Cancer and a host of other diseases manifest on a molecular level through specific biomarkers, including proteins, nucleic acids such as DNA or RNA, and various other molecular entities. The challenge with these biomarkers lies in their infinitesimal concentrations during the disease’s nascent phase, often evading detection by existing diagnostic tools. Addressing this, the newly developed sensor harnesses a multi-disciplinary approach merging nanotechnology, gene editing, and nonlinear optics to amplify detection capabilities without relying on molecular amplification methods traditionally used in biomarker assays.

At the heart of this sensor is the phenomenon known as second harmonic generation (SHG), a nonlinear optical process wherein incident photons interacting with certain materials are effectively converted into photons of twice the energy — or half the wavelength. The sensor employs molybdenum disulfide (MoS₂), a two-dimensional semiconductor distinguished by its robust SHG response. By leveraging the MoS₂’s properties, the device creates a platform where subtle biochemical interactions translate directly into measurable optical signals, circumventing common issues with background noise that plague many light-based assays.

To precisely modulate the interaction distance essential for enhancing SHG signals, the team implemented DNA tetrahedrons as nanoscopic scaffolds. These tetrahedral structures are meticulously self-assembled from DNA strands, forming rigid, pyramid-like shapes with nanometer precision. Quantum dots, semiconductor nanoparticles renowned for their size-tunable optical characteristics, were tethered to these DNA frameworks. This arrangement enables fine control over the spatial orientation and proximity of quantum dots relative to the MoS₂ surface, thereby dramatically boosting the local electromagnetic field and, consequently, the SHG intensity.

The sensor’s biomarker specificity and detection mechanism owe much to the integration of CRISPR-Cas12a, a precise gene-editing protein programmed to identify target nucleic acid sequences indicative of disease biomarkers. Upon recognizing its target, Cas12a activates collateral cleavage activity, slicing the DNA strands anchoring the quantum dots. This cleavage disrupts the engineered nanostructure, precipitating a measurable decrease in SHG signal. The direct correlation between the presence of the biomarker and SHG signal modulation endows the sensor with remarkable sensitivity and specificity, enabling detection without the need for traditional amplification methods such as PCR.

This amplification-free detection is a profound leap forward, as conventional biomarker assays often entail time-consuming and costly amplification cycles to elevate the signal beyond detectable thresholds. By contrast, the current technology’s design — combining optical nonlinearity for noise suppression, nanometer-scale engineering for signal enhancement, and molecular precision via CRISPR — fosters rapid and accurate biomarker quantification directly from clinical samples. Such efficiency is poised to redefine the landscape of molecular diagnostics.

In practical application, the team focused on miR-21, a microRNA implicated as a lung cancer biomarker. Initial tests in buffer solutions established baseline sensitivity, followed by validation within human serum extracted from lung cancer patients. The sensor demonstrated exceptional performance, effectively distinguishing the target microRNA from a milieu of structurally similar RNA molecules present in serum, underscoring both its specificity and robustness. This real-world applicability suggests a viable path toward clinical translation.

Beyond lung cancer, the sensor’s modular design and programmable DNA constructs imply versatility across a plethora of diseases and biomarkers. The detection scheme could readily adapt to viruses, bacterial pathogens, and other disease-relevant molecules, unlocking potential applications in infectious disease surveillance, environmental monitoring, and neurodegenerative disease diagnostics, such as Alzheimer’s biomarkers. This universality underscores the sensor’s broad impact potential across multiple domains of healthcare and beyond.

Looking forward, the research team has ambitious plans to transform this laboratory-scale technology into a portable, user-friendly device. Miniaturizing the optical setup and integrating it into a compact form factor could enable bedside or point-of-care testing, expanding accessibility to underserved and remote locations lacking sophisticated laboratory infrastructure. Such advancements would democratize early disease detection, empowering timely interventions and personalized patient management.

The union of DNA nanotechnology, quantum dot-enhanced nonlinear optics, and CRISPR-based molecular recognition represents a triumph of interdisciplinary innovation. This synergy facilitates an elegant sensing architecture that balances speed, precision, and minimal complexity—characteristics critical for next-generation diagnostic tools. As the technology matures and moves toward commercialization, its capacity to reshape cancer diagnostics and monitoring stands to significantly impact patient outcomes and healthcare economics.

Published in the journal Optica, under the title “Sub-Attomolar-Level Biosensing of Cancer Biomarkers Using SHG Modulation in DNA Programmable Quantum Dots/MoS₂ Disordered Metasurfaces,” this research marks a seminal contribution to the field of biomedical optics. The detailed mechanisms and experimental validations outlined exemplify how fundamental physics and molecular biology can converge to create disruptive technologies in medicine.

In summary, the development of this highly sensitive SHG-based biosensor integrates the nanoprecision of DNA assembly, the optical enhancement of quantum dots, and the molecular specificity of CRISPR-Cas12a. This marriage of techniques enables the amplification-free detection of cancer biomarkers at previously unattainable sensitivity levels, bringing the prospect of rapid, accurate, and non-invasive cancer detection closer to reality. As such, it holds tremendous promise for revolutionizing how clinicians detect and monitor diseases, ultimately facilitating earlier interventions and improving survival outcomes worldwide.

Subject of Research: Cancer biomarker detection using light-based sensing technologies.

Article Title: Sub-Attomolar-Level Biosensing of Cancer Biomarkers Using SHG Modulation in DNA Programmable Quantum Dots/MoS₂ Disordered Metasurfaces

Web References:

• DOI Link
• Optica Journal Homepage

References:
B. Du, X. Tian, S. Han, Y. Liu, Z. Chen, Y. Liu, L. Li, Z. Xie, L. Gao, K. Jiang, Q. Jiang, S. Chen, H. Zhang, “Sub-Attomolar-Level Biosensing of Cancer Biomarkers Using SHG Modulation in DNA Programmable Quantum Dots/MoS₂ Disordered Metasurfaces” Optica, 13 (2025).

Image Credits: Han Zhang, Shenzhen University

Keywords: Cancer research, Quantum dots, Metasurfaces, Clinical medicine

At the core of this breakthrough is the concept of soliton pulses—self-reinforcing solitary waves that maintain their shape while traveling at constant velocity. Traditionally, soliton pulses have been pivotal in applications ranging from fiber-optic communications to nonlinear optics. However, compressing these pulses down to the ultra-short regime of just two optical cycles, especially on integrated nanophotonic platforms, has remained a formidable challenge until now. The research team’s novel use of a two-color pumping scheme exploitably tailored the nonlinear dynamics within a nanophotonic waveguide, enabling this dramatic pulse shortening with remarkable stability.

The innovative method hinges on the careful engineering of dispersion and nonlinearity in the nanophotonic waveguide. By introducing two distinct color components, or wavelengths, the team induced a complex interplay between the disparate light fields, facilitating soliton dynamics that are otherwise not accessible with single-color inputs. This two-color excitation enables the generation of ultrashort pulses by harnessing both cross-phase modulation and four-wave mixing effects, mechanisms central to nonlinear optics but rarely exploited in tandem on such minuscule photonic chips.

A key aspect of the methodology involved selecting an ideal material platform and waveguide geometry to maximize nonlinear interactions while managing dispersion with exquisite precision. The waveguide was meticulously designed to feature anomalous dispersion at the primary wavelengths, a prerequisite for stable soliton formation and compression. By finely tuning the relative intensities and phases of the two input colors, the researchers could effectively manipulate the soliton evolution, culminating in the generation of pulses lasting a mere two optical cycles.

The resultant pulses possess peak intensities and temporal resolutions previously unattainable on chip-scale devices, opening new horizons for ultrafast spectroscopy and coherent control protocols. Two-cycle pulse durations correspond to only a few femtoseconds (one femtosecond is 10^-15 seconds), indicating an extraordinary capacity to probe and manipulate phenomena at atomic and molecular timescales. This technological leap offers an integrated alternative to traditional bulky laser systems, potentially democratizing access to extreme ultrafast pulses for a broader range of scientific disciplines.

More strikingly, the robustness of the two-color soliton compression on nanoscale waveguides heralds a paradigm shift in optical pulse engineering. The entire compression process occurs within a compact footprint, aligned with the demands of modern photonic integration. This compatibility with existing silicon photonics and potentially other semiconductor platforms could accelerate the translation of ultrafast optics from laboratory curiosities to practical components embedded in chips for data centers, telecommunications, and high-speed computing.

The research’s meticulous experimental validation combined ultrafast laser sources, nanofabricated waveguides, and precise measurement techniques to characterize output pulse duration and spectral properties. Advanced autocorrelation and frequency-resolved optical gating (FROG) measurements confirmed the compressed pulses’ temporal and spectral fidelity. The consistency between theoretical predictions and experimental results underscores the robustness of the underlying physics and the precision of the fabrication process.

Furthermore, the study delved into the intricate nonlinear optical phenomena governing the soliton dynamics in the presence of two-color excitation. Analytical and numerical simulations revealed a delicate balance between dispersion, self-phase modulation, cross-phase modulation, and higher-order nonlinear effects. The combination leads to the formation of stable two-color solitons that undergo significant temporal compression without fragmentation, a notable advance over previous single-color schemes prone to pulse breakup.

One cannot overstate the potential applications of two-optical-cycle pulses in next-generation technology. For instance, in quantum information science, the ability to produce such precise and ultrashort pulses on a chip could facilitate faster and more coherent quantum gate operations. In biomedical imaging, these pulses could enhance the resolution and contrast of advanced microscopy techniques, enabling real-time observation of dynamic biological processes at the molecular level.

Moreover, telecommunications stand to benefit immensely. The compression of pulses to such an extreme degree can dramatically increase data transmission rates by packing more information into narrower time windows, reducing temporal jitter, and enhancing signal-to-noise ratios. Chip-scale implementation also champions lower power consumption and reduced system complexity, attributes critical for scalable and sustainable telecommunication infrastructures.

The successful nanophotonic two-color soliton compression also provides a versatile platform for exploring fundamental nonlinear optical phenomena with unrivaled resolution. Researchers can now probe ultrafast dynamics in nonlinear media under controlled conditions, fostering deeper insights into soliton interactions, supercontinuum generation, and light-matter coupling at the nanoscale. Such fundamental research may uncover novel physical effects and inspire future photonic technologies.

Looking ahead, the research team envisions extending their work by exploring alternative material systems and extending the spectral range of operation. Materials with stronger nonlinearities or broader transparency windows could push the frontiers of pulse duration even shorter or enable coverage across previously inaccessible wavelength bands. Additionally, integration with other photonic components, such as modulators and detectors, could pave the way for fully integrated ultrafast optical circuits.

The societal impact of this advance is profound, offering a blueprint for accessible ultrafast pulse generation that is both scalable and integrable. By condensing complex nonlinear optical phenomena into chip-compatible formats, the door opens for widespread deployment across industries—from improved metrology and environmental sensing to enhanced health diagnostics and high-precision manufacturing.

In sum, this landmark achievement confirms the tremendous promise of combining nanophotonic engineering with innovative nonlinear dynamics to create ultra-short, high-intensity optical pulses. The demonstration of stable two-optical-cycle pulses through two-color soliton compression is not just a technical feat; it signals a new era in photonics where the manipulation of light on the fastest timescales is both practical and pervasive. As this technology matures, it will undoubtedly underpin numerous scientific discoveries and technological innovations.

The work by Gray, Sekine, Shen, and their collaborators exemplifies the interdisciplinary synergy required to overcome longstanding challenges in ultrafast optics. Their success highlights the pivotal role of nanofabrication, nonlinear optics theory, and precise experimental control in achieving breakthroughs that once seemed out of reach. It will be fascinating to watch how the field evolves as others build upon this foundation, harnessing the power of two-color nanophotonic soliton compression to unlock new dimensions in light-matter interaction.

Indeed, the future illuminated by these ultra-short pulses is bright—literally and figuratively. As integrated photonics continues its rapid ascent, the ability to tailor light’s temporal characteristics with nanometer-scale precision offers tantalizing possibilities. Whether in advancing fundamental science or enabling transformative technology, two-optical-cycle pulses on chip-scale platforms represent a quantum leap forward, securing their place at the forefront of 21st-century photonics research.

Article Title:
Two-optical-cycle pulses from nanophotonic two-color soliton compression

Article References:
Gray, R.M., Sekine, R., Shen, M. et al. Two-optical-cycle pulses from nanophotonic two-color soliton compression. Light Sci Appl 15, 107 (2026). https://doi.org/10.1038/s41377-026-02187-8

Image Credits:
AI Generated

Phonon-polaritons, hybrid quasiparticles arising from the strong coupling between photons and optical phonons in polar crystals, have garnered immense scientific interest due to their ability to confine electromagnetic energy at subwavelength scales within the THz frequency domain. This spectral region is notoriously challenging to harness because it sits between the traditionally accessible electronic and photonic frequencies. The current research addresses this challenge head-on by engineering an interaction between phonon-polaritons and electromagnetic modes that enters the ultrastrong coupling regime—where the interaction strength rivals or surpasses the energies of the uncoupled systems—facilitating new physical phenomena otherwise unobservable in weak or moderate coupling scenarios.

Central to the reported study is the concept of bound states in the continuum, exotic wave modes that remain confined and non-radiative despite existing in the energy spectrum continuum where free propagation is permitted. By integrating BICs into a carefully designed photonic platform, the authors achieve a remarkable level of control over phonon-polariton properties. This innovative coupling scheme generates an unprecedented degree of tunability in the polaritonic dispersion and enhances the coherence and lifetime of the hybrid states.

The experimental framework combines advanced nanofabrication techniques with sophisticated spectroscopic measurements, enabling the precise observation of ultrastrong coupling phenomenology. The research team engineered metasurfaces patterned on polar dielectric substrates exhibiting Reststrahlen bands, where intrinsic phonon-polariton resonances are naturally supported. By tailoring metasurface geometries to support BIC modes overlapping spectrally and spatially with the phonon-polaritons, an efficient hybridization channel is established. This approach manipulates the near-field coupling landscape, offering a new degree of control over light-matter interactions in the THz regime.

One of the most striking outcomes of the study is the emergence of distinctly modified dispersion curves for the coupled modes, characterized by anticrossing behavior and large Rabi splittings, quintessential signatures of ultrastrong coupling. These observations confirm that the system departs fundamentally from linear response theory and enters a nonlinear domain where conventional perturbative methods fail. Such non-perturbative effects open avenues to explore novel quantum optical phenomena within solid-state platforms.

Another critical advantage arising from the BIC-enhanced coupling is the dramatic suppression of radiative losses. Bound states, by definition, decouple from the far-field continuum, rendering the polariton lifetimes significantly longer and the resonances sharper. This quality factor enhancement is essential for applications where coherence and low dissipation are paramount, such as quantum information processing, THz sensing, and nonlinear harmonic generation. The study thus not only pushes theoretical boundaries but also fosters practical innovation in device engineering.

Furthermore, the research elucidates the tunable nature of the hybrid modes. By varying parameters such as metasurface lattice constants, dielectric environment, and excitation angles, the team demonstrated control over the coupling strength and spectral positions of the phonon-polariton resonances. This flexible platform provides an experimental knob to dynamically program optical responses in the THz range, enabling bespoke photonic component designs that can be reconfigured on demand.

Beyond fundamental physics insights, the implications of this work resonate strongly with emerging quantum technologies. Ultrastrong coupling between light and matter is a cornerstone for realizing robust qubits and gates in quantum circuits, as it facilitates rapid coherent exchanges and entanglement protocols. Simultaneously, the enhanced field localization in phonon-polariton systems is conducive to sensing molecular vibrations and detecting minute environmental changes with exceptional sensitivity, paving the way for next-generation THz spectroscopy tools.

Remarkably, the authors documented the emergence of non-trivial topological features within the coupled mode spectrum, hinting at potential links to topological photonics. The interplay between BICs and phonon-polaritons forms a fertile ground for exploring protected edge states immune to backscattering, which can revolutionize waveguiding and robust signal transmission in integrated photonic circuits.

From a materials standpoint, the experiment leveraged well-established polar dielectric materials, such as silicon carbide and hexagonal boron nitride, known for their robust Reststrahlen bands and optical phonon modes. The compatibility of these substrates with existing semiconductor fabrication processes ensures that the new coupling paradigm can be seamlessly integrated into photonic chips, accelerating the translation from laboratory proof-of-concept to real-world applications.

Looking ahead, the findings open multiple research directions. One intriguing prospect is harnessing the ultrastrong coupling regime mediated by BICs for quantum simulators that can emulate complex many-body interactions and phase transitions in condensed matter physics. Moreover, nonlinearity inherent in the ultrastrong regime could be exploited for ultrafast optical switches, modulating THz signals with unprecedented speed and efficiency.

The theoretical framework developed in this study merges classical electrodynamics with quantum optics, deploying a hybrid modeling approach that accounts for the non-perturbative coupling Hamiltonian and electromagnetic boundary conditions governing BICs. Such rigorous modeling not only supports the experimental observations but also serves as a predictive tool for designing future metasurface architectures optimized for specific functionalities.

In conclusion, the manipulation of terahertz phonon-polaritons in the ultrastrong coupling regime via bound states in the continuum stands as a masterpiece of modern photonics research. It transcends traditional engineering limits, unveiling uncharted physical effects with promising practical applications. As the terahertz gap steadily narrows through innovations of this caliber, we anticipate a surge in transformative technologies spanning communication, sensing, and quantum information science.

As the scientific community digests these results, it is clear that the ultra-strong coupling of phonon-polaritons facilitated by BICs is not just a niche discovery but a cornerstone that will redefine how we harness light and vibrations in solid-state platforms. This work exemplifies how careful structuring at the nanoscale enables control over phenomena at the quantum level, charting a course toward unprecedented manipulation of electromagnetic waves in practically relevant regimes.

The implications for future devices are profound. With this approach, engineering platforms that operate beyond conventional limits of speed, size, and efficiency is within reach. From ultra-sensitive biochemical sensors to compact, integrated quantum optical systems, the terahertz domain is poised for a renaissance driven by the principles illuminated in this spectacular study. The fusion of advanced photonics, materials science, and quantum physics witnessed here marks an exciting milestone in the journey toward mastering light-matter interactions.

Subject of Research: Manipulation of terahertz phonon-polaritons in the ultrastrong coupling regime using bound states in the continuum

Article Title: Manipulating terahertz phonon-polariton in the ultrastrong coupling regime with bound states in the continuum

Article References:
Yang, J., Zhang, L., Wang, K. et al. Manipulating terahertz phonon-polariton in the ultrastrong coupling regime with bound states in the continuum. Light Sci Appl 14, 360 (2025). https://doi.org/10.1038/s41377-025-02044-0

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41377-025-02044-0

Local resonances, the fundamental operating principle behind many conventional metasurfaces, enable a certain degree of control over light but are notoriously limited in their angular and spectral ranges. When light interacts with these isolated nano-structures, resonance modes typically suffer from radiation losses, reducing the overall quality factor (Q-factor) and limiting device performance. Moreover, this local approach struggles to maintain uniform optical responses when light is incident from varying directions, creating significant challenges in applications demanding wide-angle functionality. These limitations notably restrict the broad deployment of metasurface technologies in advanced fields such as nonlinear optics, quantum information processing, and ultrasensitive photonic sensing.

In recent years, a paradigm shift has emerged around the development of nonlocal metasurfaces—systems where inter-element interactions give rise to collective optical phenomena rather than isolated responses from single meta-atoms. This nonlocality introduces new degrees of freedom in tailoring light-matter interactions, enabling stronger optical confinement and higher Q-factors across broader angular domains. Central to this innovative approach is the concept of photonic flatbands, exotic dispersion-engineered states where resonances remain nearly invariant over the entire momentum space. This flatband behavior translates to uniform light trapping and enhanced interaction strength over a wide range of incident angles, drastically improving device robustness and efficiency.

A further dimension of interest lies in the engineering of chiral optical responses within metasurfaces. Chirality, the optical property that distinguishes left- and right-handed circularly polarized light, underpins numerous applications ranging from enantioselective sensing to advanced quantum photonics. Designing metasurfaces that simultaneously manifest high-Q flatband resonances and strong chiral selectivity has been a formidable challenge in photonics, primarily because these demands often necessitate conflicting structural symmetries and coupling conditions. Bridging this gap would create multifunctional platforms capable of operating with unparalleled efficiency and specificity in light manipulation.

Addressing these challenges head-on, a recent breakthrough from interdisciplinary teams at Shandong Normal University and the Australian National University advances the state-of-the-art by synergizing the principles of coupled-resonator optical waveguides (CROWs) with anisotropic metasurface architectures. This innovative framework draws inspiration from CROW physics, a concept traditionally applied in photonic waveguides characterized by arrays of weakly coupled resonators that facilitate slow light propagation and high-Q modes. By translating the CROW principles from 1D waveguide arrays into planar, metasurface configurations, the researchers enable photonic flatbands that extend over the complete k-space, ensuring consistent resonant behavior across all incidence angles.

Fundamental to this architecture is the deliberate breaking of in-plane symmetry within the metasurface lattice, achieved through controlled anisotropy and asymmetric coupling between closely spaced optical waveguides. This breaks the degeneracy of photonic states and selectively tailors their polarization response, allowing the realization of flatbands that respond differently to linearly polarized and circularly polarized light. The strategic tuning of lateral coupling slows the effective group velocity of light to near zero, thereby increasing photon lifetime and interaction strength within the metasurface. The resulting ultrahigh-Q factors surpass those accessible with conventional designs, dramatically enhancing device sensitivity and performance.

Experimental verification and rigorous numerical simulations corroborate the existence of both unidirectional and bidirectional flatbands exhibiting selective polarization responses. More remarkably, the team demonstrates the coexistence of chiral flatbands—modes that interact exclusively with a chosen handedness of circular polarization—within a single metasurface platform, a feat not previously accomplished. This chiral selectivity alongside high-Q flatband physics brings about a new class of multifunctional metasurfaces that can spatially and polarization-wise control light with unprecedented precision.

The implications of integrating CROW-inspired physics into metasurfaces are profound. By establishing a versatile design approach that combines slow-light effects, anisotropic coupling, and symmetry engineering, this work unveils a roadmap toward compact optical devices with enhanced light-matter interaction capabilities. Such devices are anticipated to impact quantum optics by enabling stronger, angle-insensitive coupling to quantum emitters, elevate enabling technologies in optical sensing with improved resolution and specificity, and facilitate advanced telecommunication schemes leveraging polarization multiplexing.

Beyond pure scientific interest, the practical applications of these metasurfaces span several cutting-edge technological domains. For instance, in nonlinear optics, the enhanced field confinement and uniform resonant response enable more efficient frequency conversion and harmonic generation processes. In quantum photonics, the precise control over polarization states and resonance lifetimes could bolster photon-based quantum computing components, while chiral flatband platforms pave the way for novel enantioselective sensors with medical and environmental relevance. Furthermore, the integration of such metasurfaces into flat-optics devices promises ultrathin, planar optical systems that replace bulky lenses and filters in consumer and industrial products.

At the heart of this breakthrough lies the elegant fusion of waveguide physics principles traditionally confined to fiber and integrated optics with nanoscale metasurface engineering. This cross-pollination of disciplines showcases how fundamental photonic concepts can be elegantly reimagined to overcome longstanding device limitations, pushing the frontier of light manipulation toward new horizons.

Ultimately, the work led by K. Sun and colleagues not only addresses key inefficiency challenges in metasurface design but also expands the fundamental understanding of how collective resonances and symmetry control can be harnessed for multifunctional optical devices. Their findings offer a vital toolkit for scientists and engineers seeking to develop the next generation of photonic technologies that combine angular robustness, polarization control, and ultra-high resonance quality in a monolithic platform.

As research continues, it is anticipated that further innovations building on this foundation will emerge, possibly exploring dynamic tunability of flatband and chiral metasurfaces, integration with active materials, and exploration of topological photonics within similar frameworks. Such advances promise to deepen our control over the fundamental nature of light, leading to revolutionary capabilities across sensing, communication, and computational photonics in the decades to come.

Subject of Research: Integration of coupled-resonator optical waveguide physics into metasurfaces to achieve high-Q photonic flatbands and chiral optical responses over wide angles.

Article Title: Flatband high-Q metasurfaces inspired by coupled-resonator optical waveguides

News Publication Date: 3-Oct-2025

Web References:
https://www.spiedigitallibrary.org/journals/advanced-photonics/volume-7/issue-05/056008/Flatband-high-Q-metasurfaces-inspired-by-coupled-resonator-optical-waveguides/10.1117/1.AP.7.5.056008.full

References:
Sun, K., et al. “Flatband high-Q metasurfaces inspired by coupled-resonator optical waveguides,” Advanced Photonics, vol. 7, no. 5, 056008, 2025. DOI: 10.1117/1.AP.7.5.056008.

Image Credits: K. Sun (Shandong Normal University)

Keywords

Optical waveguides, Metasurfaces, Optical metamaterials, Chirality, Quantum optics