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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: 17 January 2025
, doi: 10.37188/lam.2025.001
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.
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.
Published
, Published online: 10 October 2025
, doi: 10.37188/lam.2025.045
Computer-controlled sub-aperture polishing technology is crucial for achieving 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 issue, 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 study, we leverage the advantages of a time-varying spacing strategy and theoretically analyse 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, while the CSMRF method demonstrates 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 error and specific frequency error, we identify the optimal combination of adaptive spacing and spiral angle using a genetic algorithm. On this basis, the MSF error is evaluated by combining the characteristic dwell time solution algorithm. Using the inertial confinement fusion optical element as an example, we observe a 99.938% reduction in the amplitude of the PSD curve of the mid-frequency ripple error with a spatial period of 1 mm, while 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 idea for full-band cooperative error control.
Published
, Published online: 09 October 2025
, doi: 10.37188/lam.2025.065
The advent of laser-assisted methods for material slicing attracts a particular attention for technologically important materials as silicon carbide (SiC). Using femtosecond lasers, one can locally initiate multiphoton ionization inside SiC, leading to internal material modifications for slicing SiC ingots into individual wafers. However, intense focused light inside SiC suffers from strong nonlinear effects, such as plasma shielding and self-focusing, which limit energy localization and affect the quality of internal modifications. In this research, we employ temporally-shaped ultrafast trains of pulses for semi-insulating SiC crystal modification. These are generated through an engineered stack of birefringent crystals and permitted successfully slicing a SiC wafer. By adjusting laser parameters, we demonstrate improved energy deposition near the laser focal point and find an optimal combination of laser energy (total energy of pulse train: 10μJ) and number of sub-pulses (8 sub-pulses) to achieve thin single-layer modifications and cracks (thickness: 16.5μm). The suppression of pre-focal plasma shielding and improved control for energy deposition inside crystals are confirmed by side-view luminescence microscopy. Ultimately, the benefits from the technique allow a reduction of the modification layer down to 16.5μm, corresponding to an important advancement for low material-loss SiC wafer slicing.
Published
, Published online: 09 October 2025
, doi: 10.37188/lam.2025.034
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.
Published
, Published online: 09 October 2025
, doi: 10.37188/lam.2025.026
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.
Published
, Published online: 30 September 2025
, doi: 10.37188/lam.2025.064
Meta-holograms, the computer-generated holograms assisted with nano-structured metasurfaces, promise efficient recording of light at the nanoscale. Adopting the multiplexing principle further bestows meta-holography with superb capacity for information storage and imaging applications. However, conventional meta-holograms mostly employ a single physical dimension to multiplex the holograms with incomplete light modulation, which imposes critical limitations on holography fidelity. To address this challenge, here we propose and experimentally demonstrate multi-dimensional multiplexing meta-holograms using full-modulation dielectric geometric-phase metasurfaces. Such metasurfaces enable simultaneous, independent, and arbitrary control of the amplitude, phase, and polarization of spatial light based on the geometric-phase principle, with broadband properties. Thanks to the full-modulation principle, the metasurfaces enable the meta-holograms to multiplex multiple holographic images with engineered patterns, polarizations, and directions, depending on the particular input and output conditions. Compared with the holograms acquired with incomplete light modulation, the designed meta-holograms not only inspire an accurate high-capacity information integration with low crosstalk and ideal energy uniformity, but can also facilitate complex multi-dimensional optical information broadcasting, anti-counterfeit, and encryption in compact optoelectronic devices. This work provides a full-modulation metasurface strategy for robust and scalable multi-dimensional multiplexing meta-holography.
Published
, Published online: 26 September 2025
, doi: 10.37188/lam.2025.050
In short-wavelength optics, millimetre spot-sized ion beam figuring (IBF) is an effective method to eliminate form errors with spatial wavelengths ranging from 10 mm to 1 mm. In this case, the full width at half maximum (FWHM) of the tool influence function (TIF) is typically below 2 mm. In IBF, accurate measurement of a small-sized TIF is critical in determining the removal rate and distribution. In existing research, the online measurement of the TIF has been achieved by scanning the beam current density (BCD) distribution with the Faraday cup (FC). However, due to the convolution effect during scanning, this method is not sufficiently accurate for small-sized TIFs, posing considerable limitations to high-precision applications. This paper presents an in-depth analysis of the convolution effect in TIF measurements. The obtained findings are applied to a corrective TIF measurement method and verified by calculation, simulation, and experiment. The results demonstrate that the proposed method can effectively reduce the measurement error. Specifically, for TIFs with FWHMs ranging from 0.5 to 1 mm, the average measurement error of the peak removal rate (PRR) is reduced from 47.4% to 3.1%, and the average error in the FWHM is reduced from 51.7% to 2.6%. The application of this method to a polishing experiment reduces the root-mean-square (RMS) of the aspherical optical mirror from 1.7 nm to 0.4 nm; moreover, the average convergence rate is 76.4%, which is within the target spatial wavelength range of 15 mm to 3.6 mm. Thus, this paper provides practical guidance for millimetre spot-sized IBF, and is promising for application in high-precision optics.
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