Optical clock technologies for global navigation satellite systems

Abstract

Future generations of global navigation satellite systems (GNSSs) can benefit from optical technologies. Especially optical clocks could back-up or replace the currently used microwave clocks, having the potential to improve GNSS position determination enabled by their lower frequency instabilities. Furthermore, optical clock technologies—in combination with optical inter-satellite links—enable new GNSS architectures, e.g., by synchronization of distant optical frequency references within the constellation using time and frequency transfer techniques. Optical frequency references based on Doppler-free spectroscopy of molecular iodine are seen as a promising candidate for a future GNSS optical clock. Compact and ruggedized setups have been developed, showing frequency instabilities at the 10–15 level for averaging times between 1 s and 10,000 s. We introduce optical clock technologies for applications in future GNSS and present the current status of our developments of iodine-based optical frequency references.

Short-term stability of Cs microcell-stabilized lasers using dual-frequency sub-Doppler spectroscopy

“…However, these instruments, making use of laser cooling, lattice-confined atoms or trapped ions, remain complex and their deployment outside the laboratory is challenging. To satisfy applications with stringent SWaP (size-weight-power) specifications, an attractive approach concerns the development of high-performance vapor cell-based optical clocks using Dopplerfree interrogation schemes [17]. In this domain, the two-photon transition at 778 nm in Rb vapor is an attractive candidate due to its narrow natural linewidth of about 300 kHz [18][19][20].…”

Electromagnetic Viscosity in Complex Structured Environments: From black-body to Quantum Friction

“…From the experimental point of view, our results will be of relevance for high-precision experiments with atoms, such as in the design of frequency references [77] or in the interpretation atom interferometric measurements [78], where black-body friction, e.g., can be connected to Stark shifts and modified atomic lifetimes [13,79]. Especially with the advent of miniaturization efforts in order to create portable devices of these emerging quantum technologies [80,81], the impact of the instrument's boundaries starts to matter and deviations from the simple Planck spectrum can become important [82,83]. For instance, if we take once again the simplest case of a rubidium atom moving in front of a single gold surface (described via the Drude model) at room temperature, the drag connected to the interaction with the surface starts to exceed the black-body vacuum drag below separations of some tenths of micrometers.…”

Tellurium Spectrometer for ${}^1\text{S}_0-{}^{1}\text{P}_1$ Transitions in Strontium and Other Alkaline-Earth Atoms

“…Recently, enthusiasm for these technologies has been driven by interest in a new generation of clocks for applications outside of the laboratory. Both two-photon rubidium 22 and molecular iodine 23 systems have advanced sig-nificantly and are being pursued for operations in space 24 .…”