Search Results (1,251)

The nitrogen-vacancy (NV) center magnetic sensor, leveraging nitrogen-vacancy quantum effects, enables high-sensitivity magnetic field detection via optically detected magnetic resonance (ODMR). However, conventional single-point integrated devices suffer from limitations such as inefficient regional magnetic field detection and challenges in discerning the directional variations of dynamic magnetic fields. To address these issues, this study proposes an array- based architecture that innovatively substitutes the conventional 532 nm laser with quantum-dot light-emitting diodes (QLEDs). Capitalizing on the advantages of QLEDs—including compatibility with micro/nano-fabrication processes, wavelength tunability, and high luminance—a 2 × 2 monolithically integrated magnetometer array was developed. Each sensor unit achieves a magnetic sensitivity of below 26 nT·Hz^−1/2 and a measurable range of ±120 μT within the 1–10 Hz effective bandwidth. Experimental validation confirms the array’s ability to simultaneously resolve multi-regional magnetic fields and track dynamic field orientations while maintaining exceptional device uniformity. This advancement establishes a scalable framework for the design of large-scale magnetic sensing arrays, demonstrating significant potential for applications requiring spatially resolved and directionally sensitive magnetometry. Full article

This work presents a proof of concept for a short-range high spectral resolution lidar (SR-HSRL) optimized for aerosol characterization in the first kilometer of the atmosphere. The system is based on a compact, high-repetition-rate diode-based fiber laser with a 300 MHz linewidth and 5 ns pulse duration, coupled with an iodine absorption cell. A central challenge in the instrument’s development was identifying a laser source that offered both sufficient spectral resolution for HSRL retrievals and nanosecond pulse durations for high spatiotemporal resolution, while also being compact, tunable, and cost-effective. To address this, we developed a methodology for complete spectral and temporal laser characterization. A two-day field campaign conducted in July 2024 in Tsukuba, Japan, validated the system’s performance. Despite the relatively broad laser linewidth, we successfully retrieved aerosol backscatter coefficient profiles from 50 to 1000 m, with a spatial resolution of 7.5 m and a temporal resolution of 6 s. The results demonstrate the feasibility of using SR-HSRL for detailed studies of aerosol layers, cloud interfaces, and aerosol–cloud interactions. Future developments will focus on extending the technique to ultra-short-range applications (<100 m) from ground-based and mobile platforms, to retrieve aerosol extinction coefficients and lidar ratios to improve the characterization of near-source aerosol properties and their radiative impacts. Full article

Narrow-linewidth broadband tunable external cavity diode lasers (NBTECDLs), with their broadband tuning range, narrow linewidth, high side-mode suppression ratio (SMSR), and high output power, have become important laser sources in many fields such as optical communication, spectral analysis, wavelength division multiplexing systems, coherent detection, and ultra-high-speed optical interconnection. This paper briefly describes the basic theory of NBTECDLs, introduces NBTECDLs with diffraction grating type, fiber Bragg grating (FBG) type, and waveguide type, and conducts an in-depth analysis on the working principles and performance characteristics of NBTECDLs based on different NBTECDL types. Then, it reviews the latest research progress on Littrow-type, Littman-type, FBG-type, and waveguide-type NBTECDLs in detail and compares and summarizes the characteristics of Littrow-type NBTECDLs, Littman-type NBTECDLs, FBG-type NBTECDLs, and waveguide-type NBTECDLs. Finally, it looks at the structural features, key technologies, optical performance, and application fields of the most cutting-edge research in recent years and summarizes the challenges and future development directions of NBTECDLs. Full article

Background: This case series study aims to evaluate the spontaneous eruption of impacted canines following diode laser disinclusion surgery without orthodontic traction, and to analyze the correlation with five prognostic factors: age, sex of the patient, angle α, sector, and height of inclusion of the canine. Methods: The sample included 15 patients aged 13–30 years and 20 palatally impacted canines. The patients’ records were collected, and prognostic factors were assessed. All patients underwent disinclusion surgery using a diode laser (K-Laser, Eltech, Blue Derma) and post-surgery, canines were monitored with intraoral scans and photos at 1 week, 8 weeks (T1), and 16 weeks (T2). The STL files were superimposed with the open-source software MeshLab (MeshLab 2023.12, Visual Computing Lab, Pisa, Italy), and the eruption values were measured. Through multiple linear regression analysis, the relationships between the five prognostic factors and the total spontaneous eruption value were analyzed. Results: The canines treated in this study responded with an average eruption of 4.70 mm. For the prognostic factors sex (p = 0.94) and angle α (p = 0.12), no statistically significant relationship with eruption was found. The variables age (p < 0.001), sector II (p = 0.02), sector III (p = 0.03), sector IV (p = 0.06), and inclusion height (p < 0.001) had negative linear coefficients. Consequently, as the values of these three prognostic factors increased, a lower eruption of the included element measured in millimeters was obtained. Conclusions: All canines successfully erupted following the disinclusion procedure, avoiding the use of orthodontic traction. Patient sex and the α angle of impaction were not reliable predictors of eruption outcomes. In contrast, age, sector, and inclusion height measured via CBCT showed high statistical significance and could be used as prognostic factors to predict the eruptive response following disinclusion surgery. Full article

Photobiomodulation (PBM) harnesses near-infrared (NIR) light to stimulate cellular processes, offering non-invasive treatment options for a range of conditions, including chronic wounds, inflammation, and neurological disorders. NIR light-emitting diodes (LEDs) are emerging as safer and more scalable alternatives to conventional lasers, but optimizing their performance for clinical use remains a challenge. This perspective explores the latest advances in NIR-emitting materials, spanning Group III–V, IV, and II–VI semiconductors, organic small molecules, polymers, and perovskites, with an emphasis on their applicability to PBM. Particular attention is given to the promise of perovskite LEDs, including lead-free and lanthanide-doped variants, for delivering narrowband, tunable NIR emission. Furthermore, we examine photonic and plasmonic engineering strategies that enhance light extraction, spectral precision, and device efficiency. By integrating advances in materials science and nanophotonics, it is increasingly feasible to develop flexible, biocompatible, and high-performance NIR LEDs tailored for next-generation therapeutic applications. Full article

Background/Objectives: The laser beam absorption and thermal relaxation time (TRT) in oral tissues are key to optimizing treatment parameters. The aim of this study is to (1) evaluate, in an ex vivo study, the percentage of attenuation and transmittance of each wavelength as a function of tissue thickness; (2) determine the global absorption coefficient, α, of pig gingival tissue for the most commonly used wavelengths in dentistry; (3) calculate the thermal relaxation time (TRT) of oral tissue for these wavelengths; and (4) determine their corresponding penetration depths. Methods: We measured the transmission of different laser wavelengths through pig oral gingival tissues (Mandibular labial gingiva). We placed each tissue sample between two glass slides with minimal light attenuation. The input and output powers were measured after irradiating the tissue at different specific wavelengths: 450 nm, 480 nm, 532 nm, 632 nm, 810 nm, 940 and 980 nm, 1064 nm, 1341, 2780 nm and 2940 nm. After calculating the transmittance values, we plotted transmittance curves for each wavelength. Using the Beer–Lambert law, we then calculated the absorption coefficient (α) of each wavelength in the oral gingival tissue. Absorption coefficients were then used to calculate the TRT and penetration depth for each wavelength. Results: Among the tested wavelengths, 810 nm exhibited the lowest absorption in ex vivo porcine gingival tissue (α = 9.60 cm⁻¹). The 450 nm blue laser showed moderate absorption (α = 26.8 cm⁻¹), while the Er:YAG laser at 2940 nm demonstrated the highest absorption (α = 144.8 cm⁻¹). We ranked the wavelengths from most absorbed to least absorbed by porcine oral gingival mucosa as follows: 2940 nm > 2780 nm > 450 nm > 480 nm > 532 nm > 1341 nm > 632 nm > 940 nm > 980 nm > 1064 nm > 810 nm. Conclusions: Absorption and the TRT vary significantly across wavelengths. Erbium lasers are characterized by the highest absorption and minimal light penetration. Infrared diodes, particularly the 810 nm wavelength, showed the lowest absorption and deepest tissue penetration and exhibited the highest thermal relaxation time. The 480 nm laser demonstrated greater absorption by porcine gingival tissue compared to the 532 nm laser. These findings provide evidence-based guidance for wavelength selection in dental treatments and photobiomodulation, enabling improved precision, safety, and therapeutic efficacy in clinical practice. Full article

This in vivo animal study aimed to evaluate the effects of two different implant placement micromotor systems on implant stability and removal torque. In a within-animal crossover design, twenty titanium implants (AnyOne fixture; internal type; diameter, 3.5 mm; length, 7.0 mm; Megagen, Daegu, Republic of Korea) were placed in the tibiae of five rabbits using a conventional micromotor system (NSK group: SurgicPro+; NSK, Kanuma, Japan) and a diode laser-integrated micromotor system (SAESHIN group: BLP 10; Saeshin, Daegu, Republic of Korea). Resonance frequency analysis provided the implant stability quotient (ISQ) immediately after placement and at four weeks. Micro-computed tomography quantified the bone–implant interface gap (BIG). Removal torque was measured at sacrifice. Linear mixed-effects models with a random intercept for rabbit generated adjusted means with 95% confidence intervals (CIs) (α = 0.05). Equivalence for the four-week ISQ used two one-sided tests with a margin of ±5 ISQ. The SAESHIN group achieved a higher immediate ISQ than the NSK group (difference =+6.9 ISQ; 95% CI +1.3–+12.5; p = 0.018). At four weeks, the ISQ did not differ (difference = −1.2 ISQ; 95% CI −4.3–+1.9; p = 0.42), and equivalence was supported (TOST p_lower = 0.024; p_upper = 0.019). Removal torque was comparable (difference = +4.3 N·cm; 95% CI −5.2–+13.8; p = 0.36). BIG metrics showed no between-system differences across regions. ICC indicated clustering for ISQ and torque (0.36 and 0.31). The diode laser-integrated micromotor system yielded a higher immediate ISQ under a standardized 35 N·cm seating torque, whereas the ISQ, removal torque, and BIG at four weeks were comparable to those of the conventional system. The immediate ISQ should be interpreted as stiffness under fixed torque rather than superior device-dependent interlocking. These findings support the clinical interchangeability of the two systems for early osseointegration endpoints in preclinical settings. Full article

Native defects significantly impair the electro-optical performance of GaInN/GaN-based light-emitting diodes (LEDs). Therefore, precise characterization of their properties, such as energy levels, capture kinetics, capture cross-sections, and spatial distributions, is crucial for understanding their physical origins following improvement in performance. However, modeling the impact of various defects on the electrical and optical characteristics of LEDs still remains a complex challenge. This study proposes a laser-based measurement technique for the accurate localization and screening of defects in GaInN/GaN-based LEDs by establishing a correlation model between laser excitation and defect response, which enables real-time monitoring of defect dynamics during device degradation, while simultaneously evaluating the effects of the defect state dynamics on the electro-optical characteristics of LED devices. The experimental results indicate that defects located at different spatial positions lead to distinct degradation mechanisms. Full article

Background and Clinical Significance: Cervical ectopic pregnancy (CEP) is a rare and potentially serious condition, in which the embryo implants within the cervical canal rather than the uterine cavity and is present in less than 1% of all ectopic pregnancies. There are different treatment options depending on the particular situation and the woman’s reproductive desire but conservative approaches as the first line of treatment is preferred in all cases and hysteroscopic resection of the fetus is one of these options. Several types of laser systems are available for use in hysteroscopic surgery, including neodymium:YAG (Nd:YAG) lasers, KTP and Argon lasers, as well as diode lasers. The holmium:YAG (Ho:YAG) laser, although more commonly used in urology due to its ability to cut, coagulate, and vaporize tissue, has gained interest in gynecologic procedures because of its precision and favorable safety profile. Case Presentation: We present the case of a 32-year-old woman, pregnant for the first time, who was diagnosed with CEP and successfully treated using a Ho:YAG laser during an outpatient hysteroscopic procedure. As far as we know, this is the first published case using this approach. Conclusions: The Ho:YAG laser is a proven tool for outpatient hysteroscopic procedures like septum and adhesion removal. Its ability to both cut and coagulate offers a minimally invasive, fertility-sparing option for managing cervical ectopic pregnancy. With the right patient and proper backup plans in place, this approach could be a promising alternative to more aggressive treatments. Full article

This paper proposes an automatic power and modulation control (APMC) circuit that can directly detect the degradation of vertical cavity surface emitting laser (VCSEL) diodes by utilizing a novel voltage sensing mechanism, thereby eliminating the need for costly external monitoring photodiodes. Notably, the proposed APMC architecture facilely observes the performance degradation by sampling the voltage values at the upper node of the VCSEL diode during both modulation on and off states. The APC loop can perceive a 25 mV voltage drop that corresponds to a 0.5 mA increase in the threshold current, providing a 4-bit digital switch signal. Thereafter, it is delivered to the VCSEL diode driver to initiate compensation of the bias current. In the AMC loop, a 50 mV voltage drop equivalent to a 1 mA reduction in the modulation current is similarly detected to produce another 4-bit digital code. The proposed APMC IC is designed by using a 180 nm CMOS process and consumes a total power of 18.2 mW from a single 3.3 V supply. Full article

High-power laser diodes (LDs) inherently generate considerable heat during current loading, which presents substantial challenges to the stable operation of laser systems. This study reports a machine learning-based approach that is to be applied to LD temperature control systems, in which a fuzzy neural network (FNN) algorithm is integrated with a proportional-integral-derivative (PID) controller to create an FNN-PID control architecture. The proposed algorithms synergistically integrate fuzzy rule-based systems with neural network learning frameworks, and, furthermore, facilitate adaptive parameter optimization while preserving the interpretability of the decision-making process. Applying the optimized algorithm temperature controller to the LD with output optical power of 110 W @ 888 nm, compared with the conventional PID, the FNN-PID algorithm has shortened the temperature settling time by 77% during 100 W heat generation in LD, the long-term temperature fluctuation is decreased from ±0.126% to ±0.06%, the corresponding optical power steady-state precision is decreased from ±0.09% to ±0.04%, and the step response time of temperature and corresponding power are reduced by 73.4% and 70% from 25 °C to 27 °C, respectively. The FNN-PID outperforms conventional methods (the PID algorithm and the Fuzzy-PID algorithm) in managing thermal fluctuations, and it offers potential for precise laser control applications to enhance beam quality and stability. Full article

This study presents a compact reconfigurable asymmetric unit cell designed for millimeter-wave (mm-wave) transmit array (TA) antennas. Despite its compact size, the proposed unit cell achieves a broad bandwidth and low insertion loss. By breaking the symmetry of the unit cell and by implementing two MA4AGP910 pin diodes in the proposed unit cell, a phase difference of 180 degrees (1-bit configuration) is obtained in a wide frequency band. The unit cell is fabricated using an LPKF laser machine and characterized using WR-34 waveguide. Measurement results closely match those obtained by simulations, confirming the design’s accuracy. With these functionalities, the proposed 1-bit unit cell emerges as a promising candidate for mm-wave transmit array antennas. Full article

Wavelength modulation-tunable diode laser absorption spectroscopy (WM-TDLAS) is a critical tool for gas detection. However, noise in second harmonic signals degrades detection performance. This study presents a hybrid denoising algorithm combining Empirical Mode Decomposition (EMD) and wavelet adaptive thresholding to enhance WM-TDLAS performance. The algorithm decomposes raw signals into intrinsic mode functions (IMFs) via EMD, selectively denoises high-frequency IMFs using wavelet thresholding, and reconstructs the signal while preserving spectral features. Simulation and experimental validation using the CH₄ absorption spectrum at 1654 nm demonstrate that the system achieves a threefold improvement in detection precision (0.1181 ppm). Allan variance analysis revealed that the detection capability of the system was significantly enhanced, with the minimum detection limit (MDL) drastically reduced from 2.31 ppb to 0.53 ppb at 230 s integration time. This approach enhances WM-TDLAS performance without hardware modification, offering significant potential for environmental monitoring and industrial safety applications. Full article

Background/Objectives: This study aimed to evaluate the efficacy of a 445 nm diode laser in enhancing enamel resistance to acid-induced demineralization and to investigate the associated compositional and structural modifications using scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA), and X-ray diffraction (XRD) crystallographic analysis. Methods: A total of 126 extracted human teeth were used. A total of 135 (n = 135) enamel discs (4 × 4 mm) from 90 teeth were assigned to either a laser-irradiated group or an untreated control group for SEM, ESCA, and XRD analyses. Additionally, 24 mono-rooted teeth were used to measure pulp temperature changes during laser application. Laser irradiation was performed using a 445 nm diode laser with a pulse width of 200 ms, a repetition rate of 1 Hz, power of 1.25 W, an energy density of 800 J/cm², a power density of 3980 W/cm², and a 200 µm activated fiber. Following acid etching, SEM was conducted to assess microstructural and ionic alterations. The ESCA was used to evaluate the Ca/P ratio, and XRD analyses were performed on enamel powders to determine changes in phase composition and crystal lattice parameters. Results: The laser protocol demonstrated thermal safety, with minimal pulp chamber temperature elevation (0.05667 ± 0.04131 °C). SEM showed that laser-treated enamel had a smoother surface morphology and reduced acid-induced erosion compared with controls. Results of the ESCA revealed no significant difference in the Ca/P ratio between groups. XRD confirmed the presence of hydroxyapatite structure in laser-treated enamel and detected an additional diffraction peak corresponding to a pyrophosphate phase, potentially enhancing acid resistance. Results of the spectral analysis showed the absence of α-TCP and β-TCP phases and a reduction in the carbonate content in the laser group. Furthermore, a significant decrease in the a-axis lattice parameter suggested lattice compaction in laser-treated enamel. Conclusions: Irradiation with a 445 nm diode laser effectively enhances enamel resistance to acid demineralization. This improvement may be attributed to chemical modifications, particularly pyrophosphate phase formation, and structural changes including prism-less enamel formation, surface fusion, and decreased permeability. These findings provide novel insights into the mechanisms of laser-induced enhancement of acid resistance in enamel. Full article

Whispering-gallery-mode (WGM) microresonators are amongst the most promising optical sensors for detecting bio-chemical targets. A number of laser interrogation methods have been proposed and demonstrated over the last decade, based on scattering and absorption losses or resonance splitting and shift, harnessing the high-quality factor and ultra-small volume of WGMs. Actually, regardless of the sensitivity enhancement, their practical sensing operation may be hampered by the complexity of coupling devices as well as the signalprocessing required to extract the WGM response. Here, we use a silica microsphere immersed in an aqueous environment and efficiently excite optical WGMs with a free-space visible laser, thus collecting the relevant information from the transmitted and back-scattered light without any optical coupler, fiber, or waveguide. We show that a 640-nm diode laser, actively frequency-locked on resonance, provides real-time, fast sensing of dielectric nanoparticles approaching the surface with direct analog readout. Thanks to our illumination scheme, the sensor can be kept in water and operate for days without degradation or loss of sensitivity. Diverse noise contributions are carefully considered and quantified in our system, showing a minimum detectable particle size below 1 nm essentially limited by the residual laser microcavity jitter. Further analysis reveals that the inherent laserfrequency instability in the short, -mid-term operation regime sets an ultimate bound of 0.3 nm. Based on this work, we envisage the possibility to extend our method in view of developing new viable approaches for detection of nanoplastics in natural water without resorting to complex chemical laboratory methods. Full article