Single Line Scan Research Articles

Bending Forming Characteristics of CoCrFeMnNi High-Entropy Alloy Sheets Induced by Nanosecond Pulse Laser Irradiation.

Laser bending forming, as a flexible and die-less forming approach, facilitates the three-dimensional shaping of sheets through the generation of thermal stress via laser-material interaction. In this study, the bending forming characteristics of CoCrFeMnNi high-entropy alloy sheets induced by nanosecond pulse laser irradiation were systematically investigated. The effects of parameters including laser power, scanning speed, number of scans, scanning interval, and sheet size on the bending angle, cross-sectional morphology, and hardness were studied in detail under both the laser single-line and multi-line scanning modes. The experimental results confirmed the effectiveness of nanosecond pulse laser irradiation for achieving accurate formation of CoCrFeMnNi sheets, with the successful fabrication of J, L, and U-shaped metal components. Apart from the forming ability, the cross-sectional hardness was significantly increased due to the grain refinement effect of nanosecond pulse laser irradiation. Furthermore, employing the laser single-line scanning mode enabled the effective rectification of overbending parts, showcasing complete recovery for small-angle overbending, and a remarkable 91% recovery for larger-angle overbending. This study provides an important basis for the bendability of CoCrFeMnNi sheets by laser forming and elucidates the evolution of the microstructure and mechanical properties in the bending region.

Numerical Study of Temperature Field and Melt Pool Properties during Electron Beam Selective Melting Process with Single Line and Multiple Line Scanning

Numerical Study of Temperature Field and Melt Pool Properties during Electron Beam Selective Melting Process with Single Line and Multiple Line Scanning

Development of optimal L-PBF process parameters using an accelerated discrete element simulation framework

Laser Powder Bed Fusion (L-PBF) has immense potential for the production of complex, lightweight, and high-performance components. The traditional optimization of process parameters is costly and time-intensive, due to reliance on experimental approaches. Current numerical analyses often model single-line scans, while it is necessary to model multiple fully scanned layers to optimize for bulk material quality. Here, we introduce a novel approach utilizing discrete element simulations with a ray tracing-modeled laser heat source. Our approach significantly reduces the cost and time consumption compared to conventional optimization methods. GPU acceleration enables efficient simulation of multiple layers, resulting in parameters optimized for bulk material. In a case study, parameters were optimized for AlSi10Mg in just 5 days, a process that would have taken over 8 months without GPU acceleration. Experimental validation affirms the quality of the optimized process parameters, achieving an optical density of 99.91%.Graphical Optimization using the accelerated simulation yielded an optimized parameter set within 5 days. This resulted in apart with an optical density of 99.91%.

Intergranular stress and plastic strain formation during laser scanning of additively manufactured stainless steel: An experimentally-driven thermomechanical simulation study

A novel experiment-driven modelling and simulation approach is proposed to study the formation of intergranular stresses and plastic strains during laser scanning of additively manufactured 316L stainless steel. Recently, laser scanning experiments were performed using a unique coupling between a continuous-wave laser and a scanning electron microscope. These experiments form the basis for the development of a thermo-elasto-viscoplastic polycrystal model endowed with the minimum necessary physics of the problem in order to facilitate simulating sufficiently large domains to obtain reasonable stress magnitudes. The case of a single laser line scan performed in vacuum is analyzed in detail. Polar dislocation density magnitudes and distribution predicted from the simulation are compared with those measured experimentally. Results reveal that for 93% of the grains in the lasered zone, a statistical measure of the predicted polar dislocation density (Nye’s) tensor lies within a factor of 2 (higher or lower) of the experimental one; this result sets a benchmark for future experiment-simulation comparisons. Subsequent investigation studies the origin of the local residual stresses and plastic strains. On the lasered surface, the grain surface-averaged normal residual stress component and plastic strain component along the scan direction reaches a value ∼1.7GPa and 0.04, respectively. The contribution of elastic anisotropy, plastic heterogeneity and strengthening due to microstructure refinement after laser scanning on the formation of stresses and plastic strains is studied in detail.

Glaucoma detection model by exploiting multi-region and multi-scan-pattern OCT images with dynamical region score.

Currently, deep learning-based methods have achieved success in glaucoma detection. However, most models focus on OCT images captured by a single scan pattern within a given region, holding the high risk of the omission of valuable features in the remaining regions or scan patterns. Therefore, we proposed a multi-region and multi-scan-pattern fusion model to address this issue. Our proposed model exploits comprehensive OCT images from three fundus anatomical regions (macular, middle, and optic nerve head regions) being captured by four scan patterns (radial, volume, single-line, and circular scan patterns). Moreover, to enhance the efficacy of integrating features across various scan patterns within a region and multiple regional features, we employed an attention multi-scan fusion module and an attention multi-region fusion module that auto-assign contribution to distinct scan-pattern features and region features adapting to characters of different samples, respectively. To alleviate the absence of available datasets, we have collected a specific dataset (MRMSG-OCT) comprising OCT images captured by four scan patterns from three regions. The experimental results and visualized feature maps both demonstrate that our proposed model achieves superior performance against the single scan-pattern models and single region-based models. Moreover, compared with the average fusion strategy, our proposed fusion modules yield superior performance, particularly reversing the performance degradation observed in some models relying on fixed weights, validating the efficacy of the proposed dynamic region scores adapted to different samples. Moreover, the derived region contribution scores enhance the interpretability of the model and offer an overview of the model's decision-making process, assisting ophthalmologists in prioritizing regions with heightened scores and increasing efficiency in clinical practice.

A holistic approach for evaluation of Gaussian versus ring beam processing on structure and properties in laser powder bed fusion

In this study, a holistic evaluation strategy employing a complex test artifact, coupled with single line scan tracks, was employed to examine the influence of different laser beam energy profiles on various features of laser-based powder bed fusion of metals (PBF-LB/M). Using IN718, results revealed a significant influence of the laser beam on bead geometry. Specifically, the conventional Gaussian beam produced deeper, concave-shaped melt pools, while the ring beam resulted in wider and shallower beads. In terms of productivity, the artifacts (two each) fabricated using the Gaussian beam required 6 h and 6 min of build time, while those built using ring beam required only 3 h and 49 min (37% build time reduction) but a defocused Gaussian beam (not included in this study) can match the productivity of the ring beam. However, the holistic approach using the complex test artifact highlighted drawbacks associated with the ring beam, including increased lack of fusion porosity, compromised resolution for features below 0.5 mm, and less than 10% elongation to break in both as built and heat-treated conditions. While acknowledging the potential for improvement through further process optimization, the study concludes that the shallower melt pools produced by the ring beam may cause limitations as layer thicknesses increase. Microstructural analysis revealed distinct grain characteristics, with the Gaussian beam producing more equiaxed grains and the ring beam favouring columnar grains positioned along the build direction. The work primarily highlights the need for and benefits from a holistic analysis in PBF-LB/M technology, ensuring data driven outcomes.

Hyperreflectivity of the outer portion of the outer nuclear layer seen on optical coherence tomography in some cases of NR2E3‐associated retinopathy

Aims/Purpose: Bi‐allelic variants in NR2E3 are associated with Enhanced S‐cone Syndrome. Several features have been described on optical coherence tomography (OCT) including schisis, outer nuclear layer (ONL) thickening and ellipsoid zone thickening in some patients. We have observed that in some individuals, the outer portion of the ONL appears hyperreflective compared with the inner portion. We investigated the prevalence of this sign in our genetically confirmed patient cohort.Methods: The electronic genetic database of Moorfields Eye Hospital was searched for patients with molecularly confirmed autosomal recessive NR2E3‐retinopathy. Patients who had undergone macular OCT (Spectralis, Heidelberg Engineering) were included. The horizontal foveal scan from the right eye (at the first visit for which OCT was available) was examined. The presence or absence of the specific sign was noted, together with presence of other features including schisis, atrophy or scarring.Results: 33 patients from 29 unrelated families were included (mean (SD) age, 29 (17) years; range from 5 to 59 years). Of these, 7 (21%) showed some hyperreflectivity in the outer ONL. The mean (SD) age of these individuals was 18 (12) years. The mean (SD) age of the rest of the cohort was 32 (17) years. The difference was not quite statistically significant (p = 0.052). After exclusion of those with schisis, atrophy or scarring (n = 14), the proportion with the hyperreflectivity sign was 37% (7 of 19 patients). The difference in ages reached significance (p = 0.024).Conclusions: A significant proportion of patients (21–37%) with autosomal recessive NR2E3‐retinopathy show this sign. One limitation of this study is that the prominence of the sign is dependent upon the type of scan performed (more distinct on single line scans with greater averaging than on regular volume scans). Patients with the sign were younger on average, suggesting it may be more prevalent in earlier stages.

Subfoveal and Parafoveal Choroidal Thickening in Patients with Keratoconus Using the ETDRS Grid on Swept-Source OCT.

There is growing evidence that confirms morphological changes in the posterior structures in patients with keratoconus (KC); however, isolated alterations could have been missed. This study assesses choroidal thickness (CT) in the fovea and beyond in KC eyes. This prospective case-control and non-randomized study enrolled 107 eyes, 62 eyes of 62 patients with KC, and 45 age-matched eyes of 45 control subjects with axial length in the range of 22-26mm. Swept-source optical coherence tomography (SS-OCT) was performed to manually measure the subfoveal choroidal thickness (SCT) using a single-line scan. CT was obtained automatically from the Early Treatment Diabetic Retinopathy Study (ETDRS) grid using the 12-lines radial scan pattern. A two-way repeated-measures analysis of variance (ANOVA) was conducted to evaluate CT variations among macular eccentricity, parafoveal area, and the interaction between both factors. CT was compared in all parafoveal areas between groups and subgroups of KC. SCT was significantly thicker in KC eyes (357 ± 57µm) than in healthy eyes (325 ± 63µm) (p < 0.001). Significant choroidal thickening was observed in the central ring and outer and inner rings of the temporal, superior, and inferior parafoveal macular areas (p < 0.001), except in the outer ring of the nasal macular zone (p > 0.05) of KC compared to healthy eyes. The CT significantly decreased from the center to the outer ring regardless of the presence of KC (p < 0.001). The choroid in the nasal macular zone was significantly thinner than that in the temporal, superior, and inferior parafoveal areas (p < 0.001). The choroidal structure increased its thickness not only in the subfoveal area, but also in eight parafoveal areas of the ETDRS grid encompassing a wider area of macular examination. These findings demonstrate and corroborate that keratoconus is not a purely corneal disease. Furthermore, it confirms the role that the choroidal structure has in the pathophysiology of keratoconus.

Reactor design via scan line patterning: An implicit approach to create scalable microstructured parts in selective laser melting

The adaptation of additive manufacturing for chemical flow reactors has recently gained momentum as the methods become more advanced and equipment is increasingly affordable. With the design of periodic open cellular structures (POCS) from metal selective laser melting (SLM), structured catalyst substrates can be realized in a much more ordered fashion than well-established metal foams with a random structure. Hence, tailored transport properties are achieved and flow profiles are homogenized, eliminating flow channeling and stagnant flow zones.However, with current SLM methods, the minimal achievable feature size and therewith the specific surface area is still limited. Moreover, the size of finely resolved STL files that define the structure grows exponentially with decreasing feature sizes, further limiting the scalability of methods with direct structure definition.In this work, we present a method for implicit structure design by metal SLM with specific surface areas and porosities that compete with established catalyst substrates. The definition of the microstructure is realized by control of the laser scan lines, where single scan lines create fine struts. The general applicability of our method to various metal materials is demonstrated by production from stainless steel and copper. In a numerical study for a model steam reforming application, we show that the POCS provide mass transfer coefficients and volumetric reaction rates that compete with benchmark substrates.Scan line patterning therefore provides a promising method to create highly ordered, well-scalable substrates for heterogeneous catalysis from a wide range of materials, e.g., for the application in highly efficient small-scale reactors.

EFFECT OF LOW-POWER LASER IRRADIATION ON THE SHEAR BOND STRENGTH AND THERMAL CHANGES ACROSS DIFFERENT ZIRCONIA THICKNESSES USING DIFFERENT IRRADIATION TIMES.

To investigate the effect of irradiation time and zirconia thickness using low power Er,Cr:YSGG laser irradia)on (for debonding purposes) on the thermal changes and shear bond strength (SBS) of resin-bonded 3% mol yIrium oxide stabilized tetragonal zirconia polycrystal (3YTZP) specimens. 3Y-TZP slices of 0.5-, 2-, and 3- mm thick were used. The temperatures during laser irradiation using single spot irradiation at different times (30 seconds, 60 seconds, 90 seconds, and 120 seconds) and line scanning irradiation from one spot to another at three different distances (2, 4, and 6 mm) were recorded. Single spot and line scanning irradiation data were analyzed using three-way ANOVA (α &#61; .05) and generalized linear mixed model, respectively. Nonirradiated (control) and irradiated resin-bonded 3Y-TZP specimens were shear tested, and the data were analyzed using two-way ANOVA (α &#61; .05). Under single spot irradiation, the laser-induced temperature was higher through thin 3Y-TZP at any time compared to thick 3Y-TZP. For the line scanning method, short distances (2 and 4 mm) resulted in a significant increase in temperature for 0.5-mm thick specimens. Laser irradiation significantly decreased the SBS of the 0.5-mm group compared to the nonirradiated group. After irradiation, the bond strength of the 2- and 3-mm thick 3Y-TZP was similar to the nonirradiated group. The temperature and bond strength of low-power laser irradiated 3Y-TZP specimens was affected by the specimen thickness but not by the irradiation time tested. Low-power laser irradiation is an effective debonding method for thin Y-TZP restorations.

Research on applying scan matching algorithm to improve velocity measurement accuracy of single-line ranging lidar

There has been increased demand for safe and efficient speed measurement of moving objects in engineering and practical applications, particularly in scenarios involving the measurement of the movement speed of objects at close range. Thus, this study designed a single-line scanning pulsed lidar system. In addition, algorithms were employed to enhance the measurement accuracy of the single-line ranging pulsed lidar. In this study, the lidar was installed on a guideway-integrated testing platform to obtain point cloud data, which was processed using the normal distributions transform (NDT), iterative closest points (ICP), and correlative scan matching (CSM) algorithms. The experimental results demonstrated that the NDT algorithm outperformed the ICP and CSM algorithms in terms of velocity measurement accuracy and algorithm robustness. Moreover, the velocity measurement results obtained from the NDT algorithm were closer to the actual track speed, with a maximum velocity deviation of lesser than 0.021 m/s compared to the actual guideway speed.

Mesoscale Modeling of Extrusion and Solidification During Material Extrusion Additive Manufacturing

In this work, we apply a multiphysics approach to fused deposition modeling to simulate extrusion and solidification. Restricting the work to a single line scan, we focus on the application of polylactic acid. In addition to heat, momentum and mass transfer, the solid/liquid/vapor interface is simulated using a front-tracking, level-set method. The results focus on the evolving temperature, viscosity, and volume fraction and are cast within a set of parametric studies, to include the printing and extrusion speed, as well as the extrusion temperature. Among other findings, it was observed that fused deposition modeling can be effectively modeled using a front-tracking method (i.e. the level set method) in concert with a temperature dependent porosity function. The use of the level-set method for discriminating the phase change interface in this context is relatively new and offers considerable advantages over existing methods.

Automated Multi-NDT Method

This paper deals with the operating principle of a multi-NDT test bench aimed at automatically test wind turbine blade sections. This bench uses two NDT methods, infrared thermography (IRT) which is a global method and phased array ultrasonic testing (UTPA) which is a volumic method. The interest of using UTPA compared to conventional ultrasonic testing (UT) is to cover a larger area for a single scan line. This allows shorter scan durations. Concerning the test course, the IRT method aims first to detect suspicious areas and UTPA comes next for sanctioning the indications previously detected. Thus, the test cycle is shorter than a classic robotized UTPA scan and offers more precision in sizing defects than only an IRT method. This project is a follow-up to tests carried out manually in 2019 at CETIM.

Comparison of the morphological characteristics of the choroidal sublayer between idiopathic macular holes and epiretinal membranes with automatic analysis

PurposeTo compare the choroidal sublayer morphologic features between idiopathic macular hole (IMH) and idiopathic epiretinal membrane (iERM) on spectral-domain optical coherent tomography (SD-OCT) using an automatic segmentation model.MethodsThirty-three patients with idiopathic IMHs and 44 with iERMs who underwent vitrectomies were involved. The enhanced depth imaging mode of SD-OCT was used to obtain the B-scan image after single line scanning of the macular fovea. The choroidal sublayer automatic analysis model divides the choroidal into the choroidal large vessel layer, the middle vessel layer and the small vessel layer (LVCL, MVCL and SVCL, respectively) and calculates the choroidal thickness (overall, LVCL, MVCL and SVCL) and vascular index (overall, LVCL, MVCL and SVCL). The morphological characteristics of the choroidal sublayer in the ERM eyes and the IMH eyes were compared.ResultsThe mean choroidal thickness in the macular centre of the IMH eyes was significantly thinner than that of the ERM eyes (206.35 ± 81.72 vs. 273.33 ± 82.31 μm; P < 0.001). The analysis of the choroidal sublayer showed that the MVCL and SVCL macular centres and 0.5–1.5 mm of the nasal and temporal macula were significantly thinner in the IMH eyes than in the ERM eyes (P < 0.05), and there was a difference in the macular centre of the LVCL between the two groups (P < 0.05). In contrast, the choroidal vascular index of the macular centre in the IMH eyes was significantly higher than that in iERM eyes (0.2480 ± 0.0536 vs. 0.2120 ± 0.0616; P < 0.05). There was no significant difference in the CVI of other parts of the macula, the LVCL or MVCL between the two groups.ConclusionThe choroidal thickness of the IMH eyes was significantly thinner than that of the iERM eyes, which was mainly observed in 3 mm of the macular centre and the MVCL and SVCL layers of the choroid. The choroidal vascular index of the IMH eyes was higher than that of the iERM eyes. These findings suggest that the choroid may be involved in the pathogenesis of IMH and iERM.

Crack growth analysis of ultraviolet nanosecond laser scanning glass with acoustic emission

Undesirable crossing crack defects are prone to occur in the laser processing of glass, but a comprehensive analysis of the crack mechanism is absent. We apply an acoustic emission (AE) monitoring technique in the glass’s laser scanning to reveal the crack phenomenon. A two-step experiment (single-line and multi-line scanning) is designed to present the crossing crack’s occurrence and growth, and the corresponding AE signals are collected and analyzed in different domains. The time-domain AE feature (root mean square) correlates strongly with the laser ablation intensity in the single-line scanning experiment, and the frequency content of 150 ∼ 200 kHz is extracted as the crack characteristic in the multi-line experiment. The crossing crack growth is proved to be generated by the rapid release of thermal stress in the overlapped heat-affected zone by a brief mechanism discussion. This paper interprets the crack behavior in glass’s laser scanning and provides a basis for other monitoring research on laser processing.

Dynamic attitude measurement taken by monocular line scan vision.

Attitude measurements are important parameters for condition monitoring of precision machines. We develop an angle measurement method based on monocular line scan vision to dynamically measure the attitude of shafts. The proposed measurement system, which consists of a single line scan camera, a parallel laser light source, and a triangular mirror, does not require fixation of a sensor on the shaft. The measurement system uses the line scan camera to capture the projection of the shaft. The light source is diffused by a cylindrical lens to yield parallel directional light. Then the parallel directional light is reflected by a fixed-angle mirror and projected onto the projection plane. The captured image can be considered a discrete time sequence. The attitude measurement principle based on linear monocular vision is derived. A double light-spot centroid algorithm is developed to obtain the centroid coordinates of the projection points. The proposed method is investigated by a simulation and experiment. The proposed method can also monitor the vibration of the shaft. The experimental results prove that the proposed method is effective and highly accurate.

High-speed atomic force microscopy for dynamic single molecule structural biology.

High-speed atomic force microscopy (HS-AFM) is a powerful technique that provides dynamic movies of biomolecules at work. We successfully used HS-AFM to take movies and determine dynamic parameters of membrane trafficking systems, transporters and channels. To break current temporal limitations to characterize molecular dynamics using HS-AFM, we developed HS-AFM line scanning (HS-AFM-LS) and HS-AFM height spectroscopy (HS-AFM-HS), methods whereby we scan the HS-AFM tip along a single scan line or keep it at a fixed position, respectively, and detect the motions of the molecules under the tip with sub-nanometer spatial and millisecond to microseconds temporal resolution to characterize single molecule kinetics. To break resolution limitations, we developed Localization AFM (LAFM) by applying localization image reconstruction algorithms to peak positions in high-speed AFM and conventional AFM data and increased the resolution beyond the limits set by the tip radius to reach quasi-atomic resolution on soft protein surfaces in native and dynamic conditions. Here, I will review these recent achievements and present novel data and methods to integrate and strengthen HS-AFM as a powerful tool in structural biology and molecular biophysics. We reason that the progress of AFM must comprise two axes: First, making AFM/HS-AFM a better tool. With the above-mentioned methods, we made significant progress in this axis over the last ∼5 years. Second, making AFM/HS-AFM data an integrated part of the structural biology / molecular biophysics toolbox. To this end, we are developing now methods and data analysis and interpretation methods that interface with cryo-EM and X-ray crystallography, where AFM/HS-AFM can contribute the urgently needed information about structure, dynamics and conformations under close-to-native conditions.

A Calibration Method for the Resolution of 2D TPP Laser Direct Writing.

To improve the fabrication efficiency of the two-photon polymerization (TPP) laser direct writing, the TPP exposure process was set to complete by a single-line scan, which was named 2D TPP. The voxel of the 2D TPP should be large enough to cross the photoresist and the underlayer. To explore the resolution limit of the 2D TPP considering the thickness of the photoresist, a new method named the 45° scanning method was proposed. Meanwhile, a two-photon micro-nano fabrication platform was developed. A group of experiments based on the orthogonal decomposition method was carried out to analyze the width and length of the voxel on the S1805 photoresist under different laser power and processing speed. To confirm whether the resolution of the micro-nano structures fabricated by 2D TPP is consistent with the width of the voxel, aluminum wire grids were fabricated through the 2D TPP and the metal lift-off process. A second-order regression equation of the machining resolution and input parameters of the 2D TPP is deduced. The correlation coefficient between the width of the voxel and the aluminum wire grids is 0.961, which means a significant positive correlation between them. Finally, the second-order regression model derived from the fabrication resolution of the 2D TPP was validated by experiments. Full 2D grids were fabricated using 2D TPP and mental lift-off process. This paper provides a convenient, low-cost, and high-efficiency method for calibrating the fabrication resolution of 2D TPP on various photoresists.

Improvement of Binocular Reconstruction Algorithm for Measuring 3D Pavement Texture Using a Single Laser Line Scanning Constraint

The dense and accurate measurement of 3D texture is helpful in evaluating the pavement function. To form dense mandatory constraints and improve matching accuracy, the traditional binocular reconstruction technology was improved threefold. First, a single moving laser line was introduced to carry out global scanning constraints on the target, which would well overcome the difficulty of installing and recognizing excessive laser lines. Second, four kinds of improved algorithms, namely, disparity replacement, superposition synthesis, subregion segmentation, and subregion segmentation centroid enhancement, were established based on different constraint mechanism. Last, the improved binocular reconstruction test device was developed to realize the dual functions of 3D texture measurement and precision self-evaluation. Results show that compared with traditional algorithms, the introduction of a single laser line scanning constraint is helpful in improving the measurement's accuracy. Among various improved algorithms, the improvement effect of the subregion segmentation centroid enhancement method is the best. It has a good effect on both overall measurement and single point measurement, which can be considered to be used in pavement function evaluation.

Gold nanoparticles coated LIPSS on GaAs for trace detection of RDX and Tetryl

Femtosecond laser-induced periodic surface structures (LIPSS) on GaAs were accomplished using ablation in the air by varying the input pulse energy (5–100 μJ). A single laser scan line was drawn at each energy, and sub-wavelength LIPSS were observed within each line. Their morphology was thoroughly analysed, and their formation mechanisms were discussed with appropriate theoretical support (SIPE-Drude model). These GaAs-LIPSS have good quality over large ablation areas, and the periodicity (663±16 nm) was nearly the same for all energies. Further, a set of GaAs-LIPSS was produced within an area of 2 × 2 mm2 utilizing an optimized energy of 5 μJ. Photoluminescence and Raman studies were performed to understand the laser-induced damage on these structures. Subsequently, these samples were coated with a 25 nm Au layer and annealed at 400 °C in ambience. The resulting plasmonic Au nanoparticles decorated GaAs-LIPSS were used as SERS substrates for detecting dye (MB) and explosive (RDX, Tetryl) molecules. Enhancement factors of ∼105 and ∼104 (lowest detected concentrations of 10−9 M and 10−5 M) were recorded for dye and explosive molecules, respectively. We believe that these results will aid in further developing GaAs-LIPSS with smaller feature sizes for improved sensing and optoelectronic applications.