Abstract
Abstract Optical clocks with unprecedented accuracy of 10−18 promise innovations in many research areas. Their applications rely to a large extent on the ability of precisely converting the frequency from one optical clock to another, or particularly to the frequencies in the fiber telecom band for long-distance transmission. This report demonstrates a low-noise, high-precision optical frequency divider, which realizes accurate optical frequency conversion and enables precise measurement of optical frequency ratios. By measuring against the frequency ratio between the fundamental and the second harmonic of a 1064-nm laser instead of a second copy of the same system, we demonstrate that the optical frequency divider has a fractional frequency division instability of 6 × 10−19 at 1 s and a fractional frequency division uncertainty of 1.4 × 10−21. The remarkable numbers can support frequency division of the best optical clocks in the world without frequency-conversion-caused degradation of their performance.
Highlights
Recent progress on optical atomic clocks demonstrates that the fractional frequency instability and uncertainty of optical clocks have been reduced to the 10−18 level [1−4]
Atomic and molecular spectroscopists hope that the frequency accuracy and high frequency stability of optical clocks can be transferred to a wide spectral range for high precision spectroscopy
optical frequency divider (OFD) can accurately convert the frequency from one optical clock with a preset division ratio to another, or to the frequencies in the fiber telecom band [25] or in the microwave region [26] for a wide range of applications
Summary
Recent progress on optical atomic clocks demonstrates that the fractional frequency instability and uncertainty of optical clocks have been reduced to the 10−18 level [1−4]. Using the OFD, the frequency ratios between optical clocks can be precisely measured without synchronous counting the beating frequencies between optical signals and a comb against a hydrogen maser.
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