Notes

Evaluation involving cold-start NO2 as well as NOx pollution levels, and the NO2/NOx ratio in a diesel-powered motor operated with assorted diesel-biodiesel integrates.
Traditional transmissive polarimetric methods can be used for wavelengths above 123 nm where birefringent materials transmit light and create significant birefringence. Below 123 nm, no suitable solution is known to measure the four Stokes parameters on a large wavelength range. Therefore, we study here an innovative reflective (rather than transmissive) polarimeter working in the far ultraviolet (FUV) range from 90 to 130 nm. We take advantage of the phase shift created by reflections as well as the different reflectivities for p (orthogonal ⊥) and s (parallel ∥ to the plane of incidence) polarizations to design an FUV polarimeter. Simulation of the analyzer and modulator using Mueller matrices coupled to polarimetric efficiencies calculations allowed optimization of reflective polarimeters for the first time, to the best of our knowledge. This opens up a new perspective for FUV polarimetry below 123 nm.Removal of a paint layer of 2024 aluminum alloy was studied using a nanosecond fiber pulsed laser with a maximum power of 30 W and the influence of laser cleaning energy density on the surface integrity of the substrate was explored. The cleaning energy density threshold of the paint layer is 17.69J/cm2 and the damage energy density threshold is 24.77J/cm2. The optimum cleanliness and surface integrity of laser cleaning were obtained when the energy density was 21.23J/cm2. Microhardness and Young's modulus of the surface after laser cleaning were improved by 6% and 25%, respectively. The mechanical properties of the surface of the substrate after laser cleaning were significantly improved, which is an advantage for this high-quality non-destructive cleaning technology of the aircraft skin surface paint layer.This work explores a theoretical solution for noise reduction in photonic systems using blackbody radiators. Traditionally, signal noise can be reduced by increasing the integration time during signal acquisition. However, increasing the integration time during signal acquisition will reduce the acquisition speed of the signal. By developing and applying a filter using a model based on the theoretical equations for blackbody radiation, the noise of the signal can be reduced without increasing integration time. In this work, three filters, extended Kalman filter, unscented Kalman filter (UKF), and extended sliding innovation filter (ESIF), are compared for blackbody photonic systems. The filters are tested on a simulated signal from five scenarios, each simulating different experimental conditions. In particular, the nonlinear filters, UKF and ESIF, showed a significant reduction of noise from the simulated signal in each scenario. The results show great promise for photonic systems using blackbody radiators that require post-process for noise reduction.Boresight and jitter are two fundamental pointing errors of laser illumination systems. A triangular-scanning algorithm is proposed to estimate the direction of the boresight via a three-step maximum boresight estimation and laser beam deflection procedure. TAS-120 On this basis, the closed-loop laser illumination (CLLI) for non-cooperative targets is realized, and the Cramer-Rao lower bounds (CRLB) performance in the lower limit of the pointing error is analyzed. Additionally, a Monte Carlo simulation system is built, and the performance of the CLLI algorithm is analyzed. link2 The simulation results demonstrate that the triangular-scanning algorithm has good performance and can accurately estimate the direction of the boresight to achieve CLLI. Further study shows that the simulation results agree well with theoretical estimations and approximate the CRLB at the lower limit.Due to its hardness, strength, and transparency, sapphire is an attractive material for the construction of microfluidic devices intended for high-pressure applications, but its physiochemical properties resist traditional microfabrication and bonding techniques. Here a femtosecond pulsed laser was used to directly machine fluidic channels within sapphire substrates and to form bonds between machined and flat sapphire windows, resulting in the creation of sealed microfluidic devices. Sapphire-sapphire bond strength was determined by destructive mechanical testing, and the integrity of the bond was verified by the capillary filling of the channel with air and ethanol. This combination of optical micromachining and bonding establishes a fully integrated approach to the fabrication of sapphire-based microfluidic systems.This publisher's note amends the author listing in Appl. link3 Opt.59, 8789 (2020)APOPAI0003-693510.1364/AO.402699.In this paper, we design a plasmonic perfect absorber based on black phosphorus (BP) with enhanced terahertz modulation. By tuning the chemical potential (μc) of BP, the modulation depth can reach up to 95%. The influence of geometric size and bandgap of BP on reflection spectra is also investigated. Moreover, the effect of the incident angle on the reflectance is discussed with different values of μc. Our results show that the plasmonic nanoslit mode contributes to the enhancement of the modulation effect. This simple periodical structure provides a potential route to design a tunable plasmonic BP-based modulator in the THz range.In dual or multiwavelength interferometry, the traditional equivalent wavelength method is widely used for phase recovery to enlarge the unambiguous measurement range (UMR). In fact, however, this method ignores information of size and sign (positive or negative) of single wavelength wrapped phases, and the extension of the UMR is not sufficient. For the reflective measurement, the largest UMR of the dual or multiwavelength interferometry is half of the least-common multiple (LCM) of single wavelengths, called the LCM effective wavelength, which is often several times the equivalent wavelength. But why do we often use the equivalent wavelength and seldom use the larger UMR in practice? Existing research reveals that the actual UMR is related to the measurement error of single-wavelength-wrapped phases, and half of the LCM effective wavelength is only the theoretical value. But how do errors affect the UMR? We think the quantitative analysis and description are lacking. In this paper, we continue to study this problem, analyze it in a graphical method, and give quantitative descriptions. The simulation experiments are carried out and verify our analysis.Three-dimensional (3D) vision plays an important role in industrial vision, where occlusion and reflection have made it challenging to reconstruct the entire application scene. In this paper, we present a novel 3D reconstruction framework to solve the occlusion and reflection reconstruction issues in complex scenes. A dual monocular structured light system is adopted to obtain the point cloud from different viewing angles to fill the missing points in the complex scenes. To enhance the efficiency of point cloud fusion, we create a decision map that is able to avoid the reconstruction of repeating regions of the left and right system. Additionally, a compensation method based on the decision map is proposed for reducing the reconstruction error of the dual monocular system in the fusion area. Gray-code and phase-shifting patterns are utilized to encode the complex scenes, while the phase-jumping problem at the phase boundary is avoided by designing a unique compensation function. Various experiments including accuracy evaluation, comparison with the traditional fusion algorithm, and the reconstruction of real complex scenes are conducted to validate the method's accuracy and the robustness to the shiny surface and occlusion reconstruction problem.The results of the rigorous calculation of mode fields in double adiabatic, single-mode etched-out optical fiber tapers coated with thin indium tin oxide films are discussed in the context of their application as environment refractive index sensors. It is shown that at only two particular thicknesses covering the homogeneous section of the taper ITO film about 100 nm and 177 nm, the lossy mode resonance is observed in the wavelength range of 1.50-1.55 µm. Moreover, the sensitivity of a sensor based on a 177 nm coating is significantly higher, and the resonance width is significantly lower than that of a sensor with a 100 nm coating. Optimal from the viewpoint of the figure of merit, values for the diameter of a homogeneous section of the etched fiber are defined.A few-mode fiber (FMF)-embedded long-period fiber grating is proposed as a sensor for simultaneous measurement of refractive index and temperature. Periodically embedding the FMFs induces the local refractive index modulation to achieve a compact sensor size and obtains a low insertion loss. The simulated results show that the two resonance dips have opposite waveguide dispersion coefficients. Therefore, they show different refractive indices and temperature sensitivities in the experiment. At the same time, the spectral characteristics of double-resonance dips provides a condition for simultaneous measurement of two parameters. By monitoring wavelength shift of the two dips, the simultaneous measurement of refractive index and temperature is easily realized.A practical interrogation scheme of a refractive index (RI) sensing system based on the abrupt fiber taper Mach-Zehnder interferometer sensor is designed, implemented, and demonstrated by experiment. The broadband light source and optical spectrum analyzer in the conventional design are replaced by two single-wavelength laser diodes modulated by a periodical square waveform and a simple photodetector (PD), which can significantly lower the cost and lead to easier integration. The photocurrent of the PD output signal is used as the indicator of the surrounding RI. Automatic data acquisition and processing is realized by LabVIEW programming. The experiment proves the feasibility of the new scheme and shows a high sensitivity (2371 mV/RIU) and high stability.This paper presents a scanning system that integrates a chromatic confocal displacement sensor for topography measurement of a surface. To take an advantage of its compactness and reliability, an off-the-shelf chromatic confocal displacement sensor is integrated. Instead of moving the sensor, a galvanometer scanner reflects the optical point to increase the scan speed, and fast and accurate scanning motion is realized by learning without a model. The resulting images are corrected based on a geometric model to compensate for image distortion.Editor-in-Chief Ron Driggers reports on some key indicators of Applied Optics' success.This publisher's note corrects an equation in Appl. Opt.59, 8314 (2020)APOPAI0003-693510.1364/AO.396709.To derive the impact of chip size reduction on optical efficiency in micro-LED array panels, blue InGaN/GaN LEDs, which consist of 21×7 arrays (60 ppi display) with different mesa sizes on sapphire substrates, are designed and fabricated in this study. Changing the mesa area of the chip is first proposed to investigate the luminous efficiency (cd/A) of the screen. The current efficiency with a peak wavelength of 450 nm reaches up to 14.29 cd/A for the biggest pixel 50µm×60µm and to 12.25 cd/A for the 15µm×25µm chip, delivering high-level efficiencies to the current LED research field. The mechanisms of size-dependent efficiency variation trends and efficiency droops of blue LEDs are investigated experimentally, confirming that the current efficiency is more efficient at high injection current density while exhibiting poorer performance at the low current density region for smaller chips. The peak efficiency corresponds to higher current density with a decrease in chip size according to the carrier recombination ABC model.
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