Program

Abstract:

Laboratory optical atomic clocks are now capable of reaching 1E-18 timing instability [1]. Such performance could support meter-scale positioning (< 3 ns) for ~ 100 years without external resynchronization. However, despite demonstrable performance improvements, optical clocks have yet to be deployed in commercial or defense systems. Current-generation optical clocks come with large and costly overhead, including lasers and optics, ultra-high vacuum (UHV) systems, and complex electronics. Such clocks operate in challenging wavelength ranges (400-800 nm) and generally do not leverage commodity components (switches, modulators, isolators, etc.) developed for common wavelengths (e.g., 1064 nm and 1550 nm). Recently, Vector Atomic has developed and fielded simplified iodine optical atomic clocks for operation outside of the laboratory. The clocks employ a robust vapor cell architecture that uses no consumables, requires no laser cooling or trapping, and is insensitive to platform motion. Importantly, the clocks utilize high-TRL laser components at 1064 nm developed for industrial machining and LIDAR. Focusing on a robust laser system rather than a high-performance atomic species (e.g., Sr or Yb) resolves critical issues with cost, dynamics, lifetime, and autonomy. While not as accurate as current laboratory optical clocks, iodine clocks can provide maser-like performance in a compact package [2-4]. The core clock subsystems, including the spectrometer, laser system, and frequency comb, were purpose-built in-house to reduce system-level size, weight, and power (SWaP). Initial clock prototypes have been integrated in 35 L rackmount chassis for real world testing. Software has been developed for rapid start-up and long-term, autonomous operation. Here we report test results from our first two offsite clock demonstrations. First, two clocks were operated continuously at NIST-Boulder for 30+ days, with performance characterized versus Coordinated Universal Time (UTC) [5]. Next, three clocks were operated continuously at-sea for 20+ days. In both cases, no special measures were taken to control the operating environment. Nevertheless, without any drift correction, our clocks’ long-term timing error holds below 1 ns for more than 3 days. Such performance compares favorably to masers, which typically operate in large (~1,000 L) environmental chambers as well as cesium beam clocks, which accrue 1 ns of error in ~12 hours.