According to media reports on September 25， Professor Luo Hui and Associate Professor Xiao Guangzong’s research group from the National University of Defense Technology， in collaboration with Professor Jing Hui’s team， have successfully developed the first phonon laser frequency comb internationally. This groundbreaking achievement provides a high-precision new “acoustic ruler” for acoustic sensing applications such as underwater acoustic detection and biomedical imaging. The research results were recently published online in the journal Science Advances.
For comparison， the “optical ruler” – optical frequency comb technology – has long been widely used in optical measurement fields. In 2005， scientists John Hall and Theodor Hänsch were awarded the Nobel Prize in Physics for their contributions to optical frequency combs in precision spectroscopy and optical atomic clocks. Today， optical frequency combs have profoundly transformed various technological directions， including optical communication and optical ranging. However， their performance is limited in solid and liquid media.
In recent years， researchers have achieved phonon frequency combs based on thermal phonons. However， the lack of coherence between their “teeth” limits measurement accuracy. Professor Luo Hui aptly described this challenge: “It’s like using a ruler with blurred markings that constantly shakes， making precise measurements difficult.” Therefore， generating a phonon frequency comb with coherent “teeth” has become a key challenge in this field.
Phonon lasing is considered an effective path to overcome this challenge. As the “laser” in the field of mechanics， phonon lasing can produce highly consistent and coherent phonons， thus providing a basis for constructing coherent frequency combs. However， the realization of phonon laser frequency combs has long been technically elusive.
In 2023， this joint team published a paper in Nature Physics， successfully constructing a nonlinear phonon laser， laying the theoretical foundation for the generation of coherent phonon frequency combs. However， in practical implementation， challenges remained， such as limited “comb teeth” and difficulty in controlling their spacing.
In the latest research， the team introduced Floquet engineering into the nonlinear phonon laser system. By periodically modulating the pump signal， they effectively controlled and generated multiple coherent “comb teeth，” ultimately succeeding in fabricating a phonon laser frequency comb. Notably， this frequency comb possesses over 40 “comb teeth，” with significantly enhanced coherence and flexible adjustability of the “comb teeth” spacing.
Experts point out that this breakthrough technology is expected to find widespread applications in underwater detection， biomedical imaging， and quantum metrology， providing a novel tool for precision acoustic measurements.
