Future technologies for atom interferometry
Due to the band separation, GaAs optical waveguides become absorbent for laser wavelength below ~780nm and a material with higher excitation energies has to be utilized. The next choice would be GaN, which so far has mostly been used for novel electronic devices such as high-frequency transistors, but optical integrated device technology using this material is practically unexplored, with only a few preliminary studies iSense will investigate the possibility to create optical waveguides in GaN, which might be the foundation for future integrated optical devices working across the entire visible range. This would enable addressing of nearly all currently used atomic species and in particular extend the capabilities for sensors to Sr and Yb, which are candidates for future optical frequency standards of highest precision, surpassing current atomic clocks by three orders of magnitude.
Strontium and Ytterbium
Future GaN waveguiding and blue micro-integrated laser technology as pursued in iSense opens the choice to other interesting atoms for compact inertial quantum sensors, e.g. 88 Sr would be interesting due to its favourable properties of almost negligible cross section at ultra cold temperature and the insensitivity to magnetic field in the ground state. Exploiting these aspects one of our partners has already demonstrated coherence times in optical lattices with 88 Sr of the order of several seconds. A Bose-Einstein condensate of 88 Sr in 2009 marked an import breakthrough of a non interacting condensate with long coherence times. Furthermore, besides being discussed for quantum information applications, Strontium and Ytterbium isotopes having narrow-linewidth forbidden transitions in the visible spectrum are interesting candidates for precision frequency standards and are actively pursued for this purpose by several standard laboratories and metrology experts around the world. Moreover Yb provides several bosonic and fermionic isotopes that have already been driven to quantum degeneracy thereby offering a wide range of possible applications in high precision cold atom experiements. iSense will take into account the results form these investigations, e.g. in the broadening of its technological platform to GaN but also contribute novel aspects by the exploration of different isotopes as well as heteronuclear mixtures and experimentally determine their scattering parameters. These investigations will help to understand interactions and systematic effects involving these elements and thus help to advance frequency metrology applications using them.