Telecommunication optical fibers can stabilize the laser frequencies to the quadrillionth level

Professor Jungwon Kim’s research team at KAIST has established a simple, compact, alignment-free, and potentially low-cost all-fiber photonic platform for generating multiple ultra-stable optical frequency combs, facilitating various applications ranging from telecommunications through molecular spectroscopy to quantum sensors.

Article | Fall 2020

Frequency-stabilized optical frequency combs have many high-precision applications. Accurate timing, ultra-low phase noise, and narrow linewidth are prerequisites for achieving the ultimate performance of comb-based systems. Ultra-stable cavity-based comb-noise stabilization methods have enabled frequency instability to the sub-10^-15-level; however, such state-of-the-art methods are highly complex and alignment-sensitive, and their use has been mostly confined to advanced metrology laboratories.

In a new report published in Science Advances, Professor Jungwon Kim’s research team at KAIST has established a simple, compact, and alignment-free all-fiber photonics-based platform for generating multiple ultra-stable optical frequency combs. The method is based on only off-the-shelf, telecommunications-grade fiber optic components, which enable both low cost and high reliability. Multiple combs with arbitrarily different repetition rates can be simultaneously stabilized to a compactly packaged 1-km-long standard telecommunication fiber spool with a diameter of only a few cm.

 

The achieved performance includes 1-fs timing jitter, 10^-15-level frequency instability, and <5-Hz linewidth, already rivalling those of state-of-the-art cavity-stabilized combs. This method also features high flexibility in configuration; as a representative example, two combs were stabilized with a repetition rate difference of 180 Hz and ~1-Hz relative linewidth and could be used as an ultra-stable, dual-comb spectroscopy source.

The demonstrated method constitutes a mechanically robust and reconfigurable tool for generating multiple ultra-stable combs that are highly suitable for various high-precision field applications. The potential application scope spans a wide spectrum, including molecular spectroscopy, photonics-based RADARs and LIDARs, time-of-flight (TOF) sensors, high-stability microwave generators for 5G and 6G telecommunication systems, and compact frequency stabilizer for atomic reference-based quantum sensors.

More information: D. Kwon et al. Generation of multiple ultrastable optical frequency combs from an all-fiber photonic platform. Science Advances 6, eaax4457 (2020).