Optical Vapor Cell Iodine Frequency References for Space and Terrestrial Applications

Abstract

To improve the geolocalisation capabilities, next-generation GNSS has a demand for high-performance clock technologies outrunning the current microwave technologies. Optical frequency references based on modulation transfer spectroscopy (MTS) offer very low frequency instabilities in the 10E-14 .. 10E-16 range while keeping a comparably low SWAP and complexity, since they operate at room temperature and do not need a vacuum system. Together with an optical frequency comb, they form a fully functioning optical clock and are very promising candidates for next-generation GNSS clocks. To date, MTS of molecular iodine vapor offers the highest performance and is investigated in the Institute of Quantum Technology of the German Aerospace Center. These systems are quite well understood lab devices and have been tested on a sounding rocket (JOKARUS, [1]). At the moment, two activities are aiming to demonstrate this technology in orbit (COMPASSO @ DLR [2] as a payload at the ISS and a future space clock for autonomous operation at a MEO satellite). In this talk, we will show the current status of these space projects and highlight the performance achieved with the engineering models. As a second part of this presentation, we will highlight our work towards turnkey devices for terrestrial applications, since there is a growing demand for highly-stable ground-station frequency references and hold-over solutions for critical infrastructure under thread of GNSS jamming and spoofing. [1] Döringshoff et al. Phys. Rev. Applied 11, 054068 (2019). [2] Kuschewski et al. GPS Solut. 28:10 (2024).