Development of VUV Laser technology
The latest value for the excitation energy of the thorium-229 first nuclear excited state is 8.338(24) eV, which corresponds to a laser wavelength required for its excitation of 148.71(47) nm. Therefore, the light is in the vacuum-ultra violet (VUV) regime, where laser technology is challenging. For the development of a nuclear optical clock one would ideally want to use a narrow-band cw laser, however, no such laser exists by today. One of the challenges that we are facing is the development of VUV cw laser technology with the goal to drive the Thorium-229 nuclear clock transition.
Laser target development
For laser spectroscopy of thorium-229, a thorium-229 target needs to be developed. We are investigating the concept of solid-surface spectroscopy, where a thin layer of thorium-229 atoms is irradiated. For that purpose, a Thorium-229 thin-film target, housed in an UHV chamber is being developed, which will later be used for laser spectroscopy experiments. In parallel, also different target concepts will be investigated.
Nuclear laser spectroscopy
It is the goal to do nuclear laser spectroscopy by combining the VUV laser technology and the thorium-229 target. For this reason the frequency of the laser will be measured with a frequency comb stabilized to a high-finesse cavity. Once the transition has been observed the combined system will act as a nuclear frequency reference.