Optical Review最新文献

Images captured in low-light environments often suffer from poor visibility and low contrast. Although numerous enhancement techniques have been proposed, most existing methods, while improving brightness and contrast, tend to lose fine details or introduce unnatural artifacts caused by over-enhancement. To address these limitations, this paper proposes a novel image enhancement method that integrates dark region adjustment, image sharpening, and contrast enhancement. The method leverages parametric S-shaped functions: an inverse S-shaped function is first applied to selectively enhance dark regions, followed by multi-scale enhancement with standard S-shaped functions to improve sharpness and contrast while preserving details. In addition, a hue-preserving process is incorporated to maintain natural color appearance. Extensive qualitative and quantitative evaluations demonstrate that the proposed method effectively overcomes the limitations of conventional methods.

In the context of the digital economy era, the demand for computing power is showing an exponential growth trend. Optical computing technology, due to its unique advantages, has become an important development direction for the next-generation computing architecture. To break through the performance bottleneck of traditional computing units, this paper proposes a compact 2-bit optical directional logic multiplier based on micro-ring resonators. The core innovation of this design lies in the use of a micro-ring resonator structure coated with a HfO₂ insulating layer and an ITO activating material, which realizes rapid electro-optic tuning through an applied bias voltage, significantly improving the computing efficiency. The simulation experiment results show that this multiplier structure is highly compact consisting of only 6 micro-ring resonators, with an overall size controlled at 43 μm × 25 μm; it has excellent performance, with an insertion loss as low as 0.34 dB; and it fast operation, capable of stably performing 2-bit multiplication operations. These characteristics fully demonstrate the significant advantages of this design in terms of integration, energy efficiency ratio, and computing speed, providing a feasible technical path for the miniaturization and practical application of optical computing chips.

This paper demonstrates a cost-effective approach for the detection and quantification of fluoride ions using a U-bent plastic optical fiber surface-modified with curcumin-conjugated gold nanoparticles (AuNPs). The U-bent geometry significantly enhances the interaction between the evanescent field and the surrounding medium, thereby increasing the probe’s sensitivity. Curcumin, a natural dye known for its strong binding affinity toward both gold nanoparticles and fluoride ions, acts as a highly selective sensing agent. Upon reacting with fluoride ions, curcumin forms a stable complex that induces a distinct color change and alters the local refractive index (R.I.) of the medium. By illuminating the U-bent probe with a suitable wavelength, this change in R.I. is reflected in the transmitted light intensity, allowing for correlation with fluoride concentration via absorbance measurements. The sensor exhibits a linear response over the range of 0–1 mg/L, with a sensitivity of 0.62 A.U/mg/L and a limit of detection (LOD) of 0.1 mg/L. This chemistry-induced, absorbance-based detection approach eliminates the need for complex and expensive instrumentation, making it well-suited for field deployment. In addition to its high sensitivity and selectivity, the sensor is rapid, eco-friendly, and scalable for commercial applications. Its simplicity in design and seamless integrability with other electronic systems make it as a promising sought after technology.

This study presents the development of a microlens array (MLA) for floating image applications, addressing challenges in both optical design and mold manufacturing. Passive optical floating image systems that operate without external power sources employ various approaches, such as retro-reflectors and dihedral corner reflector arrays. Among these, the MLA offers the distinct advantage of higher image brightness. However, research on floating image devices employing MLA remains limited. This is likely due to constraints on resolution and viewing angle in the MLA method, as well as significant tool wear encountered during mold machining. To overcome these challenges, the authors conducted a study on optical design and mold manufacturing for MLAs. In the optical design phase, a custom macro program in CODE V was used to optimize the MLA geometry for simultaneous improvement of resolution and viewing angle. Floating images formed by the optimized MLA were subsequently simulated using LightTools. The resolution of floating images was evaluated by spot diagrams, and the illuminance of the simulated floating images observed at various angles was also quantitatively assessed. In the mold manufacturing phase, cutting experiments were conducted on a 6.5-inch diagonal electroless Ni-P workpiece using an ultraprecision 5-axis machine tool ROBONANO UiA manufactured by FANUC Corporation. Two types of single-crystal diamond tools—a normal tool and a newly developed wear-resistant tool—were applied. After the experiments, the form error and surface roughness of the molds were evaluated using a laser-probe 3D measurement system (NH-3SP manufactured by Mitaka Kohki Co., Ltd). To summarize the results, the optical design achieved a viewing angle of 45° and an RMS spot diagram radius of 0.41 mm, effectively suppressing ghost rays. In addition, the developed MLA produced a brighter primary image than a conventional MLA, maintaining 78–90% of the front-view illuminance when observed from an angle of 17.5°, and 11–24% even when the observation angle was increased to 22.5°. In the mold cutting experiments, the wear-resistant tool maintained stable form accuracy and surface roughness Ra below 6 nm even after machining 68,000 microlenses. However, the initial form error varied from 0.42 μm to 1.03 μm. A contributing factor to this variation was the mismatch between the nose radius of the tool and the design value of the lens curvature radius.

Design of a novel, alignment-free, ultra-thin multi-layered diffuser film for mini-LED backlight unit and other LED general lighting applications is presented. The ultra-thin diffuser film is inserted between the blue mini-LED array and the QD film for the backlight application. The diffuser film consists of two optical elements, a diffractive layer (DOE or a microprism-array) faced on the mini-LED side and a dielectric multi-layer stack faced on the QD film side. The diffractive layer optimally adjusts the incident angle of the lights emitted out of the mini-LED and the dielectric multi-layer stack acts as an angle-selective filter. The innovative combination of the two optical elements realizes distinct improvement of lighting efficiency and illuminance uniformity without alignment of the diffuser film with the mini-LED array. We also demonstrate the optimal design of the diffuser film using Pareto solution analysis. This method is flexibly applicable to optimally designing not only mini-LED backlight units but also various general lighting applications.

Band-pass multispectral infrared radiometry enables pixel-level retrieval of spectral emissivity and temperature at low cost and over a wide field of view. However, band-integrated measurements strongly couple radiance, temperature, and emissivity within each channel, leading to an underdetermined and highly non-convex inversion problem. In this work, we formulate the problem as a derivative-free, bounded multi-peak optimization constrained by Planck’s law and radiometric calibration. An adaptive escaping grey wolf optimizer (AEGWO) is proposed by incorporating chaotic initialization and stagnation-aware escaping to maintain population diversity. The objective function integrates band-pass energy consistency and channel-wise gain or bias compensation to suppress calibration and transmittance uncertainties. Experimental results show that under an equal computational budget, AEGWO achieves lower error, faster and more stable convergence, and higher stability than PSO, IGWO, LGWO, HHO, and SAGA. The proposed method ensures physical interpretability and robustness by enforcing energy consistency and applying channel correction. It is gradient-free, low-complexity, and deployable with few filters over a large field of view, making it suitable for rapid coating evaluation and in-situ monitoring.

We report an electro-optic Q-switched Nd: YAG slab laser operating at 1.3 μm, based on a diode end-pumping configuration. Utilizing an off-axis positive-branch stable–unstable 57 mm long hybrid resonator with a Nd: YAG slab crystal, we achieved Q-switched laser pulses with an energy of 10.82 mJ and duration of 11 ns at a repetition rate of 1 kHz, corresponding to a peak power of 0.98 MW. The system delivered an optical-to-optical efficiency of 8.3% and a slope efficiency of 15.6%. The measured beam quality factors (M ²) were 1.20 and 1.48 along the orthogonal transverse axes. When the pump power surpassed the lasing threshold, simultaneous dual-wavelength emission at 1319 nm and 1338 nm was initiated, while the conventionally dominant 1064 nm line was effectively suppressed in the laser cavity. These results represent the first successful demonstration of a high-energy, short-pulse 1.3 μm slab laser using electro-optic Q-switching, opening new avenues for high-peak-power solid-state laser sources in 1.3 μm wavelength regime.

Multi-Gbps wireless visible light communication is achieved using red, green, and blue laser diodes combined in a novel laser lighting unit to produce white light by additive color mixing with a low-speckle contrast of ≤ 5% and a high luminous efficacy of 150 lm/W.

The photodetection properties and the equivalent circuit of organic photodetectors (OPDs) based on zinc phthalocyanine (ZnPc) and fullerene derivative (C₆₀) solar cells are discussed. The CuI layer is very effective to enhance the responsivity and the bandwidth of the OPDs. The obtained responsivity is 29 mA/W, and the bandwidth is 300 kHz, which is restricted by the modulation bandwidth of the illuminating laser. The complex impedance of the OPD is measured, and two types of equivalent circuit are discussed. The simple equivalent circuit is composed of a series resistance and a parallel circuit of a resistance and a capacitance, and it approximately describes the measured complex impedance. The precise equivalent circuit is composed of a series resistance and two parallel circuits of resistance and capacitance, describing the ZnPc and the C₆₀ separately, and it describes the measured complex impedance very well. The frequency response is simulated by using the equivalent circuits, and the simulated bandwidth is almost the same as the measured bandwidth.

The conventional slow evaporation approach has been successfully used to generate imidazolium L-tartrate crystal doped with potassium chloride (IMLT.KCl). Single crystal X ray diffraction demonstrates that the IMLT.KCl crystallizes in monoclinic system with space group P2₁ and the Powder X-ray diffraction spectrum further confirmed the strong crystalline nature of the title compound. The presence of functional groups, especially N-H, N-O, C-H, C = O etc..., have been confirmed by Fourier transform infrared and Raman analysis. The optical band gap value is estimated as 5.1 eV using Tauc’s plot. Thermal studies revealed that the grown crystal is thermally stable up to 203 ◦C. The microhardness characterization verified the soft nature of the synthesized crystal. The structural imperfection of the grown crystal was examined by etching studies. Energy Dispersive X-ray analysis is used to identify the elemental composition of the material. The second harmonic generation (SHG) of the grown crystal was confirmed by the Kurtz powder technique.