Search Results (1,199)

As the exponential growth in advanced compute workloads drives intra-datacenter interconnects to ever increasing bitrates, optical networking equipment has risen to the challenge by shifting from NRZ signaling to bandwidth efficient modulation methods such as PAM4. As these modulation schemes introduce an inherent SNR penalty, maintaining low bit error rates (BER) forces optical links to operate at significantly higher optical powers. However, increasing the optical power leads to photodetectors reaching one of their fundamental bottlenecks caused by the space-charge effect, limiting their ability to provide a high-speed response under high-power illumination. This work presents the design, fabrication, and characterization of a waveguide-integrated photodiode with dual optical inputs (DIPD) designed to overcome this limitation. Specifically, we demonstrate that combining a dual-fed architecture with targeted cross-sectional geometric optimizations effectively distributes the photocurrent density to delay the onset of space-charge saturation. Experimental validation demonstrates a high responsivity of ≈0.91 [A/W] (for O-band wavelengths) and a large electro-optic bandwidth (EOBW) of ≈58 [GHz], all under high-power illumination and CMOS driving voltages. Full article

Yeasts play a vital role in food fermentation processes, where their viability, stress tolerance, and metabolic performance directly influence product quality and process efficiency. Controlling and modulating yeast behavior represents a challenge in the food industry, particularly in non-thermal processing contexts. Ultraviolet (UV) technology has traditionally been applied as a microbial control tool; however, yeast response mechanisms to UV irradiation extend beyond simple inactivation. Depending on wavelength, dose, and treatment conditions, UV exposure can lead to complete inactivation, partial reduction in viability, or induce stable phenotypic changes associated with cellular stress responses and Deoxyribonucleic Acid (DNA) damage processing. This review examines current knowledge on yeast–UV interactions across different food matrices, highlighting how UV treatments influence yeast physiology and functionality. In addition, recent studies suggest that UV-induced genetic alterations, when properly controlled, may contribute to yeast diversification and functional modulation without the use of genetically modified organisms. The review discusses technological opportunities, practical limitations, and future research needs, emphasizing the dual role of UV technology as a tool for yeast control and as a potential driver of functional modulation. Full article

Long-wavelength flank waviness plays a critical role in the excitation behavior of geared transmissions. While coordinate measuring machine (CMM) exports provide detailed geometric information, conventional evaluations typically focus on individual tooth curves and do not quantify circumferential inhomogeneity across teeth. This study introduces a tooth-to-tooth long-wavelength waviness inhomogeneity indicator (ΔW1) derived directly from Klingelnberg-style MKA plot files and demonstrates its behavior on a large industrial dataset comprising 3375 measured gear parts. Each flank curve was detrended using a second-order polynomial fit, and lobe-based waviness amplitudes (W1–W3) were extracted via sine–cosine projection. The proposed ΔW1 metric was defined as the difference between the maximum and minimum W1 values across measured teeth within the same part. To eliminate measurement edge effects, a mid-section evaluation (10–90% of the face width) was additionally performed. Population-level analysis revealed consistent separation between geometrically homogeneous and inhomogeneous parts, with ΔW1 values in the most critical components exceeding 7–9 µm after mid-section filtering. Unsupervised clustering based on ΔW1 and maximum W1 further distinguished a high-variability subset of parts exhibiting systematic long-wavelength modulation patterns. The results demonstrate that circumferential waviness variability can be quantified using standard CMM outputs without additional hardware or specialized measurement procedures. The proposed indicator provides a practical geometric screening tool for large production batches and establishes a reproducible framework for linking detailed flank geometry to manufacturing consistency assessment. Although acoustic validation is outside the scope of the present work, the metric is intended as an NVH-relevant geometric risk indicator for future vibroacoustic correlation studies. Full article

In the current paper, the nonlinear absorption characteristics and laser modulation performance of the ternary anisotropic semiconductor material ZrGeTe₄ were successfully explored. The recovery time of the ZrGeTe₄-PVA thin film was measured to be 5.74 ps by the pump–probe technology. By employing ZrGeTe₄ as a saturable absorber, a passive mode-locked Yb-doped fiber laser was demonstrated for the first time. In the 1 µm mode-locked operation, the central wavelength was 1031.29 nm, the pulse repetition rate was 24.85 MHz, and the pulse width was 786.3 ps. In an Er-doped fiber laser operating at a wavelength of 1561.10 nm, the pulse width was as short as 1.26 ps with a repetition rate of 4.38 MHz. The results show that ZrGeTe₄ has excellent broadband nonlinear optical characteristics. Full article

Artificial intelligence computing systems increasingly demand high-bandwidth, high-extinction-ratio, chip-to-chip optical transceivers. Silicon microring modulators (MRMs) are attractive for such transmitters due to their compact footprint and wavelength-division multiplexing capability. However, for a specified extinction ratio, the optical bandwidth for high-Q MRMs and the driver’s RC time constant prevent conventional single-segment MRM drivers from supporting 100 GBaud class PAM4 transmission. This work presents a broadband driver exploiting the feedforward technique for dual-segment MRMs. It extends electro-optical bandwidth while maintaining a high Q-factor and extinction ratio. The input signal is split into low- and high-frequency components that drive the long and short segments of the MRM, respectively. The long segment uses a broadband low-pass driver, whereas the short segment employs a driver with a programmable bandpass response near the Nyquist frequency. The design space is obtained from an equivalent electro-optical model under constant group-delay constraints. Simulations at 1310 nm show that the 3 dB electro-optical bandwidth improves from ~50 to >70 GHz and that a 200 Gb/s PAM4 optical eye diagram exhibits an open eye; the energy efficiency is 1.44 pJ/bit, and the extinction ratio improves from 2 dB to 4.1 dB. The proposed technique provides a tunable electro-optical co-design approach for high-bandwidth-density, high-extinction-ratio silicon photonic transmitters. Full article

We report the generation of sub-50 fs mid-infrared (MIR) pulses using a fiber-integrated system comprising a several-centimeters-long chalcogenide (As₂S₃) fiber and a fluoride (ZBLAN) fiber. Initially, 127 fs pulses at 2.8 µm are generated via the soliton self-frequency shift in the fluoride fiber. These pulses are then coupled into the As₂S₃ fiber, which provides substantial normal dispersion at this wavelength, enabling temporal stretching to achieve pulse durations of 1.02 ps (8 cm), 2.06 ps (15 cm), and 4.45 ps (24 cm), corresponding to a maximum stretch factor of approximately 35. Simultaneously, the pulses undergo significant spectral broadening via self-phase modulation during this process. Subsequent nonlinear compression within an optimized ZBLAN fiber yields compressed pulses as short as 46 fs, representing a compression ratio of approximately 63%. This work represents, for the first time, picosecond stretching and sub-50 fs nonlinear compression in a fiber-integrated architecture at 2.8 μm, establishing a critical component for future all-fiber MIR-chirped pulse amplification systems. Full article

Accurate and stable measurement of carbon dioxide (CO₂) concentrations in industrial flue gases is critical for emissions monitoring and carbon management. The present study developed a wavelength-modulated tunable diode laser absorption spectroscopy (WMS-TDLAS) system for measuring high-concentration carbon dioxide (CO₂) in flue gases, covering a range of 3–20% (by volume). To mitigate optical intensity fluctuations caused by particle scattering and detector gain drift in harsh flue gas environments, a normalized second harmonic (2f/1f) detection scheme based on a single-harmonic peak was employed. A digital phase-locked amplification algorithm replaces the conventional hardware lock-in amplifier, enabling simultaneous demodulation of multiple harmonic components and enhancing system integration. A comparison of the digital locking method with a commercial lock-in amplifier reveals that the former demonstrates comparable or superior stability, with relative standard deviations of 0.04% for the 2f signal and 0.02% for the first-harmonic signal. In order to address the sensitivity degradation of WMS-TDLAS at elevated CO₂ concentrations, a pressure control strategy was introduced. Maintaining the measurement cell pressure at 70 ± 0.005 kPa resulted in a 2.74-fold enhancement in system sensitivity at 13.01% CO₂ and a more than one-order-of-magnitude increase at 20.01% CO₂ compared to operation at atmospheric pressure. Concentration measurement error under reduced pressure also decreased from 1.101% to 0.075%. The system exhibited 0.6% repeatability in high-concentration CO₂ measurements, signifying its aptitude for industrial flue gas monitoring applications. Full article

Underwater imaging is generally subject to complex degradation issues such as color distortion, contrast degradation, and detail blurring due to the selective absorption and scattering of light wavelengths by water. Existing deep learning methods have limitations in the collaborative optimization of local details and global color. To address this issue, this paper proposes a multi-scale enhancement network based on global and local feature fusion. By integrating the advantages of CNN and Transformer, it achieves joint optimization of global color correction and local detail enhancement. Specifically, MGLFNet extracts global and local features of the image through the global and local feature fusion block in the core component of the multi-scale convolution–Transformer block and performs dynamic fusion. Meanwhile, to extract features at different scales to enhance performance, we design a multi-scale convolution feed-forward network. Through the action of the fusion module and the feed-forward network, a color-rich and detail-clear enhanced image is obtained. A large number of experimental results show that MGLF-Net outperforms comparison methods in both qualitative and quantitative evaluations of visual quality, with PSNR and SSIM values of 25.37 and 0.918 on the UIEB dataset, respectively, as well as low memory usage and computational resource requirements. In addition, detailed ablation experiments prove the effectiveness of the core components of the model. Full article

Wavelength modulation spectroscopy (WMS) is a representative implementation of tunable diode laser absorption spectroscopy (TDLAS), enabling reliable gas component analysis with concentration-related information derived from harmonic component extraction, while offering enhanced noise immunity for trace gas sensing in open environments. However, due to the strong coupling between laser wavelength and intensity, wavelength modulation inevitably introduces residual amplitude modulation (RAM), which significantly degrades measurement accuracy. To address this issue, this study introduces a RAM suppression algorithm based on multiple harmonic component decoupling (MHCD), using the second-harmonic lateral peak inclination angle (LPIA) as a characteristic indicator. Unit harmonic operators for the first, second, and third harmonics are designed, and an original harmonic reconstruction model is established via linear superposition of harmonic components. The optimal harmonic component ratio is determined at the composite operator with the maximum cross-correlation coefficient, and RAM noise is eliminated through a multi-harmonic decoupling matrix. Repetitive measurements on 22 mm pharmaceutical vials with 4% oxygen concentration demonstrate that MHCD reduces the second-harmonic LPIA from 18.07° to 8.56°. Concentration discrimination experiments conducted on seven groups of 22 mm vials with 2% concentration steps (0–12%) show that MHCD increases the true positive rate by 6–11% and decreases the false positive rate by 4–9%, confirming its effectiveness for pharmaceutical online inspection applications. Full article

Insulation deterioration is the leading cause of premature failures in high-voltage (HV) power equipment, with partial discharge (PD) serving as a key indicator of insulation health. This study introduces a novel compact PD sensor assembly that integrates fiber Bragg grating (FBG) with an exponential acoustic horn to enhance the sensitivity of PD detection. The horn’s geometry effectively collects ultrasonic emissions from the PD, concentrating the acoustic energy to amplify the force on the FBG located at its focal point. To further enhance signal transduction, the FBG is mounted on a fixed solid structure engineered to resonate at higher ultrasonic frequencies that closely align with the dominant acoustic components generated by PD activity, ensuring improved strain amplification and optimal sensitivity. This results in measurable wavelength shifts, which are used for PD detection. A fiber Bragg grating analyzer interrogates the reflected spectra, providing real-time PD detection during HV operations. The effectiveness of the system was validated against the IEC 60270 standard method using laboratory models that emulated corona and surface discharge. The laboratory experiments demonstrated a significant sensitivity of 2.2 pm/Pa and a favorable signal-to-noise ratio of ~21 dB for the proposed sensor module. The dielectric construction of the sensor module, lightweight design, and resistance to electromagnetic interference make it suitable for harsh HV environments and the long-term condition monitoring of HV power equipment. Full article

A robust and cost-effective fiber-optic ultrasound sensor based on a slope-symmetric Fabry–Perot interferometer (FPI) is presented, employing dual-channel quadrature-biased heterodyne interrogation with an acousto-optic modulator (AOM). By introducing a 200 MHz frequency shift that yields an effective π/2 phase offset between the direct (unshifted) and frequency-shifted optical paths, the system ensures complementary sensitivity: when one channel operates at zero slope on the FPI transfer function (minimum sensitivity), the other resides at maximum slope, providing inherent immunity to laser wavelength drift and environmental perturbations. Experimental validation demonstrates reliable ultrasound detection across varying operating points. At quadrature extremes, one channel achieves peak amplitudes of ±2 V while the other is quiescent, whereas intermediate points enable simultaneous detection with amplitudes of ±1.5 V (AOM channel) and ±0.05–0.1 V (direct channel), accompanied by corresponding DC levels ranging from ~0.4 V to 1.6 V. The AOM channel utilizes simple envelope detection after 9.5–11.5 MHz bandpass filtering, maintaining low cost, though coherent mixing is suggested for enhanced weak-signal performance. The angle-symmetric FPI design, combined with gold-disk reflector adaptations and potential femtosecond laser micromachining, further reduces fabrication costs without sacrificing finesse or sensitivity. This quadrature-biased approach offers superior stability compared to single-channel systems, making it highly suitable for practical applications in photoacoustic imaging, nondestructive testing, and structural health monitoring. Full article

The echelle spectrometer utilizes an echelle grating as the primary dispersive element, combined with a prism or planar grating for cross-dispersion, to form a two-dimensional spectral image on an area-array Charge-Coupled Device (CCD). Compared with traditional spectrometers, this configuration provides superior spectral resolution, broader wavelength coverage, enhanced transient direct-reading capability, and higher energy throughput within a similar footprint. However, the use of area-array detectors significantly increases system cost, limiting adoption in cost-sensitive applications. To reduce cost while maintaining performance, we introduce a digital micromirror device (DMD) as a spatial light modulator to replace the traditional area-array detector, paired with a highly sensitive photomultiplier tube (PMT) for signal acquisition. The designed system operates across a wavelength range of 270 to 800 nm within a compact footprint of approximately 307 mm × 210 mm × 150 mm. The focused spot is accurately positioned on the DMD surface across the entire band, with the root mean square (RMS) spot radius smaller than a single micromirror’s size. Spectral information is efficiently coupled into the PMT via a focusing mirror by selectively flipping the DMD micromirrors for detection. Full article

Coherent-dispersion spectroscopy enables high-precision Doppler measurements of stellar spectral lines, which serves as a vital technique for the indirect detection of exoplanets. In this study, the post-dispersion system of a coherent-dispersion spectrometer (CODES) was designed and optimized using Zemax, with the detection spectral range of 656 nm–716 nm and a spectral resolution of 0.06 nm. The relay optical path adopted a combination of a cylindrical lens group and an image slicer, which reshaped the circular spot with a diameter of 630 μm into a linear spot of 27 μm × 2038.8 μm, effectively matching the slit size and improving the light throughput. A flat-field design was employed for the dispersion module, which adopted two structures: the Czerny–Turner spectrometer and the Dyson spectrometer. Both spectrometer structures were designed and optimized, and their aberrations and structural characteristics were comparatively analyzed. The on-axis Modulation Transfer Function (MTF) values at the central wavelength of the two spectrometers were 0.4@37 lp/mm and 0.8@37 lp/mm, respectively, and both the spectral resolution and imaging resolution could meet the design requirements. This work provides a feasible design idea for high-precision CODES for exoplanet detection as well as general medium-to-high resolution spectrometers. Full article

Thermally grown amorphous SiO₂ (a-SiO₂) on Si is widely used in microfluidic and biointerface devices, where surface charge governs capillary flows. We used amplitude-modulation Kelvin probe force microscopy (AM-KPFM) in air to test whether low-power visible light modulates a-SiO₂ surface potential and to derive mathematical charging-discharging models. Single-point contact potential difference (CPD) was recorded on ~0.6 µm p-type a-SiO₂ on p-type monocrystalline Si during repeated illumination cycles with continuous-wave diode lasers at 405, 505, and 685 nm delivered by optical fiber. The 405 and 505 nm wavelengths produced reproducible negative CPD shifts with steady-state values of ~−28 mV and ~−16 mV, while 685 nm stayed within noise (±2.5 mV). The 405 nm response followed bi-exponential kinetics with fast (tens of seconds) and slow (hundreds of seconds) components dominated by the slow process; after switch-off, CPD relaxed only from ~−28 to ~−23 mV over ~10³ s, indicating retention for ≥10³–10⁴ s. The 505 nm charging trace fit a single slower xponential, whereas discharging could not be fit robustly. These results demonstrate wavelength-dependent optical tuning of a-SiO₂ surface potential and provide compact kinetic descriptors for comparing charging, discharging, and retention. Full article

Clouds are a key factor affecting solar radiation, and their dynamic variations directly cause uncertainty and fluctuations in photovoltaic (PV) power output. To improve PV power prediction accuracy, this paper proposes an enhanced short-term photovoltaic power forecasting approach based on a hybrid neural network architecture using features extracted from satellite cloud images. First, a dual-layer image fusion method is developed for satellite cloud images from different wavelengths and spectral bands, effectively improving fusion accuracy. Second, texture descriptors derived from the Gray-Level Co-occurrence Matrix and multiscale information obtained via the wavelet transform are employed for feature extraction from fused images. Combined with a residual network (ResNet), an optical flow method, as well as an LSTM-based temporal modeling module, multidimensional features of the predicted cloud images are obtained. An improved Bayesian optimization (IBO) algorithm is then employed to derive the optimal fused features, thereby improving the matching between cloud image features and PV power. Third, an enhanced hybrid architecture integrating a convolutional neural network and long short-term memory units with a multi-head self-attention mechanism is developed. Numerical weather prediction (NWP) meteorological features are incorporated, and a tilted irradiance model is introduced to calculate the solar irradiance received by PV modules for use in near-term photovoltaic power forecasting. Finally, measurements collected at a photovoltaic power plant located in Hebei Province are used to validate the proposed method. The results show that, relative to the SA-CNN-MSA-LSTM and BO-CNN-LSTM models, the developed approach lowers the RMSE to an extent of 22.56% and 4.32%, while decreasing the MAE by 24.84% and 5.91%, respectively. Overall, the proposed model accurately captures the characteristics of predicted cloud images and effectively improves PV power prediction accuracy. Full article