In a groundbreaking advancement poised to redefine the landscape of acoustic physics and photonics, researchers have unveiled an ultrabroadband phonon laser frequency comb that surpasses the capabilities of prior acoustic frequency comb technologies. Unlike optical frequency combs, which have long been heralded for their precision in measuring and manipulating light, acoustic frequency combs operate within the domain of sound and mechanical vibrations. These combs manifest as a spectrum of evenly spaced frequencies, analogous to the uniform teeth on a comb, and hold immense potential for applications spanning precision sensing, imaging, metrology, and even biomedical ultrasonics.
Historically, the development of acoustic frequency combs has been constrained by significant technical limitations. Existing systems have operated predominantly at frequencies above 100 kHz—well beyond the range of human hearing—and have struggled to produce more than a few hundred discrete frequency components, or “teeth.” Such limitations curtail the resolution and breadth of applicability, hindering their use in complex scenarios requiring broader bandwidth and finer frequency granularity.
This new study, published in the esteemed journal Advanced Photonics, heralds a new era. The research team has engineered a phonon laser frequency comb that features up to 6,000 equidistant teeth, with a spacing tunable from as low as 10 Hz up to 100 kHz. This represents a monumental leap in both the tooth count and bandwidth tunability, firmly establishing a novel benchmark in the field. The collaborative effort spans the global scientific community, with contributors from China, Japan, India, Singapore, the United States, and the United Arab Emirates, underscoring its broad interdisciplinary appeal.
Central to this breakthrough is the innovative use of a phonon laser—a device that generates highly coherent mechanical vibrations analogous to the photon lasing process in optical lasers. The device’s heart is an ultrathin silicon nitride (SiN) membrane, approximately 100 nanometers thick, suspended within an optical cavity. This setup functions as a nano-scale mechanical drum where the membrane’s oscillations can be precisely controlled by light.
When laser light circulates inside the optical cavity, it exerts subtle radiation pressure on the silicon nitride membrane. As the laser power is gradually amplified, the radiation pressure intensifies, tightly coupling optical energy to the membrane’s mechanical motion. Beyond a critical threshold, this interaction transitions into the phonon lasing regime — characterized by highly organized, intense mechanical vibrations at defined frequencies and their harmonics. This state of phonon lasing is remarkable, as it mirrors the order and intensity of conventional optical lasers but in a vibrational, acoustic medium.
The resulting vibrations intricately modulate the cavity’s laser light, creating an intermediate optomechanical frequency comb. As the laser-membrane coupling deepens, nonlinear wave mixing among multiple vibrational modes emerges, transforming this intermediate comb into a fully developed phonon laser frequency comb. The innovation here is not merely the generation of a vast number of comb teeth but the dual existence of the comb in both mechanical (acoustic) and optical domains simultaneously. This unique dual-channel output capability was previously unattainable in acoustic frequency comb systems, positioning this technology at the forefront of both fundamental physics and practical applications.
By dramatically expanding the tunable bandwidth of frequency combs into regions covering from audible frequencies near 10 Hz up to ultrasonic ranges around 14 MHz, the research opens prospects for an array of cutting-edge technologies. Applications include underwater acoustic sensing with unprecedented resolution, structural health monitoring where acoustic waves detect flaws deep within materials, and advanced biomedical imaging techniques exploiting precise mechanical vibrations. The ability to finely control the frequency spacing extends the functionality of acoustic combs into realms traditionally dominated by optical systems.
However, current demonstrations operate under low-pressure vacuum conditions (up to 1 kPa) to minimize air damping that normally disrupts delicate mechanical oscillations. Operating at standard atmospheric pressure remains a formidable challenge, imperative for deploying these systems in everyday environments. Future developments are focused on integrating advanced nanofabrication methodologies such as dissipation dilution and metasurface engineering to enhance the mechanical quality factors of membranes and significantly mitigate air damping effects.
These improved fabrication techniques are expected to reinforce membrane stiffness while maintaining low mass, thereby preserving coherent phonon lasing even under ambient conditions. This adaptation could dramatically widen practical applications, ranging from environmental sensing to integration within compact photonics-on-chip technology platforms designed for harsh or complex operating conditions.
The implications of this ultrabroadband phonon laser frequency comb are profound. Beyond opening new research avenues in quantum mechanics and condensed matter physics, it provides a versatile platform for precise frequency control in devices previously limited by narrow acoustic bandwidths or minimal tooth counts. Its integration of light and sound at the nanoscale could inspire novel hybrid devices in optomechanics, sensor technology, and signal processing systems tailored for high sensitivity and selectivity.
This interdisciplinary research effort, led by Prof. Franco Nori and colleagues, not only pushes the envelope of what is technically feasible in generating and manipulating coherent phonons but also highlights the transformative potential of merging photonic and mechanical resonances. As the research community continues to explore the physical underpinnings and extend the technological readiness of such systems, the ultrabroadband phonon laser frequency comb may soon become a cornerstone technology across a spectrum of scientific and industrial domains.
In conclusion, this landmark study demonstrates an acoustic frequency comb with record-breaking tooth count and tunable span, harnessing phonon laser mechanisms within a silicon nitride membrane optical cavity. By transcending previous acoustic comb limitations and enabling simultaneous optical and mechanical frequency comb output, the research establishes a versatile, high-performance platform equipped to foster innovation in sensing, imaging, and beyond. The path forward will focus on overcoming atmospheric operation challenges through sophisticated nanofabrication techniques, heralding a new chapter in leveraging sound and light within miniature photonic devices.
Subject of Research: Not applicable
Article Title: Ultrabroadband phonon laser frequency comb
News Publication Date: 19-Feb-2026
Web References: https://www.spiedigitallibrary.org/journals/advanced-photonics/volume-8/issue-02/026004/Ultrabroadband-phonon-laser-frequency-comb/10.1117/1.AP.8.2.026004.full
References: G. Xiao et al., “Ultrabroadband phonon laser frequency comb,” Adv. Photon. 8(2), 026004 (2026), doi: 10.1117/1.AP.8.2.026004
Image Credits: G. Xiao et al.
Keywords
Acoustic properties, Quasiparticles
