In photonic crystal slab (PCS) structures, the bound states in the continuum (BICs) and circularly polarised states (dubbed C-points) are critical topological polarisation singularities in momentum space that have garnered significant attention owing to their novel topological and optical properties. In this study, we engineered a novel PCS imager featuring two C-points with opposite chirality through symmetry breaking, resulting in maximal asymmetric transmission responses characterised by near-unity circular dichroism (CD) values. By harnessing the chiral selectivity of the C-points, a high-CD PCS imager can provide two sets of optical transfer functions (OTFs) to facilitate both edge detection and bright-field imaging. Notably, one set of OTFs was finely tuned to a Lorentzian line shape to achieve perfect edge detection. We developed a multifunctional imaging system by integrating a PCS imager into a traditional optical system. Both theoretical and experimental demonstrations confirmed that this system provides bright-field and edge-enhanced images with micrometer-scale resolution. Furthermore, these two independent functions can be easily switched by altering the circular polarisation state of the light source.
In this study, a ray tracing model based on the law of reflection in vector form was developed to obtain the design parameters of multipass cells (MPC) with dense spot patterns. Four MPCs with distinct patterns were obtained using an established mathematical model. An MPC with a four-concentric-circle pattern exhibited the longest optical path length (OPL) of approximately 38 m and an optimal ratio of optical path length to volume (RLV) of 13.8 cm-2. A light-induced thermoelastic spectroscopy (LITES)-based methane (CH4) sensor was constructed for the first time using the developed optimal MPC and Raman fiber amplifier (RFA). A novel trapezoidal-tip quartz tuning fork (QTF) was used as the detector to further improve the sensing performance. The CH4-LITES sensor exhibited an excellent linear response to optical power and CH4 concentration. The minimum detection limit (MDL) of the CH4-LITES sensor reached 322 ppb when the output optical power of the RFA was 350 mW. The Allan deviation of the system indicated that the MDL decreased to 59.5 ppb when the average time was increased to 100 s.
One of the challenges in the field of multi-photon 3D laser printing lies in further increasing the print speed in terms of voxels/s. Here, we present a setup based on a 7 × 7 focus array (rather than 3 × 3 in our previous work) and using a focus velocity of about 1 m/s (rather than 0.5 m/s in our previous work) at the diffraction limit (40×/NA1.4 microscope objective lens). Combined, this advance leads to a ten times increased print speed of about 108 voxels/s. We demonstrate polymer printing of a chiral metamaterial containing more than 1.7 × 1012 voxels as well as millions of printed microparticles for potential pharmaceutical applications. The critical high-quality micro-optical components of the setup, namely a diffractive optical element generating the 7 × 7 beamlets and a 7 × 7 lens array, are manufactured by using a commercial two-photon grayscale 3D laser printer.
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.
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.
Ultra-high-precision, computer-controlled sub-aperture polishing technology is crucial for achieving full-band, high-precision optical components. However, this convolution material-removal method introduces a significant number of mid-spatial frequency (MSF) errors, which adversely impact the performance of optical systems. To address this problem, we propose a novel controllable spiral magnetorheological finishing (CSMRF) method that disrupts the mechanism of conventional constant tool influence function (TIF) convolution material removal. In this paper, we leverage the advantages of a time-varying spacing strategy and theoretically analyze how time-varying spacing, combined with the spiral swing process of the TIF, mitigates MSF ripple errors. The time-varying spacing method highlights the importance of controlling the characteristic frequency, whereas the CSMRF method has a smoothing effect on the errors within the MSF band. Our findings confirm that time-varying spacing and spiral swinging have complementary effects in managing MSF errors. Furthermore, by constraining the MSF and specific frequency errors, we identify the optimal combination of adaptive spacing and spiral angle using a genetic algorithm. We apply a non-negative gradient constraint dwell-time solution algorithm based on the Lagrange regularization method to deterministically evaluate the specific MSF error. Using the application of an inertial confinement fusion optical element as an example, we observe a 99.938% decrease in the amplitude of the PSD curve of the mid-frequency ripple error with a spatial period of 1 mm, whereas the mid-frequency PSD curve remains within the standard line. Therefore, the proposed method can effectively control the specific MSF error distribution. This variable convolution kernel (TIF) sub-aperture polishing method provides a new concept for full-band cooperative error control.
In the area of computer-aided optical design most software packages rely on a surface list based data structure. For classical on-axis lenses – such as camera lenses - the list-based data structure is a suitable way for managing lens data. However, for modern high-end optical systems such as off-axis free-form designs, multi-path systems or for accurate tolerance analysis of complex opto-mechanical systems, the list-based approach often reaches its limits. In this paper we present a new tree-like data structure that is able to solve many of the problems that emerge from surface list based data structures.
This study proposes a novel heterodyne grating interferometer designed to meet the multi-dimensional atomic-level measurement demands of next-generation lithography systems and large-scale atomic-level manufacturing. By utilizing a dual-frequency laser source, the interferometer enables simultaneous three-degree-of-freedom (3-DOF) displacement measurements. Key innovations include a compact, zero dead-zone optical path architecture, which enhances measurement robustness by minimizing sensitivity to laser source instabilities and atmospheric refractive index fluctuations. In addition, we present a systematic crosstalk error analysis, coupled with a corresponding compensation algorithm, effectively reducing crosstalk-induced errors to below 5%. Experimental evaluation of the 90 × 90 × 40 mm3 prototype demonstrates outstanding performance metrics: sub-nanometer resolutions (0.25 nm for X/Y-axes, 0.3 nm for Z-axis), superior linearity coefficients (6.9 × 10−5, 8.1 × 10−5, 16.2 × 10−5 for X-, Y-, and Z-axes, respectively), high repeatability (0.8 nm@1000 nm for all axes), exceptional long-term stability (20 nm XY-plane drift, 60 nm Z-axis drift over 1000 s), and practical measurement ranges exceeding 10 mm in-plane and 2 mm axially. Comparative analysis with state-of-the-art sensors demonstrates significant advantages in measurement precision, system integration, and multi-axis capability. This advancement highlights excellent potential for applications in integrated circuit fabrication, atomic-scale manufacturing, and ultra-precision metrology for aerospace systems.
Perovskite photovoltaics upholds the most prominent position in the field of tandem technology development. In this aspect, the creation of perovskite material with suitable bandgap (≥ 1.65 eV) is necessary. And in order to achieve the best device characteristics, the high-quality film formation is crucial. To get a high-quality film, the solvent engineering approach stays at the forefront. However, although the solvent engineering was well discussed for such conventional material as MAPbI3, the field of wide bandgap perovskite materials is still lacking in this area. This paper presents the solvent engineering approach to improve the efficiency and stability of the conventional wide bandgap perovskite material Cs0.17FA0.83PbI1.8Br1.2. Here we utilize several solvents such as traditional N,N-dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and acetonitrile. It was demonstrated that implication of any binary DMF-X solvent improves the solar cell efficiency compared to the pure DMF solution, but the ratio of the X solvent is unique for every X and the foundation for the X influence is also unique. The addition of 2.4 M of DMSO is considered the best to improve the stability and efficiency of laboratory devices, however implementation of AcN allowed to produce 25 cm2 mini-modules with the PCE reaching 10%.
Thermal protection and comfort are essential for instruments and humans, especially in high-temperature scenarios such as fires and steelworks. Existing thermal protective windows absorb external radiation and heat when exposed to thermal sources, thereby failing to provide thermal comfort to users. Herein, we present a nanophotonic-engineered thermal protective window (NETPW) strategy that incorporates a visible-light transparent broadband directional thermal emitter and a low-emissivity coating into commercial polycarbonate (PC) windows. In comparison to a PC window exposed to a 700 K thermal source at a half-view angle of 50°, the proposed NETPW exhibits remarkable temperature reduction (~77.7 ℃) by reflecting external radiation and enhancing directional radiative cooling. Simultaneously, the NETPW effectively inhibits heat emissions toward users, resulting in a significant improvement in thermal comfort, with a user’s sensible temperature reduction of 57 ℃. Moreover, the NETPW exhibits high visible transparency, high-temperature resistance, scratch resistance, and impact resistance. The seamless integration with existing windows provides a novel approach for controlling thermal emission and optimizing energy exchange.
Defect inspection is critical in semiconductor manufacturing for product quality improvement at reduced production costs. A whole new manufacturing process is often associated with a new set of defects that can cause serious damage to the manufacturing system. Therefore, classifying existing defects and new defects provides crucial clues to fix the issue in the newly introduced manufacturing process. We present a multi-task hybrid transformer (MT-former) that distinguishes novel defects from the known defects in electron microscope images of semiconductors. MT-former consists of upstream and downstream training stages. In the upstream stage, an encoder of a hybrid transformer is trained by solving both classification and reconstruction tasks for the existing defects. In the downstream stage, the shared encoder is fine-tuned by simultaneously learning the classification as well as a deep support vector domain description (Deep-SVDD) to detect the new defects among the existing ones. With focal loss, we also design a hybrid-transformer using convolutional and an efficient self-attention module. Our model is evaluated on real-world data from SK Hynix and on publicly available data from magnetic tile defects and HAM10000. For SK Hynix data, MT-former achieved higher AUC as compared with a Deep-SVDD model, by 8.19% for anomaly detection and by 9.59% for classifying the existing classes. Furthermore, the best AUC (magnetic tile defect 67.9%, HAM10000 70.73%) on the public dataset achieved with the proposed model implies that MT-former would be a useful model for classifying the new types of defects from the existing ones.
Endoscopes are indispensable for minimally invasive optical applications in medicine and production engineering. The smallest lensless endoscopes often use digital optics to compensate the intrinsic distortions of light propagation of multimode or multicore fibers. However, due to the wavelength dependency of the distortion, the approach is restricted to a narrow spectral range, which prevents multispectral imaging modalities. We employ a spatial light modulator with a high stroke above 2
, to generate a hologram which minimizes overall phase distortion for multiple spectral bands. This enables lensless multicore fiber single-shot RGB endoscopy, for the first time in the world. Many applications in advanced manufacturing and biomedicine such as in vivo tissue classification are enabled.
Quartz tuning forks have been recently employed as infrared photodetectors in tunable laser diode spectroscopy because of their high responsivities and fast response time. As for all sensitive elements employed for photodetection, the main drawback is the limited bandwidth of their absorption spectrum. For quartz crystals, the high absorptance for wavelengths above 5 µm guarantees excellent performance in the mid-infrared range, that cannot be easily extended in the visible/near-infrared range because of its transparency from 0.2 to 5 µm. In this work, we report on the development of a laser surface functionalization process to enhance the optical absorption of quartz crystals, named hereafter Black Quartz, in the 1-5 µm spectral range. Black Quartz consists of surface modification of quartz crystal by ultra-fast-pulsed-laser-processing to create localized matrices-like patterns of craters on top. The surface modification decreases the transmittance of quartz in the 1-5 µm range from > 95% down to < 10%, while the transmittance above 5 µm remains unchanged. The Black Quartz process was applied on two quartz-tuning-forks mounted in a tunable laser diode spectroscopy sensor for detecting two water vapor absorption features, one in the near infrared and the other one in the mid-infrared. A comparable responsivity was estimated in detecting both absorption features, confirming the extension of the operation in the near-infrared range. This works represents an important and promising step towards the realization of quartz-based photodetector with high and flat responsivity in the whole infrared spectral range.
Monolithic multi-freeform optical structures play significant roles in advanced optical systems by simplifying system structures and enhancing optoelectronic performance. However, manufacturing and measurement present significant challenges, which require the simultaneous assurance of form quality and relative positioning of multiple functional surfaces. Consequently, a deterministic form-position deflectometric measuring method is proposed based on Bayesian multisensor fusion, which effectively overcomes the inherent limitation of deflectometry in absolute positioning. Calibration priors were marginalised in the measurement model to improve fidelity, and a fully probabilistic measurement framework was proposed to eliminate numerical bias in conventional sequential optimisation approaches. Finally, a geometric-constraint-based registration method was developed to evaluate the form-position quality of freeform surfaces. The experimental results demonstrated the measurement accuracy could achieve a level of one hundred nanometres for surface forms and a few microns for surface positions.
Femtosecond 3D-printing offers tantalizing avenues for miniaturization and integration of micro optical systems. Available photoresists, however, restrain their utility in liquid immersion, especially in media with refractive indices larger than n = 1.33, such as glues or biomedical fluids. We present monolithic 3D-printed immersion optics, equipped with compact microfluidic sealing to protect the micro optical device from intrusion of liquid immersion media. We experimentally demonstrate diffraction limited performance in water, silicone-, and immersion oil, for a tailored aspherical-spherical doublet with a numerical aperture of NA = 0.625 and a footprint as small as a single mode optical fiber. Such compact monolithic immersion micro optics yield high potential to advance miniaturization for in situ biomedical sensing and robust coupling between fibers and photonic integrated circuits.
This review considers the modern industrial applications of augmented reality headsets. It draws upon a synthesis of information from open sources and press releases of companies, as well as the first-hand experiences of industry representatives. Furthermore, the research incorporates insights from both profile events and in-depth discussions with skilled professionals. A specific focus is placed on the ergonomic characteristics of headsets: image quality, user-friendliness, etc. To provide an objective evaluation of the various headsets, a metric has been proposed which is dependent on the specific application case. This enables a comprehensive comparison of the various devices in terms of their quantitative characteristics, which is of particular importance for the formation of a rapidly developing industry.
Transparent objects are widely used in various fields, leading to increasing demand for methods of measuring them. However, the measurement of such objects has always been challenging owing to the intricate refraction and reflection phenomena they exhibit. Given that traditional contact measurement methods can damage transparent objects, the use of non-destructive measurement techniques, particularly those based on optical principles, is considered preferable. As a result, various non-destructive measurement methods have been developed for transparent objects by leveraging the unique characteristics of light, and a comprehensive review is imperative for exploring these innovative methods and their potential applications. This review accordingly begins by elucidating the necessity of measuring transparent objects and exploring the concept of transparency. Next, an overview of various non-destructive optical measurement techniques spanning macro-, micro-, and general-scale applications is presented, followed by a discussion of their respective advantages and limitations. Finally, the paper concludes by outlining future directions for potential advancements in the field. This review is expected to serve as a valuable resource for newcomers in the field of transparent object measurement and assist researchers seeking to integrate these techniques into interdisciplinary studies.
ISSN 2689-9620 EISSN 2831-4093
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2021, 2(3): 350-369. doi: 10.37188/lam.2021.024
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2023, 4(4): 519-542. doi: 10.37188/lam.2023.031
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2025, 6(1): 5-13. doi: 10.37188/lam.2025.001
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2021, 2(3): 313-332. doi: 10.37188/lam.2021.020
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2021, 2(1): 59-83. doi: 10.37188/lam.2021.005
