Light: Advanced Manufacturing

Spatiotemporal chaos synchronisation in broad-area lasers

Anbang Wang, Wenhui Chen, Yuncai Wang

Experiments on the unidirectional injection of broad-area vertical-cavity surface-emitting lasers demonstrate the synchronisation of fast spatiotemporal chaos and slow polarization-hopping dynamics under conditions of spectral alignment of the dominant transverse modes. These findings pave the way for high-capacity secure communications and massively parallel information processing enabled by spatial division multiplexing.

Application of suspended waveguide to enable ppb-level on-chip photonic gas sensing

William W. Yu

A recent study reported a suspended chalcogenide waveguide platform that enables ppb-level molecular gas sensing on a centimetre-scale photonic chip using near-infrared photothermal spectroscopy. These results highlight the use of suspended waveguides as a promising approach to achieving ultra-sensitive, fully integrated optical gas sensors by jointly engineering light–matter interaction and on-chip thermal management.

Continuous-phase liquid-crystal optics promise a flat revolution

Bing-Xiang Li

The two-photon polymerization direct laser writing technique was demonstrated for the fabrication of continuous-phase Fresnel zone plates within a polymerizable nematic liquid crystal (LC). The dielectric responses of the LC facilitate the creation of switchable, variable focal length and energy-efficient optical components, making them highly suitable for advanced applications in augmented and virtual reality, adaptive optics, and next-generation photonic systems.

Advanced neural network depicts precise structural colours

Haowen Liang, Juntao Li, Xue-Hua Wang

A mixture probability sampling network is proposed to address the challenge of non-unique mappings between colour and nanostructures. This network successfully outputs structural colours with almost 100% precision, depicting wide-gamut nano-paintings.

Multifunctional single-fiber integration enables closed-loop tumour photothermal therapy

Xiaoyan Guo, Lijun Xu, Jingjing Guo

Interventional photothermal therapy in oncology requires accurate tumour targeting, controlled thermal dosing, and timely feedback. Optical fibres offer a compact route for light delivery; however, most fibre-based approaches remain functionally fragmented. A recent study reports a multifunctional single-fibre probe that integrates tumour identification, photothermal therapy, and real-time feedback through wavelength-division strategies, representing an important step toward closed-loop tumour photothermal therapy.

A 1-MHz VCSEL for compact atomic clocks

Zhou Xin, Yukang Chen, Du Xiang

A 2026 study introduced a transformative design for vertical-cavity surface-emitting lasers (VCSELs), achieving a dramatic narrowing of the intrinsic linewidth to approximately 1 MHz without relying on external optical feedback. This performance is enabled by the monolithic integration of a precisely engineered passive cavity that strategically tailors photon lifetime while suppressing mode competition. The resulting architecture delivers an ultra-compact, scalable, and inherently stable coherent light source, representing a significant advance for chip-scale atomic clocks and quantum sensing technologies.

Subpixel-free full-colour reflective displays via sub-1 V redox modulation

Jinsung Mok, Dagam Kim, Dae-Hyeong Kim

A vibrant, full-colour monopixel reflective display has been developed using a conductive polymer integrated within a Gires-Tournois resonator. By embedding the electrochromic medium inside a phase-engineered cavity, the platform enables sub-volt operation while substantially broadening the colour-tuning range within a single pixel. This architecture reconciles colour versatility with energy-efficient operation and scalability towards micrometre-scale reflective microdisplays.

Minimalist optical achromatic meta-imaging with extended field of view

Boping He, Shuming Wang, You Zhou

A minimalist optical system based on a monolithic integrated meta-axicon cluster achieves achromatic imaging over an extended field of view without relying on conventional dispersion engineering. By harnessing the inherent broadband consistency of Bessel beams and combining it with non-blind image restoration, the design circumvents the strict phase-matching constraints that have traditionally limited large-aperture meta-optics. This work establishes a promising paradigm for combining physics-driven optical elements with computational reconstruction, paving the way toward scalable, high-performance meta-imaging systems.

Metasurface generates singlet oxygen on demand

Yunqi Zhang, Chao He

Although singlet oxygen is central to photodynamic therapy and photocatalysis, rapid and spatially precise generation has remained challenging. A quasi-BIC Au–TiO₂ metasurface couples critical optical absorption to interfacial hot-carrier transfer, enabling molar-level local singlet oxygen production within seconds and wavelength-selective, pixel-resolved cytotoxicity without molecular sensitizers.

Single observation for light-field editing

Qiong-Hua Wang

Inferring explicit illumination cues from a single sparse observation fundamentally decouples scene representation from its captured environment. By shifting illumination from a static, baked-in attribute to a parametrically editable representation, the framework establishes a novel paradigm for scalable, photometrically consistent immersive displays under dynamic real-world conditions.

Widely tunable on-chip green light generation

Yu Xia, Chao Xiang

A widely tunable on-chip green light source in a silicon nitride (SiN) microresonator is demonstrated. By inscribing an effective

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grating in the microresonator via all-optical poling (AOP), green light is generated through second-harmonic generation (SHG). Comb-assisted sum-frequency generation (SFG) is also realised using a coherent Kerr comb arising from the intrinsic

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nonlinearity around the pump wavelength. The combination of these two mechanisms provides fine tunability across the green spectrum. Furthermore, the SFG process introduces a new tuning paradigm, enabling the green output wavelength to be switched over a broad range. These results extend the spectral accessibility of integrated photonics and highlight new opportunities for on-chip light sources.

Beyond desalination: solar-thermal interfaces for mineral mining

Ahmed Mortuza Saleque, Murali Gedda, Qiaoqiang Gan

Solar-thermal interfacial evaporation provides an energy-efficient solution for decentralised desalination. However, its practical application with real seawater is hindered by salt accumulation and brine discharge. In a recent study, a laser-nanostructured, superwicking metallic interface that fundamentally decouples evaporation from crystallization was demonstrated. By using directional capillary transport to direct mineral growth away from the photothermal active zone, this platform enables stable, high-flux desalination of raw ocean water while allowing for nearly complete salt harvesting. This work marks a pivotal shift toward zero-liquid-discharge systems, redefining seawater as both a water source and harvestable reservoir for the circular mineral economy.

Gate-tunable fresnel zone plate based on single-walled carbon nanotubes for terahertz applications

The active manipulation of electromagnetic waves through electrical tuning of nanomaterials is a key advantage for modern technology. We employed the tunable optical response of ionic-liquid-gated single-walled carbon nanotube (SWCNT) films to address a major challenge in terahertz (THz) optics – the limited range of materials with suitable optical properties. In this study, we demonstrated a high-performance THz intensity modulator combined with a focusing Fresnel zone plate (FZP) integrated in electro-chemical cell. We introduce a new approach for designing and fabricating the FZP, based on pre-measured dielectric properties of SWCNT films under applied voltage. The superior shielding effectiveness (up to 8 × 10⁸ dB cm² g⁻¹) of SWCNT films enables the creation of an ultrathin terahertz lens. Electrical gating doubled the minimum refractive index, enhancing lens performance. This also enabled in situ tunability of the intensity modulation depth, from +15 to –20%, with an applied voltage of +2 to –2 V. Although the current switching time is 3.6 seconds, our work presents the first demonstration of an electrochemically gated SWCNT FZP, offering distinct advantages in tunability and thin-film design. Operating at 327 GHz, this FZP is a promising solution for novel adaptive THz communication devices.

Tellurite anti-resonant hollow-core fibre: fabrication, mid-infrared femtosecond laser transmission, and application in tissue ablation

The absence of flexible fibres capable of delivering high-intensity mid-infrared ultrafast lasers (particularly at wavelengths exceeding 5 μm) without inducing pulse distortion or material damage constitutes a major limitation for numerous applications, including laser-based minimally invasive surgery, precision materials processing, and gas sensing. Herein, a tellurite glass anti-resonant hollow-core fibre is proposed that exhibits low transmission loss across the 5–10 μm band (~2 dB/m at 5.5–6 μm or 7.5–8 μm), robust bending resilience (minimum radius of 8 cm), and improved beam quality (output M² reduced from 1.5 to 1.25). Notably, it facilitates the distortion-free delivery of ultrafast mid-infrared pulses from an optical parametric amplification system, without causing spectral broadening or material damage, at an input peak power of 16 MW. In a proof-of-concept demonstration, the developed fibre enables wavelength-selective ablation of biological adipose tissue at 5.75 μm, representing, to the best of our knowledge, the first such demonstration using tellurite hollow-core fibre platform. A record-wide operational bandwidth, extending to 10 μm, is achieved by leveraging the extended infrared edge of tellurite glass. This study confirms that tellurite anti-resonant hollow-core fibres can serve as groundbreaking tools in ultrafast mid-infrared photonics, offering significant potential for addressing challenges in invasive laser surgery, gas-phase spectroscopy, and non-linear optical studies.

Online platform for generating realistic digital phantoms of OCT signals and performing multimodal processing towards optical cancer diagnostics

Optical coherence tomography (OCT), a well-established technique for ophthalmic diagnostics, is now expanding into non-ophthalmic applications, such as dermatology, oncology, and dentistry. OCT signals contain numerous microstructure-sensitive features, including attenuation, speckle statistics, and optical phase. To facilitate the development of feature applications for various tasks and their integration into emerging use cases, we developed a no-code multimodal OCT-integrated online platform for scientific research. This paper describes the capabilities of the developed online platform: realistic digital phantoms of OCT datasets for tuning and benchmarking signal processing approaches; advanced processing of OCT scans to extract feature maps. Several variants of multimodal OCT signal processing have been implemented, including optical attenuation, speckle contrast, depolarisation ratio, strain, and elastographic imaging. This is the first OCT multimodal platform designed to support scientific research aimed at developing various custom-tuned applications, such as disease classification, tumour margin isolation, and severity prediction. We demonstrated the application of this platform for downstream cancer diagnostics using real data from human brain tissue, skin, endometrial tissue, and murine tumour models.

Binder jetting additive manufacturing of high-performance silicon carbide optical mirrors via graphite addition method

Wei Li, Congcong Cui, Ge Zhang, Tingting Zhao, Conghui Guo, Gong Wang

Binder jetting (BJ) additive manufacturing demonstrates significant potential in the fabrication of silicon carbide composites (Si/SiC) mirrors with arbitrary structures. However, the insufficient performance of BJ-prepared Si/SiC, primarily due to high residual silicon (Si) content, limits its application. Here, graphite addition method was proposed to reduce the residual Si content through dual mechanisms. Performance enhancement mechanisms were revealed that graphite, as the self-lubricating phase, improves the flowability of raw powders, which facilitates to reduce the content and size of residual Si. Additionally, β-SiC was formed by the reaction of residual Si and carbon during reactive melt infiltration (RMI) process. The results show that the density of Si/SiC was increased by 5.99% and the residual Si content was decreased by 18.18%. Notably, the flexural strength, elastic modulus and thermal conductivity reached 268.37 MPa, 329.93 GPa and 127.01 W/(m·K), respectively. The dimensional deviations throughout the entire process were -0.11% in length, -0.49% in width, and +0.28% in height. Finally, high-performance Si/SiC mirrors with complex structure were fabricated. Furthermore, the shape accuracy and surface roughness of the Si/SiC mirror were 12.05 nm RMS and 0.772 nm RMS. Therefore, this work manifested the feasibility of graphite addition method for the performance enhancement of BJ additive manufacturing optical Si/SiC mirrors.

Ultrafine three-dimensional nanostructuring in YAG via seed-enabled femtosecond-laser near-field enhancement and wet etching

Three-dimensional micro/nanostructures enable precise tuning of optical properties and have attracted broad interest. However, fabricating highly circular three-dimensional nanopores inside bulk materials remains challenging. Here, we overcome this barrier with a femtosecond laser–assisted wet etching strategy based on internal-seeds. Precisely induced seed defects in YAG produce localized near-field enhancement, lowering the modification threshold and, with wet etching, fabricating well-controlled, nearly circular nanopores with diameters down to 25 nm. Finally, we demonstrate programmable arrays and photonic crystal structures assembled from near-circular pores, establishing a practical route to nanoscale, in-volume three-dimensional nanolithography in crystal.

Rapid fabrication of optical elements for sensing applications using a standard SLA printer

María Amparo Hernández-García, Knut Rurack, Jérémy Bell

The demand for compact, high-performance optical components has driven the development of increasingly sophisticated and miniaturized optical elements, often requiring complex and costly fabrication methods. In this work, we propose a cost-effective and accessible methodology for the fabrication of lenses and free-form optics using a commercially available stereolithography (SLA) 3D printer. A systematic characterization of six transparent photopolymer resins was conducted in terms of their spectroscopic, optical, and morphological properties, i.e., surface and dimensional properties. The evaluation encompassed parameters such as transmittance, autofluorescence, refractive index, and surface roughness. A straightforward and robust printing and post-treatment protocol was developed, facilitating the fabrication of optical components with over 80% transmittance, minimal intrinsic fluorescence, and a surface quality that is compatible with demanding optical applications. The fabricated components demonstrated excellent dimensional fidelity to digital designs and high reproducibility. To demonstrate the versatility of this approach, aspherical, miniaturized, and free-form lenses were designed and integrated into three fluorescence sensing systems, including oil (strip based) and chlorine (microfluidic based) detection platforms, as well as a smartphone-based SARSCoV-2 biosensor. The integration of customized 3D-printed optics has been shown to improve signal collection and readout performance, thereby highlighting the potential of this approach for broad application by a wide range of user groups in rapid prototyping and use in miniaturized optical systems. This work represents a significant advancement in the field of additive manufacturing, particularly in relation to the development of functional photonic devices. Furthermore, it opens new prospects for sensor applications in biosensing, microfluidics, imaging, and integrated optics.

Dielectrophoretic-assisted trapped-assembly for fin-LED display

Minji Ko, Yuna Kwon, SeungJe Lee, Heemin Oh, Keyong Nam Lee, Young Rag Do

We propose a high-precision assembly technique for realizing high-resolution nano- to microscale displays using a trapped-assembly approach that integrates a doctor-blade-based ink-delivery system with dielectrophoresis (DEP)-induced assembly. Octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) were coated onto the pixel-defined layer (PDL) to promote ink trapping and confine fin-LEDs within individual pixels during assembly. Key process parameters—including the viscosity and dielectric properties of the ink solvent, speed and number of blade passes, blade-to-substrate gap, and applied DEP voltage and frequency—were systematically optimised, as these parameters affect solvent confinement of the solvent and fin-LED assembly behavior. Under optimised conditions, achieved through precise control of solvent polarity, DEP force and torque, and doctor-blading parameters, all 400 pixels were successfully assembled. Statistical analysis revealed that 90% of the pixels contained 12-20 fin-LEDs, with an average of 16.3 fin-LEDs per pixel and a standard deviation of 3.5. The overlap ratio was limited to 8%, and 92% of the fin-LEDs were accurately assembled, of which 95% established contact with the p-GaN surface. Electroluminescent devices fabricated using the assembled fin-LEDs exhibited bright and uniform emission across the entire pixel array, confirming their excellent assembly quality and high electrical reliability. The DEP-based trapped-assembly method provides a reliable and scalable strategy for the practical integration of nano- to microscale LEDs in next-generation high-resolution display technologies.

Deep-nanohole-clad waveguides with depth-to-diameter ratio up to 50 000 in single crystals via femtosecond laser writing

Bowen Fan, Yuying Wang, Jiacheng Hu, Xuhu Han, Lijing Zhong, Jianrong Qiu

Femtosecond laser writing offers exceptional flexibility and spatial selectivity, enabling the customization of multifunctional integrated devices with nano-scale resolution. This study introduces a novel approach for fabricating nanohole-clad waveguides with ultra-high depth-to-diameter ratios using femtosecond laser writing combined with spherical-aberration-enhanced focal stretching and selective wet etching. This technique not only achieves record depth-to-diameter ratios (>50 000:1) with nanoholes (diameter: 30-500 nm, depth: 1 500 μm) but enables the creation of functional photonic waveguides. The integration of nanoholes into the waveguide structure provides a platform for multi-functional integrated devices, demonstrating significant tunable optical properties. By adjusting pulse energy and axial focal stitching, the diameter of the nanoholes can be tuned from 30 nm to 500 nm with high precision. Further, fluorescent probes embedded within the nanoholes provide a demonstration of optical sensing capabilities, as the waveguide effectively guides light to excite the probes, generating strong detectable signals. The submicron precision achieved through the process ensures high-quality waveguiding with 10.9 dB mode purity, while centimeter-scale periodic arrays exhibit excellent phase uniformity (deviation <3.9%). This work demonstrates the potential of femtosecond laser writing to directly fabricate high-aspect-ratio nanostructures and integrate functional photonic devices on substrates, opening up new possibilities for multi-functional photonics and sensor applications.

Reflective metagrating polarimeter for single-shot full-Stokes mapping: toward digital histopathology

Histopathology, the study and diagnosis of disease through analysis of tissue samples, is an indispensable part of modern medicine, especially for treating diseases like cancer. However, the practice is time consuming and labor intensive, a circumstance that compels increasing efforts to improve the process and develop new approaches. One of the prospective histopathology techniques involves mapping changes in the polarization state of light being scattered by the tissue, but the conventional implementation relies on bulky polarization optics and is relatively slow. Here, we report the design, fabrication and characterization of a dedicated metasurface polarimeter operating at the wavelength of 640 nm that enables fast parallel (simultaneous) measurements of the Stokes parameters and degree of polarization, with the Stokes parameters determined with ±2% accuracy. To validate its use for digital histopathology we assemble a miniaturized device integrated with the metasurface polarimeter and map polarization state changes in a tissue phantom designed to mimic a biopsy with a cancerous inclusion. The results obtained are compared with those obtained by using a commercial polarimeter, indicating a great potential of metasurface polarimeter based devices and suggesting several possibilities for significant improvement of the current device implementation. We believe that, with these improvements in place, the considered metasurface polarimeter based devices will be ready for practical histopathology applications in clinical environments.

Artificial intelligence-generated photonics: mapping optical properties to subwavelength structures directly via a diffusion model

Subwavelength photonic structures and metamaterials provide revolutionary approaches for controlling light. The inverse design methods proposed for fabricable subwavelength structures are vital for the development of new photonic devices. However, most existing inverse design methods cannot realise direct mapping from optical properties to photonic structures; instead, they rely on forward simulation methods to perform iterative optimization. In this study, we exploit the powerful generative abilities of artificial intelligence and propose a practical inverse design method based on latent diffusion models. Our method directly maps the optical properties to structures without requiring forward simulation and iterative optimization. In this case, the given optical properties can serve as ‘prompts’ and guide the constructed model to ‘draw’ the required photonic structures correctly. Simulations and experiments show that our direct-mapping-based inverse design method can generate fabricable subwavelength photonic structures with high fidelity while following the given optical properties, such as the transmission power, phase, and polarisation responses. This may influence the methods used for optical design and significantly accelerate the research and manufacturing of new photonic devices.

Conformal metamaterial inspired contact lenses−designing, 3d printing and characterization for ocular applications

Haider Butt, Mohammed Ayaz Uddin, Muhammed Hisham, Valentyn S. Volkov

3D printed contact lenses have emerged as promising candidates for advanced ocular applications due to their customizable design and functional versatility. In this study, a novel conformal auxetic-inspired metamaterial ocular disc architecture was developed using digital light processing (DLP), a high-resolution vat photopolymerization technique, and fabricated using an in-house hydrogel formulation. The printed disc was systematically evaluated for its mechanical, optical, and physicochemical performance. Mechanical testing confirmed excellent elasticity and durability, with the hydrated hydrogel exhibiting a tensile modulus of ~0.71 MPa, matching the range of commercial soft contact lenses. Laser profilometry revealed a smooth surface topology essential for user comfort, achieving a root mean square roughness (Rq) of 1.78 µm, a nearly 98% reduction compared to conventionally printed hemispherical lenses. Contact angle measurements (64° hydrated) indicated favorable wettability. Optical characterization exhibited high light transmittance, averaging ~83% across the visible spectrum in the hydrated state. Hydration related properties, including swelling kinetics, water content, and gel fraction, confirmed effective water uptake and retention, supporting oxygen permeability. FTIR spectroscopy validated the chemical integrity of the polymer network, while DSC/TGA analysis confirmed thermal stability up to 300  °C. Furthermore, rheological evaluation indicated a stable viscoelastic profile with notable self-healing behavior. Collectively, this study establishes a 3D printed hydrogel-based conformal metamaterial contact lens platform, offering a promising pathway for the development of next-generation smart ocular devices via additive manufacturing.

Multi-prior physics-enhanced neural network for high-fidelity arbitrary-path optical particle manipulation

Phase gradient force-driven particle transport provides a powerful route for steering microparticles along prescribed trajectories. However, conventional designs typically rely on explicit parametric equations to define optical paths, which limits flexibility and often leads to phase-design errors that degrade field uniformity and transport stability. Although physics-enhanced neural networks (PNs) have recently emerged as a promising tool for light-field manipulation, existing approaches are largely built on scalar diffraction models and therefore fail to fully capture the vectorial nature of tightly focused fields. Moreover, relying solely on a single PN prior to solve ill-posed inverse problems often leads to suboptimal solutions and nonuniform phase gradients. Here we introduce MPPN-RW, a multi-prior physics-enhanced neural network built on Richards-Wolf vector diffraction theory. By embedding the physical forward model, phase periodicity, smoothness regularization, and deep image prior into an untrained deep neural network, MPPN-RW jointly optimizes phase holograms for incident-field modulation. Experiments show that the proposed framework generates arbitrarily complex optical trajectories without parametric equations, while improving intensity uniformity and phase uniformity by factors of 8.9 and 6.1, respectively, over conventional methods. These advances markedly improve the flexibility and robustness of optical particle transport and establish a versatile strategy for microscale particle-transport applications.

Curvature-optimised multilevel SERS substrates formed by femtosecond laser shaping based on electrons dynamics control

Surface-enhanced Raman scattering (SERS) is widely used for trace detection and compositional analysis of biochemical samples. Constructing multidimensionally ordered hotspots with high densities and intensities is crucial for achieving superior SERS substrate performance. Here, we propose a multilevel SERS substrate based on curvature and structural optimisation strategies. We fabricated microlenses with various curvatures via modification and etching using a temporally-shaped femtosecond laser. These lenses were decorated with wrinkles and Ag nanoparticles (AgNPs) via sequential pre-strain application and chemical deposition. Experimental and simulation results demonstrated that the coupling of the wide-field electric field induced by the microlens with the localised plasmonic hot spots on the AgNPs and wrinkles enhanced the localised surface electric field. Curvature-optimised microlenses can increase the wide-field electric fields. The fabricated SERS substrates achieved a low minimum detection limit of 10⁻¹¹ M and an enhancement factor of approximately 1.22 × 10⁷. These substrates can be employed to detect thiram fungicide on crops using two different methods (in situ detection and solution-assisted detection), demonstrating potential for operating efficiently under different usage conditions.

Ultracompact Wide-FOV near-infrared camera with a wafer-level manufactured meta-aspheric lens

Overcoming the trade-off between a wide field of view (FOV) and compactness remains a central challenge for integrating near-infrared (NIR) imaging into smartphones and AR glasses. Existing refractive NIR optics cannot simultaneously support ultrawide angles above 100° and ultrathin total track lengths (TTL) below 5 mm, fundamentally limiting their integration into portable devices. Herein, we present a wafer-level-manufactured meta-aspheric lens (MAL) that simultaneously achieves a 101.5° FOV, 3.39 mm TTL, and F/1.64 aperture within a compact volume of 0.02 cm³. Unlike previous hybrid systems that rely on separate refractive and diffractive components, the proposed MAL introduces a fully integrated architecture that provides a compact form factor. This integration also simplifies fabrication by enabling high-throughput production via micrometre-level precision alignment and bonding on a single wafer, which requires only one dicing step and no additional mechanical fixtures. Furthermore, the design process incorporates manufacturability and enables metalens dispersion modelling, ensuring that the experimental performance matches simulation results. We validated the MAL method using both direct and computational imaging experiments. Despite its small form factor, our scalable MAL demonstrated strong NIR imaging performance in eye tracking, blood vessel imaging, and computational pixel super-resolution tasks. This scalable MAL technology establishes a new benchmark for high-performance miniaturised NIR imaging, and opens the door for next-generation smartphones and AR optical systems.

SGARNet: a deep artifact removal approach for lensless multi-core fiber imaging

Zewen Ma, Jinwen Wei, Juergen W Czarske, Jiachen Wu, Liangcai Cao

Multi-core fiber (MCF) imaging is essential for minimally invasive endoscopy in medicine and industrial inspection. However, the bulky distal optics increase the diameter and invasiveness, causing tissue damage. Its applications are further constrained by low spatial resolution and prominent honeycomb artifacts. We present a lensless MCF imaging approach based on Spectral-Guided Artifact Removal Network (SGARNet). In this framework, a physics-informed prior is embedded in a lightweight SpectralGate module to suppress lattice-frequency artifacts in the feature domain. The experimental results show a 12.12 dB improvement in PSNR and 0.4064 increase in SSIM, indicating superior performance over previous methods. The robustness and generalizability are confirmed by successful reconstructions across diverse textural complexities and biological tissue samples. These results demonstrate potential for practical deployment in compact and safer biomedical endoscopes.

Precise motion tracking and velocimetry using chirped power oscillation wave

Precise high-speed motion tracking and velocimetry are critical underlying technologies in various areas such as advanced manufacturing, robotics, and modern physics. Mature detection methods such as Doppler velocimetry and dual-comb interferometry measurements cannot achieve directional unambiguity detection without a trade-off between speed and precision due to the inherent limitations of their system mechanisms. In this study, we propose an innovative high-speed and precise motion detection method based on chirped power oscillation waves (CPOW) generated by dispersion-controlled dual-swept lasers. Our results demonstrate that the displacement and velocity of the target can be directly identified via the power oscillation of the zero-frequency point on the interference signals after carefully controlling for the difference in group delay dispersion between the two beams of the swept lasers. We achieved sub-micrometer-scale displacement measurement accuracy with an update frame rate on the order of MHz and a relative velocity measurement error of better than 0.1%. Furthermore, the proposed method can also be used to reveal the unpredictable operational states of motion-control equipment influenced by mechanical vibrations. This dynamic displacement measurement and velocimetry method based on CPOW opens the door to advanced, fast, and high-precision ranging systems.

Simulation and experimental investigation of homogeneity measurement in side-polished transparent cylindrical materials

Characterizing the optical homogeneity of side-polished cylindrical transparent materials remains challenging. To address this challenge, a four-step absolute measurement method based on a Fizeau interferometer is proposed for cylindrical transparent materials. The refractive index distribution is derived from wavefront data obtained through four sequential measurements: empty-cavity interference, transmission interference, front-surface interference, and back-surface interference. A homogeneity error of 1 × 10⁻⁵ was introduced in MATLAB simulations, yielding a result of 9.9999 × 10⁻⁶ with a residual error of 8.0319 × 10⁻¹¹, confirming the method’s validity. Two repeated measurements performed at different times yielded homogeneity values of hom₁ = 9.5802 × 10⁻⁶ and hom₂ = 9.3331 × 10⁻⁶ (2.7% deviation), demonstrating good robustness. The uncertainties of the two measurements were 1.0997 × 10⁻⁶ and 0.8767 × 10⁻⁶, respectively, and the expanded uncertainties were 2.1994 × 10⁻⁶ and 1.7534 × 10⁻⁶, respectively. This method effectively isolates surface errors from material homogeneity, providing a practical approach for the accurate characterization of cylindrical optical components.

Off-axis bright- and dark-field OCT for non-destructive subsurface defect detection in silicon carbide

The exceptional mechanical and thermal properties of silicon carbide (SiC) make it vital for advanced optics; however, its hardness and brittleness cause subsurface defects (SSDs) during machining that impair performance and longevity. Current detection methods remain destructive and inefficient, whereas conventional optical coherence tomography (OCT) struggles with limited penetration, surface scattering interference, and poor defect contrast in this highly scattering material. We propose a non-destructive off-axis bright- and dark-field synchronous OCT (BADF-OCT) method that captures complementary scattered signals at dual angles to enhance weak subsurface feature detection. The broadband 1100–1500 nm near-infrared spectral-domain OCT system provides high axial resolution with adequate SiC penetration. Experimental validation on reaction-bonded SiC demonstrates clear discrimination between surface fracture and subsurface crack layers, providing reliable detection of micrometre-scale defects at depths up to ~200 μm. Three-dimensional volumetric imaging combined with bright/dark-field data fusion effectively distinguishes true SSDs from surface contaminants, significantly improving the recognition accuracy. This study is expected to contribute to the development of high-energy lasers, large-scale scientific facilities for light sources, and advanced optical manufacturing.

Freeform terahertz structures fabricated by multi-photon lithography and metal coating

Direct-write multi-photon laser lithography (MPL) combines highest resolution on the nanoscale with essentially unlimited 3D design freedom. The groundbreaking potential of this technique has been demonstrated in various application fields, including micromechanics, material sciences, microfluidics, life sciences, as well as photonics, where in-situ printed optical coupling elements offer new perspectives for package-level system integration. However, millimeter-wave (mmW) and terahertz (THz) devices did not yet leverage the unique strengths of MPL, even though the underlying devices and structures could also greatly benefit from 3D freeform microfabrication. A key challenge is that functional mmW and THz structures require materials with high electrical conductivity and low dielectric losses, which are not amenable to structuring by multi-photon polymerization. In this work, we introduce and experimentally demonstrate a novel approach that leverages MPL for fabricating high-performance mmW and THz structures with hitherto unachieved functionalities. Our concept exploits in-situ printed polymer templates that are selectively coated through highly directive metal deposition techniques in combination with precisely aligned 3D-printed shadowing structures. The resulting metal-coated freeform structures (MCFS) offer high surface quality, low dielectric losses, and conductivities comparable to bulk material values, while lending themselves to in-situ fabrication on planar mmW and THz circuits. We experimentally show the viability of our concept by demonstrating functional THz structures such as ultra-broadband chip-chip interconnects, THz probe tips, and suspended THz antennas. We believe that our approach offers disruptive potential in the field of mmW and THz technology and may unlock an entirely new application field for laser-based 3D manufacturing.

Spatiotemporal photothermal modulation microscopy (SPM²) for high-sensitivity deep-subwavelength defect inspection

The weak scattering and overwhelming background of periodic structures fundamentally hinder the inspection of subwavelength defects embedded in dense nanopatterns. Herein, we introduce an actively tunable photothermal modulation scheme that leverages the temperature-dependent resonance shifts of silicon nanostructures to engineer their far-field scattering signatures. Localised optical heating induces a redshift in the underlying resonances, producing a strongly nonlinear change in both the defect and background scattering. This modification amplifies defect-induced perturbations and suppresses background contributions, substantially enhancing the inspection sensitivity for deep-subwavelength defects. A coupled optical-thermal model quantitatively captures the temperature rise and transient thermal evolution and predicts the resonance modulation achievable under the given pump conditions. This study establishes reversible, non-destructive photothermal resonance modulation as a general mechanism for dynamically engineering optical contrast in patterned media, offering a pathway towards high-sensitivity wafer inspection and tunable nanophotonic sensing.

Full-chip EUV curvilinear mask optimization

Pinxuan He, Jiamin Liu, Honggang Gu, Song Zhang, Qi Xia, Hao Jiang, Shiyuan Liu

As semiconductor manufacturing advances towards finer feature sizes, mask optimization (MO) has become increasingly critical in optical lithography to ensure pattern fidelity. In extreme ultraviolet (EUV) lithography, full-chip MO encounters significant challenges in terms of computational accuracy and efficiency, which are exacerbated when employing curvilinear patterns. Herein, we propose a full-chip curvilinear MO framework for EUV lithography that integrates deep-learning-enabled forward modelling with gradient-based inverse optimization. We represent the forward model using a tuneable U-net trained on data generated by an accurate and efficient modified Born series method. This model achieves a significantly lower complexity by describing the 3D mask effect through amplitude and phase perturbations. For inverse optimization, gradients are calculated via the adjoint method using slices of the 3D mask field as input—a significantly more efficient approach than utilising the entire 3D field. Evaluated under typical scenarios, the proposed framework demonstrates a four-order-of-magnitude speedup compared with MO based on the finite-difference time-domain method without compromising accuracy. Leveraging this framework, the MO for a 1 mm² wafer area with 19.41 nm critical dimensions can be completed in 31.7 h using 1,000 GPUs, highlighting its potential for full-chip EUV curvilinear mask optimization.

Multi-task large-scale integrated optical vision processor using ultra-fast parallel nanofabrication

Optical neural networks (ONNs) promise ultra-fast low-power machine vision; however, visible-wavelength implementations are constrained by limited neuron density and accuracy. Although random projections provide efficient untrained feature encoding, we advance ONN performance using a high-throughput randomised multi-focus two-photon lithography (TPL) platform that fabricates millions of 500 nm neurons at the millimetre scale within 15 min. The resulting platform achieves ≥97% classification accuracy in multiple image classification and keypoint detection tasks using minimal digital parameters that outperform other devices of comparable neuron densities while enabling compact integration with camera systems through its transparent design. Our results indicate that ONNs can serve as scalable and practical solutions for high-performance multi-task machine vision.

Various technologies for the testing of asphere and freeform optics and their calibration

Christof Pruss

Metrology is a prerequisite for all advanced fabrication methods. For precision optical systems, optical surfaces require form accuracies down to nanometer level-accross areas with lateral dimensions measuring centimeters to decimeters, or even larger for astronomical instrumentation. This poses a challenge specifically for aspheric and freeform surfaces that scientists have tackled ever since the fabrication technologies allow the production of these, from an optics designer point of view, superior surfaces. In this work, we discuss several state-of-art metrology approaches with a focus on calibration. Specifically, we restrict ourselves to interferometric areal methods that have the potential to acquire a dense 2D surface deviation map within a short data acquisition time of less than a minute.

Review of fringe projection profilometry: from geometric triangulation to computational 3D imaging

With the rapid advances in digital technologies and intelligent manufacturing, three-dimensional (3D) imaging based on fringe projection has laid the foundation for machine vision, industrial metrology, and interdisciplinary applications. This review provides a comprehensive overview of fringe projection profilometry (FPP), which is a widely adopted technology in the 3D imaging landscape. First, we outline the fundamental principles, implementation procedures, and historical developments of FPP. Next, we present the continuous advances in algorithms, hardware, and applications that collectively push FPP towards increasingly challenging measurement scenarios. Subsequently, we provide a dedicated discussion to explain the transformative roles of artificial intelligence (AI) and computational imaging (CI), delineating how their progress is initiating a shift from traditional geometric approaches towards computational 3D imaging. The current challenges and emerging trends in 3D imaging are further identified and discussed. Looking ahead, FPP is expected to evolve into a next-generation 3D imaging technique, achieving unprecedented accuracy, efficiency, and adaptability through the co-optimization of systems with algorithms and the convergence of AI and CI, thereby empowering more complex requirements across industrial, biomedical, and scientific domains.