Comparison of 10 MHz and an Optical Frequency with a 10− 18 Precision Level Using an Optical Frequency Comb

Abstract

We describe the recent developments in optical-to-microwave frequency comparison, which is the most fundamental application of an optical frequency comb. We focus on a comparison between 10 MHz and an optical frequency, which is needed to compare Coordinated Universal Time (UTC) with an optical clock. We report on the worldwide research situation, the precision limit conditions, and our achievement of a 10 MHz-to-optical frequency comparison with a 10− 18 precision level at NMIJ/AIST.