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

The interaction of electrons with magnetic fields has long been a fascinating aspect of condensed-matter physics, leading to remarkable phenomena such as the quantum Hall effect and the formation of discrete energy levels. However, unlike charged particles, light is composed of neutral photons that do not interact with magnetic fields in the same manner. This fundamental distinction has posed significant challenges in replicating magnetic effects in optical systems, especially at the high frequencies required for modern telecommunications.

In this remarkable study, scientists have successfully addressed these challenges by engineering pseudomagnetic fields—synthetic fields that replicate the effects of real magnetic fields—within nanostructured materials known as photonic crystals. This research, detailed in the esteemed journal Advanced Photonics, presents a significant shift in our understanding of how light can be manipulated using artificial gauge fields.

The essence of this accomplishment lies in the systematic alteration of the symmetry in tiny repeating units found within the silicon photonic crystals. By precisely adjusting the local asymmetry at each point, researchers were able to design pseudomagnetic fields featuring specific spatial patterns. This innovative method preserves the fundamental time-reversal symmetry while allowing for unprecedented control over the light’s propagation within the material.

To demonstrate the practical applications of this new design methodology, the research team constructed two optical devices commonly used in integrated optics: a compact S-bend waveguide and a power splitter. The S-bend waveguide exhibited an impressive signal loss of less than 1.83 decibels, indicating its efficiency in transmitting light with minimal attenuation. Furthermore, the power splitter effectively divided the incoming light into two equal paths while achieving low excess loss and minimal imbalance, showcasing its ability to maintain signal integrity.

One of the most striking outcomes of this research was the successful transmission of a high-speed data stream at 140 gigabits per second. This transmission utilized a widely accepted telecommunications modulation format, affirming the compatibility of the developed techniques with existing optical communication infrastructures. Such high data rates suggest that these engineered photonic devices could be instrumental in advancing the capabilities of future communication networks.

The research further elucidates how these devices operate through detailed simulations, demonstrating their efficacy in controlling the propagation of light. The simulations include propagation profiles for various configurations such as the straight waveguide, S-bend, and the power splitter, with corresponding transmission spectra and eye diagrams for the signals. These analyses provide a comprehensive understanding of light manipulation at the nanoscale, paving the way for innovative applications in optical technologies.

The implications of this research extend beyond practical telecommunications solutions. By using pseudomagnetic fields in photonic systems, physicists have gained a powerful tool for investigating phenomena typically associated with quantum systems. This newfound capability could facilitate the development of devices for optical computing, enhance quantum information processing, and propel advanced communication technologies into new realms.

Moreover, this research opens new avenues for scientists to explore the behavior of neutral particles under conditions that simulate the effects of magnetic fields. Such explorations could reveal insights into the fundamental principles governing light-matter interactions and lead to novel configurations for enhanced photonic devices. The crossover between condensed-matter physics and photonics could yield surprises as physicists leverage these artificial gauge fields to create unconventional materials and devices.

This imaginative approach to optical control marks a substantial departure from conventional strategies and may redefine how researchers think about light manipulation. By integrating magnetic analogs into the realm of optical science, the research not only reinforces the interdisciplinary nature of contemporary physics but also highlights the potential for future innovations that merge diverse concepts.

The continued exploration of such synthetic fields in the emerging field of optical engineering signifies a promising direction for the evolution of photonic applications. As the demand for faster data transfer rates and improved communication technologies grows, advancements like these will be critical in addressing the challenges posed by modern information systems.

In conclusion, this innovative work exemplifies the strides being made at the intersection of physics and engineering. It enriches our understanding of light and its behavior in engineered systems while providing a robust platform for future research endeavors. As researchers build upon these findings, we can anticipate a wave of exciting developments that will transform the landscape of photonics and telecommunications.

Subject of Research: Pseudomagnetic fields in silicon photonic crystals
Article Title: Arbitrary control of the flow of light using pseudomagnetic fields in photonic crystals at telecommunication wavelengths
News Publication Date: 1-Sep-2025
Web References: Advanced Photonics
References: P. Hu et al., “Arbitrary control of the flow of light using pseudomagnetic fields in photonic crystals at telecommunication wavelengths,” Adv. Photon. 6(6) 066001 (2025), doi: 10.1117/1.AP.7.6.066001.
Image Credits: Image courtesy of Yikai Su (Shanghai Jiao Tong University).

Keywords

Magnetic fields, Photonic crystals, Photonics, Quantum information, Optical devices, Photons

Traditional cameras, particularly those sensitive to mid-infrared wavelengths, face significant hurdles. Mid-infrared light, which lies just beyond visible red light in the electromagnetic spectrum, carries crucial information such as thermal emissions and molecular “fingerprints.” However, cameras designed for these wavelengths frequently demand complex materials, cooling mechanisms, or suffer from noise and limited functionality. The conventional lens systems typically used to focus such light are plagued by restricted depth of field and often introduce optical aberrations and distortions, complicating image analysis.

The research team, led by Professor Heping Zeng from East China Normal University, took inspiration from a predominantly historical imaging method – pinhole imaging – dating back to the 4th century BC and originally documented by Chinese philosopher Mozi. In contrast to lenses which bend light to focus images, a pinhole camera allows light to pass through a minute aperture and projects an inverted image onto a photosensitive surface. This method inherently eliminates lens-induced distortions and possesses an infinite depth of field but suffers from very low light throughput, limiting its use in modern applications.

By marrying this classical concept with nonlinear optics, Zeng and colleagues created an “optical pinhole” inside a nonlinear crystal using intense, highly synchronized laser pulses. This novel approach shifts the role of the traditional mechanical aperture to an ultrafast, light-induced aperture within the crystal itself. Crucially, this nonlinear optical process converts the incoming mid-infrared image into visible wavelengths through upconversion, enabling detection with conventional, highly sensitive silicon camera sensors, which are cost-effective and widely available.

One of the technical breakthroughs enabling this advancement lies in the specially engineered nonlinear crystal with a chirped-period structure. This configuration accepts a wide angle of incident light rays, thereby dramatically expanding the effective field of view without compromising image sharpness. The upconversion approach serves a dual role: it not only translates the otherwise challenging-to-detect infrared photons into visible light but also naturally reduces noise, allowing the system to function efficiently even under extremely low light conditions.

The combination of these effects resulted in images with an extraordinary depth of field exceeding 35 centimeters, alongside a wide field of view greater than six centimeters. Through meticulous experimentation, the researchers identified an optimal optical pinhole radius of approximately 0.20 millimeters that produces consistently well-defined image details across varying object distances. They captured mid-infrared images at a wavelength of 3.07 micrometers, demonstrating sharp image fidelity at distances ranging from 11 to 35 centimeters.

Beyond two-dimensional imaging, the system also showcased remarkable capabilities in three-dimensional image acquisition without reliance on lenses. Using ultrafast synchronized laser pulses as an optical gating mechanism, the team successfully reconstructed the 3D shape of a ceramic rabbit with micron-level axial resolution. This accomplishment underscores the system’s sensitivity and temporal precision, capable of generating depth maps even when the number of photons per pulse was reduced to about 1.5, simulating extremely low-light conditions where traditional detectors typically fail.

Additionally, the researchers demonstrated a simplified two-snapshot depth imaging technique by capturing images of a “stacked ECNU” target at two slightly different object distances, which allowed accurate reconstruction of object sizes and depths. This method did not require the complex timing electronics or pulsed illumination traditionally necessary for depth sensing, pointing toward practical and scalable implementations of 3D imaging.

While the current prototype uses a sophisticated and somewhat bulky laser setup, the team anticipates that advances in nonlinear materials, laser technologies, and integrated photonics will enable the miniaturization and simplification of this imaging platform. Future work is focused on boosting conversion efficiencies, introducing dynamic control to adaptively reshape the optical pinhole depending on the scene, and broadening the operational range of the system to encompass wider mid-infrared spectra. Such developments could birth portable, energy-efficient, and economical infrared cameras with broad usability in scientific and industrial environments.

The reimagining of pinhole imaging with nonlinear optics marks a significant stride toward overcoming the limitations of current mid-infrared imaging technologies. By dispensing with traditional lenses and employing silicon detectors, this methodology opens the door for wider commercialization and deployment of infrared cameras. Expanding further, the principle can be applied to other challenging spectral bands such as far-infrared and terahertz wavelengths, regions notoriously difficult for lens manufacturing and optical design.

This technology not only holds promise for enhancing night-time safety through improved thermal and low-light vision but can also revolutionize industrial inspection processes by providing distortion-free imaging over variable object distances. Environmental monitoring could similarly benefit from cost-effective, sensitive detection of heat signatures and molecular absorption features critical to assessing pollutants and ecological changes.

In essence, this work presents a compelling synergy between optical physics, material science, and laser technology. The team’s integration of an ancient optical concept with nonlinear photon conversion techniques crafts a versatile imaging platform, capable of high sensitivity, wide field coverage, deep focus, and three-dimensional depth sensing, all without the mechanical complexities and aberrations associated with lenses. By translating invisible infrared images into readily detected visible light, these innovations carve a promising path forward in optical imaging science.

As the research progresses, the envisioned compact and adaptive mid-infrared nonlinear pinhole cameras could become ubiquitous tools in fields as diverse as security, manufacturing, biotechnology, and astrophysics. The convergence of affordability, portability, and enhanced image fidelity heralds a new era of multidimensional sensing, offering unprecedented insight into previously elusive light-based phenomena.

Subject of Research: Mid-infrared nonlinear lensless imaging using optical pinhole and nonlinear upconversion techniques.

Article Title: Mid-infrared nonlinear pinhole imaging

Web References:
https://opg.optica.org/optica/abstract.cfm?doi=10.1364/OPTICA.566042

References: Y. Li, K. Huang, J. Fang, Z. Wei, H. Zeng, “Mid-infrared nonlinear pinhole imaging,” Optica, vol. 12, pp. 1478-1485, 2025. DOI: 10.1364/OPTICA.566042

Image Credits: Kun Huang, East China Normal University

Keywords

Cameras; Imaging; High resolution imaging; Optics

The world of quantum mechanics is often perplexing, governed by principles that defy classical logic. At the heart of quantum information science lies the concept of entanglement, which has profound implications for the transmission of information. The challenge often resides in the complexity and inefficiency of traditional methods, which involved intricate optical setups and mechanisms that are susceptible to loss and interference. Such complexities limited advancements in the development of scalable quantum networks and devices.

Metasurfaces, which are engineered two-dimensional materials capable of manipulating light at subwavelength scales, have emerged as a promising tool in photonics. Unlike conventional optics that rely on bulky lenses and mirrors, metasurfaces can alter the properties of light—its phase, amplitude, or polarization—via a compact structure. This unique characteristic raises the possibility of simplifying the processes involved in achieving multiphoton entanglement, potentially catalyzing a renaissance in quantum technologies.

The pioneering work conducted by this research team involved a radical reimagining of the conventional approaches to generating entangled photons. Instead of relying on the cumbersome and often lossy nonlinear optical processes or elaborate setups involving beam-splitters and multiple quantum interference sources, the researchers utilized a single gradient metasurface to facilitate entanglement. This innovative approach enables the control of multiple single photons entering the metasurface from various angles, leading to a sophisticated interference pattern that results in the production of entangled photon pairs.

The implications of such a technique are vast. By enhancing the efficiency and reliability of photon entanglement generation, this method could serve as a central building block for future quantum networks. The researchers stated that their protocol allows for the creation of different types of entangled states and, importantly, enables the fusion of several pairs of entangled photons into larger entangled states. This advancement not only increases the amount of quantum information that can be compacted into a smaller physical footprint but also positions the metasurface as an integral component of compact quantum computing devices.

Professor Ying Gu, the leading author of the study, eloquently illustrated the transformative potential of this technology. He likened it to discovering a shortcut through a complex maze, where the traditional convoluted paths of quantum optics can now be navigated with relative ease using a single, elegantly designed element. This paradigm shift in the design of quantum information systems could facilitate the development of ultra-compact quantum devices that are feasible for integration into everyday technology, such as smartphones and laptops.

The quest for smaller, more efficient quantum devices is spurred by the insatiable demand for powerful computational resources and secure communication channels. As the world rapidly embraces the digital era, the intersection of quantum mechanics with information technology reveals a promising frontier. This new method for generating entangled photons could underpin a myriad of applications, from secure quantum communication protocols to innovative quantum algorithms that promise to perform tasks beyond the reach of classical computation.

Furthermore, entangled photons produced through this novel approach could pave the way for robust quantum networks capable of delivering secure information streams over significant distances. The capacity to generate and transmit entangled states to multiple users simultaneously heralds a new era in quantum communications, where security and speed become paramount. In such networks, quantum states can be distributed, shared, and manipulated, providing a foundation for future advancements in cryptography and secure information-sharing.

Ultimately, the findings discussed in this research empower the quest for integrating quantum technologies into practical applications. The versatility of metasurfaces offers the prospect of scalable solutions that can be deployed widely across various industries, ranging from telecommunications to healthcare. As researchers continue to explore the capabilities of these two-dimensional materials, exciting possibilities unfold.

The intricate balance required in quantum systems poses significant challenges, yet the innovative approach of utilizing metasurfaces as a single manipulative device could simplify the complexities associated with quantum entanglement. The journey toward exemplifying practical quantum devices is layered with obstacles, but with breakthroughs such as these, the path becomes increasingly navigable. The combination of technology and theoretical physics is set to yield transformative outcomes in the fabric of information technology.

As we embrace a future intertwined with quantum technologies, the insights from this research resonate deeply. With every advancement, we edge closer to harnessing the fundamental principles of nature for technological innovation. The synthesis of conventional optical approaches with modern nanotechnology reflects a significant evolution in our understanding and application of quantum phenomena. Researchers and engineers alike will undoubtedly continue to strive for breakthroughs that will redefine our technological landscape in the years to come.

In summary, the work showcased in Advanced Photonics Nexus signifies a major advancement in the quest for efficient multiphoton entanglement. The research team’s commitment to mastering light manipulation via a single gradient metasurface could usher in a new chapter for quantum computing and communication, making once-abstract concepts tangible phenomena that reshape how we interact with and utilize quantum mechanics in our daily lives.

Subject of Research:
Article Title: Multiphoton path-polarization entanglement through a single gradient metasurface
News Publication Date: 13-Feb-2025
Web References: https://www.spiedigitallibrary.org/journals/advanced-photonics-nexus/volume-4/issue-02/026002/Multiphoton-path-polarization-entanglement-through-a-single-gradient-metasurface/10.1117/1.APN.4.2.026002.full
References:
Image Credits: Credit: Peking University

Keywords

Quantum entanglement, Quantum information science, Photons, Metasurfaces, Quantum computing, Quantum information processing.