Wavelength tunability in an all-fiber passively mode-locked laser is studied in both the anomalousand normal-dispersion regimes, by employing a fiber-type birefringence filter. An all-fiber birefringence filter composed of a polarization-maintaining fiber, an inline polarizer, and a polarization controller is implemented, exhibiting continuous wavelength tunability across the fiber-optic telecommunication band around 1560 nm, by adjusting the incident polarization state. The integration of a fiber-type filter into an all-fiber mode-locked laser enables a compact, wavelength-tunable pulsed laser that operates stably in both the anomalous- and normal-dispersion regimes of the laser cavity. The mode-locked laser exhibits maximum tuning ranges of 21.9 nm and 29.9 nm in the anomalous- and normal-dispersion regimes, with pulse durations of 810 fs and 15.7 ps, respectively.
To address the issue of projection-data truncation in photon-counting computed tomography (CT), arising from a sample exceeding the effective field of view of the detector, a dual-domain collaborative truncation-artifact correction network based on the Swin transformer is proposed. First, an edge-extrapolation module is designed in the projection domain, which employs a multiscale feature-fusion approach to extrapolate the edge information of truncated sinograms. Second, a reconstruction algorithm is utilized to simultaneously process both the truncated projection data and the extrapolated projection data, thereby achieving dual-channel information fusion. Finally, an artifact-correction module is constructed in the image domain to capture the transition from detailed features to global structural features within the dual-channel information, thus realizing the correction of truncation artifacts. Experimental results demonstrate that the proposed network can effectively extrapolate truncated data, suppress the interference of truncation artifacts on reconstructed images, and render the corrected images more consistent with real data. Compared to the state-of-the-art dual-Swin method, the results obtained by the proposed method exhibit a 6.4% improvement in peak signal-to-noise ratio (PSNR) and a 6.3% improvement in structural similarity index measure (SSIM).
We investigate how structural disorder governs ultrafast photoinduced transport in thin-film silicon, by comparing polycrystalline silicon (poly-Si) and hydrogenated amorphous silicon (a-Si:H) using optical pump-terahertz (THz) probe spectroscopy. The pump-induced THz transmittance is converted to the complex photoconductivity spectra, which are analyzed with the Drude-Smith model to quantify carrier backscattering and localization. Time-domain transients reveal distinct relaxation kinetics: Poly-Si is described by a single dominant relaxation (tau = 26.34 ps), whereas a-Si:H requires a biexponential response with a faster relaxation time (tau 1 = 1.452 ps) and a slower component (tau 2 = 38.087 ps). In the frequency domain, both materials exhibit non-Drude-like shapes with suppressed low-frequency conductivity, but the degree and evolution of the Drude-Smith backscattering parameter differ, consistent with grain-boundary-limited transport in poly-Si and defect-driven localization in a-Si:H. These results demonstrate that time-resolved THz conductivity affords a quantitative, contact-free analysis to compare disorder-controlled carrier dynamics in technologically relevant silicon phases.
Instant photography has regained attention due to its physical tangibility and analog aesthetics; However, it is still limited to two-dimensional imaging. This study presents the structural design and experimental verification of a three-dimensional (3D) instant photography system based on integral photography (IP). IP records both spatial and angular light-ray information using a micro lens array (MLA), enabling glasses-free 3D image reconstruction. Although instant photographic film provides high angular sampling density owing to its submicrometer-scale photosensitive grains, conventional IP-based systems suffer from alignment errors between the MLA and film, as well as inherent depth inversion caused by ray-geometry inversion between recording and observation stages. To address these limitations, an integrated MLA-film structure is proposed to maintain fixed geometric alignment, and a dihedral corner reflector array (DCRA) is introduced to compensate for depth inversion and achieve orthoscopic reconstruction. The structure was designed to ensure compatibility with roller-based chemical development processes. To isolate optical performance from mechanical and chemical variables, a UV-sensitive photosensitive medium was employed. The experimental results demonstrated stable motion parallax, reduced image distortion, and successful orthoscopic 3D reconstruction, confirming the feasibility of instant photography as a physical 3D recording medium.
This research presents an approach to the design, simulation, and fabrication of a controllable offaxis diffractive optical element. The primary objective is to enhance nonlinear optical systems by offering a cost-effective and versatile solution capable of operating across a range of wavelengths. Utilizing an integrated structural technique, the diffractive optical element is meticulously designed and simulated through Fourier-optics methods. Fabrication is executed using a writing laser lithography system, ensuring precision and reliability. An experimental setup is established to rigorously assess the optical performance of the fabricated diffractive optical element. The primary advantages of this off-axis diffractive optical element are compactness, durability, and an economical manufacturing process, particularly for larger dimensions. Furthermore, its versatility allows application at various wavelengths, including xrays, gamma rays, and ultraviolet light, making it an invaluable component for advanced nonlinear optical systems.
High-speed imaging is a key technology for rapid inspection of large-area samples that improves throughput in industrial applications. As the measurement speed increases, shorter exposure times reduce the collected photon budget; Thus, strong illumination power is required for adequate signal-tonoise ratio. In this study, we propose a high-speed dark-field (DF) microscopy system that preserves the high optical power of laser illumination while effectively suppressing speckle noise. The system combines a ring-shaped fiber bundle with a time delay integration (TDI) line scan camera, thereby reducing effective coherence and improving image contrast during high-speed image acquisition. Ray optic simulation was performed to design the optimal DF illumination system. The experimental results and analysis show the effectiveness of proposed system in high-speed imaging. Compared to the radiant flux limitations of conventional LED-based systems, the proposed imaging system enhances defect visibility in a DF image. We believe that these results highlight the significant potential of the proposed approach for semiconductor metrology and inspection.
A stable dual-loss-modulated Q-switched laser at 1342.1 nm was achieved using both an electrooptic modulator (EOM) and a SnSe2/MoSe2 heterostructure saturable absorber (SA). The output characteristics of the dual-loss modulated laser were investigated. Relative to the active EO Q-switched laser, the pulse width was compressed by 82% and the peak power increased by 2.96 times. Experimental findings showed that the SnSe2/MoSe2 heterostructure SA exhibits great potential for all-solid-state Qswitched lasers, and combined employment of an EO switch and a heterostructure saturable absorber enables significant compression of Q-switched pulse duration and improvement of laser output characteristics.
Autostereoscopic 3D displays are used in augmented reality and virtual reality applications so that users can experience a 3D world without glasses by controlling the direction of light rays at each pixel. However, the use of 3D optics results in a reduction in image quality compared to 2D displays. It is therefore crucial to ascertain the 3D resolution for the accurate presentation of 3D content and to develop high-quality 3D displays using limited resources. This paper presents a methodology for estimating 3D resolution with the use of simulated viewpoint images. First, we introduce a method for generating viewpoint images of a 3D display. We then present a method for measuring three-dimensional resolution from the generated viewpoint images. Experimental results demonstrate that the resolution of the simulated viewpoint images is comparable to the resolution measured in an actual display.
Environmental drift in laser current, contact pressure, and ambient temperature destabilizes multi-mode fiber speckle-based intrusion sensing. To counteract this instability, this paper presents a transfer-learning scheme that performs immediate, periodic micro-updates on-device to a lightweight trainable head while keeping a frozen, ImageNet-pretrained MobileNetV3 backbone. By few-shot updating on a small set of samples reflecting environmental changes gathered on the device, the system tracks slow drift and preserves high detection sensitivity while reducing false alarms. On a Raspberry Pi 5 (RPi5; CPU-only), the head-only update completes in similar to 63 s at worst, enabling minute-scale adaptation that matches the slow drift expected in practice without requiring GPU or cloud retraining.
We propose a complex-amplitude-based inverse-design methodology for broadband and polarization-independent meta-atom and metalens design. By optimizing the complex amplitude of cross-polarized transmitted light via a gradient-based optimizer, anisotropic unit cells that exhibit consistent phase responses at red, green, and blue wavelengths, regardless of polarization, are designed. A set of 12 meta-atoms, covering the full 2 pi phase range in 30 degrees steps, is developed and validated through beam-steering metasurface and metalens simulations. The designed metalenses demonstrate stable focusing performance, with focal-length deviations below 5% under arbitrary polarization states. Our results confirm that the proposed method effectively enables RGB-unified, polarization-insensitive metasurface devices, offering a scalable framework for multiwavelength, multifunctional photonic applications.
Broadband optical systems hold significant value in fields such as target acquisition and detection, yet their design faces challenges including difficulties in obtaining initial structural configurations. Conventional approaches rely on the empirical selection of initial structures, resulting in protracted design cycles and limited generalization capability. This paper proposes a deep neural network-based design methodology for broadband optical systems using PSO algorithms to construct a dataset of initial structures and designing a deep neural network model to predict optimal initial configurations.
The acousto-optic tunable filter (AOTF) is widely used in hyperspectral imaging due to its highspeed tuning over a broad spectral range. However, diffraction sidelobes arising from phase mismatch caused by incident light divergence may lead to image blurring and artifacts along the diffraction direction. To suppress diffraction sidelobes, a method of wavelength-adaptive deconvolution estimation (WADE) was demonstrated, which enables sidelobe minimization across all wavelength channels. We investigated the intensity distribution of the sidelobes on detector pixels, and derived the computational formula of the deconvolution kernel for sidelobe suppression. By using the experimentally measured relationship between sidelobe spatial positions and ultrasonic frequency, combined with the sidelobe intensity determined by the AOTF's diffraction efficiency, wavelength-adaptive deconvolution kernels were estimated. The application of spectrally adaptive deconvolution kernels to hyperspectral image cubes is able to suppress sidelobe-induced blurring across all spectral channels. Experimental results showed that the diffraction sidelobes were effectively suppressed, and image clarity and signal-to-noise ratio were significantly improved by the WADE method.
We propose a phase-modulation method with a simple combination of commercial-level dual in-plane-switching (IPS)-mode liquid-crystal (LC) panels. IPS-mode liquid crystals enable phase modulation using their half-wave retardation changes related to molecular rotation. Therefore, the phase retardation is performed by electric field while preserving the polarization ellipticity of the incident polarization state. While this level of phase modulation is adequate for intensity modulation in conventional LC panels, it falls short for the phase modulation required to realize holographic displays. Our proposed system stacks IPS-mode LC panels and compensates polarization state to increase the phase-modulation range in proportion to the rotation angle of the liquid crystal, while preserving the output polarization. We evaluate the phase-modulation performance of the proposed configuration through interferometry, optically reconstructed holograms to confirm conjugate noise reduction, and multidepth implementation capabilities, thereby validating the potential of a cost-effective commercial IPS-mode LC panel.
Micro-LEDs fabricated from III-nitride materials have attracted significant interest for applications in high-resolution AR/VR/XR and holographic displays owing to their excellent thermal stability, high efficiency, and scalable pixel sizes. However, as device dimensions decrease, optical crosstalk between adjacent pixels becomes a critical challenge that degrades display performance. In this work, we investigate the optical crosstalk behavior of various micro-LED array configurations, including designs incorporating SiO2 parabolic domes and parabolic reflectors. We further examined the effect of mesa dimensions on optical crosstalk.
Circular dichroism (CD) is an important optical property of chiral media that arises from the asymmetric absorption of left-and right-circularly polarized light. CD spectroscopy has a broad range of applications, particularly in the characterization of biomolecules and nanostructures. In this work, we investigate quantum-enhanced CD sensing schemes based on a single double-seeded bright two-mode squeezed state (DSbTMSS), which are experimentally accessible in high-photon-number regimes. Using the Fisher information formalism, we analyze and compare the sensitivity bounds of schemes employing Fock states, two-mode squeezed vacuum states, and bright two-mode squeezed states (bTMSSs). We show that the DSbTMSS configuration provides improved sensitivity compared to the classical limit and schemes based on a pair of bTMSSs in the weak-CD regime.
The miniaturization of optical systems has accelerated the development of planar optical components. In particular, spaceplate technology, which compresses the free space between optical elements, offers a promising route to novel flat optics. However, existing inverse-design approaches for space-plates often require long computation times, rely on continuous optimization, or fail to guarantee sufficient transmission efficiency, limiting their practical usability. In this study, we propose a simple and efficient framework that integrates a genetic algorithm with the transfer-matrix method and angular spectrum method. Optimization is performed under a consistent angular design condition (approximately +/- 10 degrees) to ensure stable convergence. To improve convergence, we introduce an optimization filter and a compact yet effective figure of merit. The algorithm successfully optimizes multilayer spaceplates with high performance within an average of 15 minutes on standard computing hardware. To assess its statistical robustness, we analyzed convergence probability, quality, and time as functions of the Gaussian beam's Rayleigh range, and extended the same evaluation to spherical waves formed by a lens. The results demonstrate that the proposed framework enables rapid and reliable inverse design of multilayer spaceplates, offers a practical tool for efficient design, and contributes to the realization of ultra-thin optical systems.
Spectral scanning delivers ultrafast line rates but sacrifices angular resolution and point density across the field of view (FoV), which degrades the fidelity of three-dimensional (3D) reconstruction. To mitigate this fundamental trade-off between scan speed and spatial resolution, we propose and experimentally validate a frequency-modulated continuous-wave light detection and ranging system that combines mechanical and spectral beam steering. The fast axis implements wavelength-dependent angular deflection using an eight-channel wavelength-division multiplexer and a one-dimensional fiber array. In contrast, the slow axis employs a Galvano scanner to realize a wide FoV. A vertical-cavity surface-emitting laser with a sweep bandwidth of 13.1 nm operating at 10 kHz was used as the swept source. Each interferogram underwent k-linearization, followed by fast Fourier transformation to recover the range. The measured coherence length was approximately 40 cm, and distance-to-frequency mapping in a single channel was highly linear. The hybrid scan produced 896 samples along the mechanically steered axis (FoV: 56.7 degrees) and eight samples along the spectrally steered axis (FoV: 5.98 degrees), with angular resolutions of similar to 0.0633 degrees and similar to 0.854 degrees, respectively. Experiments with multiple targets confirmed accurate 3D reconstruction, and the architecture expanded the FoV and point density while preserving the per-channel sweep bandwidth and range resolution.
In this paper, we propose an innovative method for creating a holographic screen that eliminates the vignetting effect. The proposed approach uses holographic stereogram printing techniques to fabricate a printed holographic screen. In this method, the hologram plane is subdivided into extremely small hogel units, each measuring less than 250 mu m & times; 250 mu m. By capturing a wide angular intensity distribution at each hogel through an interference process between the reference beam and an object beam (generated using a diffuser and objective lens), the recording process is replicated identically across all hogels on the hologram plane. The resulting printed holographic screen demonstrates remarkable uniformity in diffraction efficiency and luminance distribution. During experimental testing, the screen achieved a standard deviation of diffraction efficiency of 0.56, an impressive 11-times improvement over analog holographic screens. Moreover, the average diffraction efficiency reached 34.79%, closely matching analog screen performance, while luminance uniformity soared to 94.24%, representing more than a fourtimes improvement. These results indicate that the proposed printed holographic screen successfully eliminates the vignetting effect and exhibits consistent diffraction efficiency and luminance distribution that meet standard display requirements. Consequently, this innovative technology shows significant potential for future transparent display applications.
In this paper, we present a high-resolution laser scanning system integrating fine machining of objective-only method with high-speed beam steering of a galvanometric scanner. A relay lens configuration transfers scanner angular deflection to the pupil plane of a high-magnification objective without angular loss, maintaining diffraction-limited focusing during rapid scanning. Unlike objective-only approaches limited by throughput and scanner-based systems sacrificing resolution, the proposed system preserves diffraction-limited performance with direct pupil-plane deflection transfer. Using this system, periodic micro-gratings were inscribed inside transparent materials with substantially improved processing speed. Grating periods remained uniform, and fabrication time for identical length structures decreased from minutes to tens of seconds. The system was further applied to Distributed Fiber Bragg Grating fabrication, enabling stable inscription of low-reflection FBG arrays with identical and random Bragg wavelengths. Spatial reflection responses were clearly resolved using radio-frequency modulation interferometry, confirming suitability for distributed sensing. The system enables high-speed, high-precision laser patterning without mechanical rotation assemblies or trepanning mechanisms. As a non-contact approach, it eliminates tool wear, reduces environmental impact from consumables and chemical etchants, and demonstrates strong potential for optical sensor fabrication and next-generation micro-manufacturing.
We present a free-space augmented-reality (AR) near-infrared (NIR) fluorescence imaging system that enables real-time, naked-eye visualization of indocyanine green (ICG) fluorescence during minimally invasive cancer surgery. Unlike conventional systems that require external monitors or wearable optics, our approach projects processed fluorescence images directly onto the surgical site. The system integrates an LED-based NIR excitation module, a NIR-enhanced CMOS camera, an image-processing unit, and a digital-light-projection module. The system's performance is validated using both fluorescence phantoms and the ICR mouse. Accurate coregistration of the projected image with the emission sites is confirmed, achieving a matching accuracy of 98% and a latency of 0.3-0.5 s under phantom-motion test. These results demonstrate the potential of this system to enhance intraoperative guidance and precision during cancer resection.
