, Sweden. The clock comparison was successfully completed during the
entire zero gravity phase, demonstrating the robustness and high technology
readiness level of Menlo’s frequency combs, enabling future comb applications
on rockets, in space as well as in other harsh environments. At the same time,
this is the first demonstration of a fully operational frequency comb system
in space.
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