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Published
, Published online: 06 November 2025
, doi: 10.37188/lam.2025.073
Multispectral imaging is a common method to enhance tissue differentiation based on different cell or tissue structures. These differences arise from the unique structural properties of each tissue type, which result in characteristic differences in spectral absorption. In the context of distinguishing between healthy and malignant tissues, differences are observed not only in spectral absorption but also in their elastic properties. To improve the reliability of measurement devices, we present a novel bimodal measurement system that includes a hyperspectral and an elastographic Fourier transform profilometry system to combine the individual results and to improve the overall task of tissue differentiation. The results of both subsystems show good ability to differentiate between healthy and malignant tissue. However, some limitations were identified for each individual sensor concept, such as contamination with pathological dye in hyperspectral imaging and insufficient sample thickness in elastographic measurements. Nevertheless, the multimodal combination of the individual sensor systems ensures good tissue differentiation. While the elastographic sensor can differentiate tissue even when contaminated with pathological staining agents, hyperspectral imaging can be used on very thin tissue samples and also enables the detection of tumor boundaries.
Published
, Published online: 05 November 2025
, doi: 10.37188/lam.2025.046
Holographic patterns that integrate printings and holograms into a single device have received extensive attention in optical security owing to their attractive aesthetics and concealment. However, the sophisticated structures of metasurface-based optical devices require a time-consuming fabrication process, hindering the practical application of holographic patterns in optical security. In this study, a novel double-layer holographic pattern that employs simple microholes and microvoids as optical modulation units is designed and experimentally demonstrated. The two layers of the structure arrays are synchronously processed in a transparent material through a single serial-stitching of dynamic 3D spatially modulated femtosecond pulses that are proposed for the rapid fabrication of large-area multi-layered patterns. The fabricated holographic pattern appears as a dynamic grayscale image under white light incident at different angles and projects encoded holographic images under laser illumination. By transforming microholes into microcraters by ultrasonic treatment, the reconfiguration of the holographic pattern can be realized based on refractive index modulation using liquid immersion. The proposed reconfigurable holographic patterns with simple structures and visible sizes enable the recoding of multiple pieces of information, making them practical optical security elements with a wide range of applications in anti-counterfeiting and information encryption.
Published
, Published online: 31 October 2025
, doi: 10.37188/lam.2025.072
New technologies that combine standard procedures for tissue sample extraction and analysis with optical spectroscopy and imaging represent a new step in the development of tumour tissue diagnostics. Optical percutaneous needle biopsy is a promising method for increasing the diagnostic efficiency of the procedure by selecting the area for sample extraction and obtaining information about vascular changes and the metabolism of biological tissues at the needle tip. This study provides a comprehensive analysis of existing technical solutions to address various diagnostic tasks: studying the metabolic status of tissues for the adjustment of treatment protocols, differentiating healthy and tumour tissues for navigating puncture needles, and obtaining preliminary diagnoses of the nature of neoplasms. Technical systems for assessing the perfusion and metabolic characteristics of biological tissues using fine-needle probes have been described. Fine-needle probe designs for biopsies of various organs are also presented. The results of using optical percutaneous needle biopsy in liver and breast cancers are demonstrated.
Published
, Published online: 30 October 2025
, doi: 10.37188/lam.2025.044
X-ray scintillation detectors play an irreplaceable role in medical imaging, security inspections, and nondestructive detection. Recently, all-inorganic lead-free metal halide scintillators have attracted attention for addressing the drawbacks of lead-halide perovskites, such as severe self-absorption and toxicity. Nevertheless, high-resolution, flexible, and cost-effective lead-free scintillators are desirable for X-ray imaging applications. In this study, we designed a zero-dimensional hybrid cuprous halide, (MTP)2Cu4I6 (MTP+ represents [C19H18P]+), and synthesized single crystals. (MTP)2Cu4I6 shows intense yellow emission (618 nm) and a large Stokes shift of 185 nm, almost eliminating the effect of self-absorption. As a result, (MTP)2Cu4I6 exhibited a near-unity photoluminescence quantum yield (99.9%) with a light yield of 43800 photons per megaelectron volt. Moreover, (MTP)2Cu4I6 demonstrates an impressive detection performance with a fast response time of 2.18 μs, a good linear response ranging from 0.038 μGyair s−1 to 53.4 μGyair s−1, and a low detection limit of 37.6 nGyair s−1. In a conceptual experiment, large-area flexible (MTP)2Cu4I6/polydimethylsiloxane (PDMS) scintillation films were fabricated to investigate their X-ray imaging performance. The (MTP)2Cu4I6/PDMS film exhibits a high-spatial resolution of 10.2 lp mm−1 when the modulation transfer function is 0.2 and superior flexible detection performance. The short lifetime, high-light yield, low toxicity, and low cost of (MTP)2Cu4I6 facilitate the development of next-generation X-ray scintillators.
Published
, Published online: 29 October 2025
, doi: 10.37188/lam.2025.074
Optical non-destructive inspection technologies are becoming increasingly crucial in semiconductor manufacturing to meet the growing demand for miniaturized, high-density, and integrated semiconductor devices. Conventional inspection techniques typically analyse semiconductor devices from the front side, but this approach poses challenges for highly integrated devices with micro and high-aspect-ratio structures due to scattering issues and low signal-to-noise ratios. Furthermore, it becomes impossible to measure the depth of Cu-filled through-silicon vias (TSVs) due to the low penetration depth of light in metals. Here, by combining chromatic confocal microscopy and spectral interferometry with an IR optical frequency comb centred at 1560 nm, which can penetrate silicon, we demonstrate a new backside silicon inspection technique. The demonstrated method is capable of simultaneously measuring thickness and refractive index with a high spatial resolution of ~14 μm and a repeatability of 72.3 nm for the 534.2 μm silicon wafer. We also conducted the first successful depth measurements of Cu-filled TSVs in commercial memory products using IR spectral interferometry with a high-numerical aperture (NA) lens, for both individual Cu-filled TSVs and TSV arrays under different NA conditions.
Published
, Published online: 27 October 2025
, doi: 10.37188/lam.2025.075
Modern technologies have been heavily reliant on semiconductor chips driving their innovation. These nanoscale-featured devices have created the need for precise lithographic tools that enable the microscopic patterning of such features. With a large drive to keep the cost of lithography tools low while maintaining high resolution, recent works have explored alternate solutions to existing commercial tools. Therefore, this study investigates a low-cost photothermal lithography technique that utilizes a phase-change material to allow for high-resolution 200 nm features to be patterned. The technique we present in this work does not only provide a sidewall roughness of < 10 nm but also uses light-insensitive materials, allowing for delicate features to be patterned under non-restrictive environments. We present the theoretical limits of our laser writing system and demonstrate the experimentally achieved features, describing in detail how we overcome some of the diffraction and thermal limits in order to achieve ultimate resolution and sidewall roughness. This was achieved with near 100% yield as every patterned feature survived all stages of the sample processing with minimal defects.
Published
, Published online: 25 October 2025
, doi: 10.37188/lam.2025.067
Spectral imaging systems are critical for revealing new information about the structure and composition of diverse samples, but traditional approaches that use generic ‘bandpass’ spectral filters are sub-optimal in challenging scenarios with low data signal-to-noise ratio (SNR). To address this, we introduce the concept of hyperpixels: a novel, compact, application-specific spectral filter array approach compatible with integration atop CMOS image sensors. Each element of a hyperpixel filter array is engineered to selectively transmit specific spectral components optimized for the target application, analogous to arrays of multivariate optical elements designed for analyte sensing. Hyperpixels achieve spectral tailoring through precise height engineering of multiple sub-pixel Fabry-Perot resonators covering each pixel area. Building on our earlier work exploring the feasibility of this approach1 , we present the first experimental validation of this concept. First, we develop a design framework based on matched filter theory and demonstrate its effectiveness by creating a set of 4 hyperpixels optimized to discriminate among 4 distinct spectral reflectance targets. Fabricated 2 × 2 arrays of hyperpixels are compared to optimal bandpass filter arrays through both spectral and imaging characterization. Our results demonstrate that hyperpixels outperform optimal bandpass filters in separating spectral components, achieving a 2.4× improvement in unmixing matrix condition number (p = 0.031) based on measured spectra, and a 3.47× reduction (p = 0.020) in condition number during imaging experiments. Importantly, simulations confirm that this advantage is robust even in the presence of significant fabrication errors. These findings demonstrate the superior spectral discrimination capability of hyperpixels over traditional approaches. With straightforward customization, scalable fabrication, and compatibility with CMOS sensors, hyperpixels offer a highly versatile solution for real-time imaging. Potential use cases include micro-endoscopy, capsule endoscopy, industrial inspection, and machine vision, where compact form factors and ability to handle low raw SNR are critical. Future improvements in design and fabrication will further enhance performance, enabling new possibilities for application-specific spectral imaging.
Published
, Published online: 21 October 2025
, doi: 10.37188/lam.2025.063
Additive manufacturing (AM) encompasses a variety of techniques for creating three-dimensional (3D) structures with intricate geometries, including droplet-based and layer-based methods. Among these, vat photopolymerization (VPP), a layer-based AM technology, stands out for its ability to achieve high resolution and relatively low cost. However, traditional VPP techniques face inherent challenges such as the stair-step effect and limited fabrication speed, which constrain their application for seamless, high-throughput manufacturing. To address these limitations, continuous and volumetric photopolymerization approaches have emerged, offering enhanced precision and faster production capabilities. This study introduces a novel linear volumetric printing technique, Light-Initiated Direct Growth (LIDG), which precisely controls light energy distribution in 3D space within a liquid resin. Unlike other methods, LIDG enables curing light to penetrate pre-printed regions, achieving continuous polymerization along the Z-direction. By leveraging controlled light projection, optical energy is manipulated to initiate photopolymerization at targeted voxels, facilitating the rapid and uninterrupted construction of 3D polymer structures. A detailed optical energy distribution model is developed for LIDG, accounting for light absorption and attenuation characteristics within photopolymer resins. Additionally, the effect of resin viscosity on printing quality is systematically analyzed. Demonstrations of LIDG’s capability to fabricate large macro-scale structures with fine micro-scale features underscore its potential for advancing applications, including biomedical devices, optical systems, and soft robotics.
Published
, Published online: 14 October 2025
, doi: 10.37188/lam.2025.068
Determination of position and orientation is essential in advanced manufacturing, automation, and material physics analysis. Traditional high-precision multiple degree-of-freedom (DOF) measurement techniques often rely on multiple probe beams to measure cooperative targets, introducing system complexity and potential measurement errors. Here, we present a novel method for three-degree-of-freedom measurement that employs low-coherence spatial interferometry (LCSI) with a single probe beam. Unlike conventional approaches, this method eliminates the need for cooperative targets and extends applicability to both smooth and rough surfaces. By leveraging the geometric characteristics of the coherence envelope and pulse alignment in a mode-locked femtosecond laser, our system acquires low-coherence interferograms at flexible axial positions, overcoming the constraint of equal-arm interference. Demonstrated at a real-time speed of 100 Hz, the method achieves arcsecond-level angular precision and sub-micrometer distance precision. Furthermore, it enables simultaneous measurement of multiple targets within the field of view, offering transformative potential for applications such as ensuring pose consistency in precision assembly and monitoring deformation during environmental testing. This work presents a novel single-probe-beam measurement approach, providing a compact and versatile solution for multi-DOF dynamic measurement.
Published
, Published online: 12 October 2025
, doi: 10.37188/lam.2025.056
In recent years, metasurfaces on planar substrates have been extensively investigated and methods for their fabrication have been implemented. However, fabricating metasurfaces on highly curved surfaces remains challenging because of the difficulty in achieving precise mechanical positioning on curved geometries using current lithographic techniques. This limits applications that require finer and more accurate structures. This paper introduces a novel lithographic approach for patterning structures on curved surfaces. By leveraging the natural aberration of a convex lens to focus the beams, this approach enables the creation of adjustable ring and split-ring configurations. Ring-shaped patterns with an average structural width of 1.79 µm were exposed, exceeding the resolution of previously reported annular lithography techniques by a factor of 10. Moreover, this approach offers a defocus tolerance that is 10 times greater than that of conventional direct laser writing lithography, thus reducing the influence of positional errors caused by substrate geometry. Consequently, patterns on a photoresist-coated dome were successfully exposed, marking a pioneering achievement. This study paves the way for creating ring-shaped metasurfaces and other structures on highly curved surfaces.
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