We employ a hybrid machine learning method in this paper, starting with OpenCV for initial localization, then refining the result with a convolutional neural network model built upon the EfficientNet architecture. The proposed localization method is compared against OpenCV's unrefined locations, and against an alternative refinement method stemming from traditional image processing strategies. We observe that both refinement methods produce an approximate 50% decrease in the mean residual reprojection error under optimal imaging conditions. The traditional refinement method, applied to images under unfavorable conditions—high noise and specular reflection—leads to a degradation in the results obtained through the use of pure OpenCV. This degradation amounts to a 34% increase in the mean residual magnitude, equivalent to 0.2 pixels. In comparison to OpenCV, the EfficientNet refinement demonstrates a robust performance in less-than-ideal conditions, resulting in a 50% reduction in the mean residual magnitude. read more In light of this, the refined feature localization of EfficientNet enables a wider variety of workable imaging positions across the entire measurement volume. This process, therefore, facilitates more robust estimations of camera parameters.
Breath analyzer models encounter a substantial challenge in detecting volatile organic compounds (VOCs), particularly due to their extremely low concentrations (parts-per-billion (ppb) to parts-per-million (ppm)) and the high humidity levels associated with exhaled breath. Gas species and their concentrations play a crucial role in modulating the refractive index, a vital optical characteristic of metal-organic frameworks (MOFs), and making them usable for gas detection applications. We πρωτοποριακά applied Lorentz-Lorentz, Maxwell-Garnett, and Bruggeman effective medium approximation equations to calculate the percentage change in refractive index (n%) of ZIF-7, ZIF-8, ZIF-90, MIL-101(Cr), and HKUST-1 porous materials exposed to ethanol at varying partial pressures for the first time. The storage capacity of MOFs and the selectivity of biosensors were evaluated by determining the enhancement factors of the designated MOFs, especially at low guest concentrations, through their guest-host interactions.
Visible light communication (VLC) systems employing high-power phosphor-coated LEDs struggle to maintain high data rates, directly impacted by the narrow bandwidth and the slow speed of yellow light. In this paper, we propose a novel transmitter, utilizing a commercially available phosphor-coated LED, to accomplish a wideband VLC system that does not necessitate a blue filter. The transmitter's design incorporates a folded equalization circuit and a bridge-T equalizer. The bandwidth of high-power LEDs is expanded more substantially thanks to the folded equalization circuit, which employs a novel equalization scheme. Employing the bridge-T equalizer to reduce the slow yellow light output from the phosphor-coated LED is a better approach than using blue filters. The 3 dB bandwidth of the VLC system, built with the phosphor-coated LED and enhanced by the proposed transmitter, was significantly expanded, going from several megahertz to 893 MHz. As a result of its design, the VLC system enables real-time on-off keying non-return to zero (OOK-NRZ) data transmission at rates up to 19 gigabits per second at a distance of 7 meters, maintaining a bit error rate (BER) of 3.1 x 10^-5.
A terahertz time-domain spectroscopy (THz-TDS) system, with high average power, is presented. This system leverages optical rectification in a tilted pulse front geometry within lithium niobate, at room temperature, and is driven by a commercial, industrial femtosecond laser offering variable repetition rates from 40 kHz to 400 kHz. Our time-domain spectroscopy (TDS) setup can investigate repetition rate-dependent effects, thanks to the driving laser's consistent 41 joule pulse energy at a 310 femtosecond pulse duration for all repetition rates. Employing a maximum repetition rate of 400 kHz, our THz source is capable of accepting up to 165 watts of average power input. This input yields an average output THz power of 24 milliwatts, having a conversion efficiency of 0.15% and an electric field strength of several tens of kilovolts per centimeter. Our TDS's pulse strength and bandwidth remain consistent at the other, lower repetition rates, showing no effect on the THz generation from thermal effects within this average power region, encompassing several tens of watts. Spectroscopic applications find a strong allure in the combination of a potent electric field, flexible operation at high repetition rates, specifically because the system's compact industrial laser operates without requiring auxiliary compressors or pulse manipulation devices.
By leveraging a grating-based interferometric cavity, a coherent diffraction light field is produced in a compact format, making it a strong candidate for displacement measurement applications due to both its high level of integration and high degree of accuracy. Diffractive optical elements, combined in phase-modulated diffraction gratings (PMDGs), effectively suppress zeroth-order reflected beams, leading to improved energy utilization and heightened sensitivity in grating-based displacement measurements. While conventional PMDGs incorporating submicron-scale features are often employed, their production necessitates sophisticated micromachining methods, thus posing a considerable manufacturing hurdle. Employing a four-region PMDG, this paper develops a hybrid error model that combines etching and coating errors, thus quantitatively analyzing the correlation between these errors and optical responses. The experimental verification of the hybrid error model and the process-tolerant grating is achieved by means of micromachining and grating-based displacement measurements, utilizing an 850nm laser, confirming their validity and effectiveness. The PMDG's innovation results in a near 500% improvement in the energy utilization coefficient (calculated as the ratio of the peak-to-peak value of the first-order beams to the zeroth-order beam) and a four-fold reduction in zeroth-order beam intensity when assessed against conventional amplitude gratings. Primarily, the PMDG maintains unusually lenient process standards, allowing deviations in etching and coating processes up to 0.05 meters and 0.06 meters, respectively. This method provides compelling alternatives to the manufacturing of PMDGs and grating devices, exhibiting exceptional compatibility across a range of procedures. Through a systematic study, the influence of fabrication imperfections on the optical properties of PMDGs, and the associated interplay between these errors and response, are investigated for the first time. With the hybrid error model, possibilities for diffraction element fabrication are extended, thus circumventing the practical limitations imposed by micromachining fabrication.
InGaAs/AlGaAs multiple quantum well lasers, grown by molecular beam epitaxy on silicon (001) substrates, have been successfully demonstrated. InAlAs trapping layers, seamlessly incorporated within AlGaAs cladding layers, efficiently relocate misfit dislocations from their location in the active region. The same laser structure, minus the InAlAs trapping layers, was also developed for a comparative analysis. read more The process of fabricating Fabry-Perot lasers involved using the as-grown materials, all having a 201000 square meter cavity. A laser incorporating trapping layers achieved a 27-fold reduction in threshold current density under pulsed operation (5-second pulse width, 1% duty cycle), compared to the control device. Subsequently, this same design facilitated room-temperature continuous-wave lasing with a threshold current of 537 mA, a figure corresponding to a threshold current density of 27 kA/cm². Given an injection current of 1000mA, the single-facet maximum output power observed was 453mW, and the corresponding slope efficiency was 0.143 W/A. Monolithic growth of InGaAs/AlGaAs quantum well lasers on silicon substrates is demonstrated in this work to yield substantially enhanced performance, thereby offering a feasible solution for optimization of the InGaAs quantum well design.
This paper comprehensively explores micro-LED display technology, with particular attention to the laser lift-off process for sapphire substrates, photoluminescence detection, and the significance of size-dependent luminous efficiency. Following laser irradiation, the thermal decomposition process of the organic adhesive layer is thoroughly examined. The decomposition temperature of 450°C, derived from the one-dimensional model, demonstrates high consistency with the inherent decomposition temperature characteristics of the PI material. read more The peak wavelength of photoluminescence (PL) is red-shifted by about 2 nanometers relative to electroluminescence (EL) while maintaining a higher spectral intensity under the same excitation conditions. Size-dependent investigations of device optical-electric characteristics reveal a critical finding: as device size decreases, luminous efficiency drops while power consumption increases under the same display resolution and PPI.
For the determination of specific numerical values for parameters resulting in the suppression of several lowest-order harmonics of the scattered field, we propose and develop a novel rigorous technique. Encompassing a perfectly conducting cylinder with a circular cross-section, and partially obscuring it, are two layers of dielectric, demarcated by an infinitely thin impedance layer; this constitutes a two-layer impedance Goubau line (GL). A rigorous approach to the development of the method allows for closed-form determination of the parameters that produce the cloaking effect, achieved specifically through suppressing multiple scattered field harmonics and varying the sheet impedance. This process avoids numerical calculation. The novelty of this completed research lies in this particular issue. A benchmark for validating the results of commercial solvers can be provided by this advanced technique, which is applicable across virtually all parameter ranges. Calculating the cloaking parameters is a simple process, requiring no computations. A detailed visualization and analysis of the partial cloaking is performed by our team. The developed parameter-continuation technique provides a means to increase the number of suppressed scattered-field harmonics, contingent upon the impedance's selection.