by
Thomas Udem(Max Planck institute for quantum optics, Garching)
→
Europe/Stockholm
Oskar Klein Auditorium
Oskar Klein Auditorium
Description
A femtosecond frequency comb is a simple and compact tool that allows
the phase coherent connection of the radio frequency domain with the
optical domain. It greatly simplified high precision optical frequency
measurements of lasers and provides the long awaited clockwork mechanism
for an all-optical atomic clock. Another emerging application of
frequency combs is the calibration of conventional spectrographs for
high precision measurements that can not be performed by direct laser
excitation.
Maybe the most prominent examples are in astronomy where tiny Doppler
shifts of stars are used to detect the recoil motion caused by planets
in orbits. The current measurement accuracy is sufficient to detect "hot
Jupiters" but fails for Earth like planets. Very sensitive velocity
measurements are also required to directly probe the accelerating
expansion of the Universe. Observing the acceleration directly rather
than derive it from other observations assuming the validity of General
Relativity can be help to learn more about the nature and the existence
of dark energy.