Laser Attenuation Research Articles

(Invited, Digital Presentation) Finite Element Analysis of Temperature Distribution on Laser Enhanced Electroless Plating by Continuous Wave Laser

Laser enhanced electroless plating is a technique to deposit metal locally by irradiating a laser beam onto a substrate immersed in a plating solution. Since micro-sized metal deposits can be fabricated, it is expected to be applied to 3D-MID and high-definition metal 3D printers. We have performed Laser enhanced electroless plating of iron substrates in electroless nickel (Ni) plating solution using a continuous-wave (CW) laser and clarified the change in the properties of Ni deposits as a function of laser irradiation time. However, the temperature distribution on the substrate surface, the relationship between temperature change and Ni deposition form, deposition temperature conditions, and deposition mechanism have not been clarified.In this study, to clarify the relationship between the substrate surface temperature and Ni deposition conditions during Laser enhanced electroless plating, we first measured the temperature distribution and temperature change on the backside of the substrate during Laser enhanced electroless plating using a thermal microscope. Next, the temperature distribution on the surface of the substrate was estimated from the measured temperature distribution on the backside of the substrate using finite element analysis, and the Ni deposition conditions were discussed and the analytical model was validated based on the temperature distribution on the surface of the substrate and the properties of Ni deposits. Furthermore, using the validated analytical model, we analyzed the change in the substrate temperature distribution in response to changes in laser output power.A 980 nm CW multimode fiber laser with a laser power of 10-20 W was irradiated for 300 s through a quartz window onto a steel substrate immersed in the plating solution. A medium-high phosphorus electroless Ni-P solution was kept at 24 °C and circulated at a flow rate of 0.3 L/min using a pump. The iron substrate was coated with a black acrylic coating approximately 30 μm thick on the back side for temperature measurement and fixed over a single-crystal germanium window (2 mm thick). A thermal microscope (Apiste FSV-2000, wavelength range: 8-14 μm) was used to measure the temperature of the backside of the substrate during laser irradiation through the germanium. The temperature measured through germanium was corrected for the effects of reflection and attenuation using a coefficient obtained from the temperature measured using a thermocouple.The temperature distribution analysis was performed using finite element analysis software (COMSOL Multiphysics®). The analytical model consists of a 300 µm-thick iron substrate (20 mm diameter), a 30 µm-thick acrylic coating film, and a 2 mm-thick single-crystal germanium, each in contact with the other, without considering the contact thermal resistance at each interface. The surface of the substrate is assumed to dissipate heat to the plating solution, and the backside of the substrate is assumed to dissipate heat to the atmosphere through the coating film and the germanium window, respectively. The heat transfer coefficients were determined as forced convection and natural convection, taking into account the flow rate and velocity, respectively. A heat source with a Gaussian distribution with a spot diameter of 150 μm was placed at the center of the substrate surface. Considering the laser attenuation in the plating solution and the reflection on the substrate surface, the heat quantity was adjusted so that the maximum value of the measured and analyzed temperatures on the backside of the substrate coincided at a laser power of 20W. The adjusted heat value was approximately 10 % of the laser power. Using this analytical model, the temperature distribution on the substrate surface was estimated from the measured temperature on the backside of the substrate when the laser was irradiated at 20 W output power. In addition, the heat quantity at an output of 10-15W was also set to 10 % of the laser power, as in the case of 20W, and the temperature distribution on the backside and surface of the substrate was estimated.The temperature distribution on the surface of the substrate was estimated from the measured temperature distribution on the backside of the substrate using finite element analysis, and compared with the range of Ni precipitation by Laser enhanced electroless plating. The measured and analyzed temperatures were almost identical for the temperature distribution on the backside of the substrate and the temperature variation with irradiation time. Furthermore, from the comparison between the range of Ni deposition and the analytical temperature distribution on the substrate surface, it is estimated that Ni is deposited when the substrate surface temperature is above 80°C. This result is consistent with the Ni deposition conditions of electroless Ni plating in general. Figure 1

Heat transfer and flow of molten pool in single track multi-layer aluminum alloy laser wire additive manufacturing

In the process of single track multi-layer aluminum alloy laser wire additive manufacturing, there is a lack of in-depth understanding of the heat transfer and dynamics within the melt pool, and it is difficult to characterize the flow behavior inside the melt pool. This paper introduces the numerical simulation of single-track multi-layer aluminum alloy laser wire additive manufacturing. Through numerical simulation methods, the continuous feeding of the wire is realized in the form of mass source terms. The results show that as the specific energy K increases, the length and depth of the molten pool gradually increase, the Marangoni force and thermal buoyancy are enhanced, and the flow speed of the molten pool gradually increases. As the number of layers increases, the heat accumulation between layers increases linearly. Finally, the laser attenuation strategy was adopted, and the laser power of each layer was decreased by 100 W. The flow mode in the molten pool transformed from non-rotational to rotational, and the flow velocity of the molten pool was reduced to 0.187 m/s, and the sedimentary layer with excellent geometric morphology was obtained.

Fractal Growth of 2D NbSe2 for Broadband Nonlinear Optical Limiting

AbstractThe compelling demand for laser protection both for civil and defense use calls for new‐generation nonlinear optical materials. Chemical vapor deposition (CVD) techniques provide extra tricks to modulate crystal optical nonlinearity through fractal growth. The synthesized 2D NbSe2 and its fractal structures exhibit giant, broadband laser attenuation behaviors extending into the near Infrared (NIR) range. Particularly, the optical limiting performance generally correlates with the fractal dimension, where Fractal NbSe2 demonstrates enhanced third‐order optical nonlinearity at a huge nonlinear absorption coefficient of 9.7 × 10−4 m W−1 and an ultralow starting threshold of 5 mJ cm−2 at 532 nm. Various techniques include femtosecond spectroscopy, Density functional theory (DFT) calculation and Kelvin probe force microscopy disclose the origin of the strong nonlinearity of the 2D NbSe2 crystals, and suggest the formation of edge states and overall faster carrier dynamics, larger surface contact potential difference NbSe2 fractals contribute to their even augmented nonlinear responses. Fractal engineering thus opens new avenues to fabricate highly efficient laser protection materials, and the blocking of intense beam (a large attenuation factor over 13.3 dB at 532 nm) while allowing transmission of weak one (a high linear optical transmittance over 80%) fulfills the much desired “smart” defense.

Size-dependent optical and dielectric anisotropy of CdS nanowire doped high-birefringent nematic liquid crystalline compound

Highly birefringent liquid crystals have grabbed ample attention because of their potential applications as an active medium for devices in visible, infrared and other spectral regions. Here, we have attempted to study the effect of the size and concentration of CdS nanowires on a nematic liquid crystal. Anisotropy in liquid crystals is one of those distinguishing traits that gain their superiority over other materials. We hereby have analyzed how optical and dielectric anisotropy respond to variations in the size and concentration of the dopant. The study is of significant scientific value because there is very little literature available on how dopant size can alter liquid crystalline properties and also introduces a method to tune the properties of pure liquid crystals (LCs) by varying the size and concentration of the dopant. The study explains how the size of the nanowires changes the analyzed parameters and up to what extent. The obtained results yield a significant increase in both optical and dielectric anisotropy by doping CdS nanowires making them an excellent choice for dopant selection. CdS-doped nematic LC mixtures have proved to be highly birefringent and possess a high positive dielectric anisotropy as well. Such a compound can be of great application in device fabrications such as laser beam steerers, electronic lenses, attenuators and light shutters, etc.

Performance comparison of Duobinary, AMI, CNRZ and CSRZ for next generation FSO communication system

Abstract FSO, known as free-space optics, is a competent technology in wireless communication for providing license free spectrum, bandwidth, and high efficiency in next-generation networks. In this paper, an experimental approach is used to deploy FSO channel communication using different intensity modulation schemes such as CSRZ, chirped NRZ, duobinary and AMI. The performance of FSO link is adversely affected by weather conditions like haze, rain, and fog. By using different techniques, it is possible to overcome the effect of atmospheric turbulences. Therefore, four different modulation formats are compared and analyzed by testing different parameters like laser power, range, attenuation, and data rates. Quality of received signal is judged by taking Q-factor, bit error rate (BER), and eye-diagrams. An operating wavelength of 850 nm has been used to simulate the system designs. This paper aims to conclude the best intensity modulation scheme for its use in next generation networks such as 5G where direct deployment of optical fiber is not possible or feasible.

SRS conversion efficiency assessment of a single cell Raman gas mixture for DIAL ozone lidar.

A single Raman cell configuration useful for DIAL ozone lidar is designed and optimized. The conversion efficiency and flexibility of using a single Raman cell filled with a mixture of high pressure Raman active gases hydrogen (H 2) and methane (C H 4) have been examined and reported. The stimulated Raman scattering (SRS) conversion efficiency of Raman active gases with different total cell pressures and the volume mixing ratio excited with a focused, frequency quadrupled Nd:YAG laser with a maximum pulse energy of 25mJ and a pulse duration of 10ns at 100Hz repetition rate are examined in detail. The gas combination of H 2:C H 4 emits a coaxial beam of two wavelengths, 288.4nm (C H 4) and 299.1nm (H 2), with a maximum total conversion efficiency of about 45%. The optimum volume mixing ratio for generating the required wavelength pair with almost equal energies is found to be 2:1 (H 2:C H 4) at a total cell pressure of 18bar. The contribution of cascade Raman scattering (CRS) and four-wave mixing (FWM) to the higher order Stokes lines is examined. The laser attenuation due to soot formation under various mixing ratios in the cell is also presented.

Investigation of thermal behavior of powder stream and molten pool during laser-based directed energy deposition

Laser-powder interaction and molten pool evolution are two main physical processes in laser-based directed energy deposition (L-DED), which greatly affect the morphology and quality of the deposition layer. In this research, a comprehensive three-dimensional analytical-numerical model which integrates a laser-powder interaction model and material deposition model is developed to study the multi-physics coupling characteristics in L-DED process. The concentration of the powder stream is modeled based on conservation of mass and is in good agreement with the experimental result which is captured by high-speed camera. The effects of main parameters, including laser power, powder feeding rate, powder feeding angle and defocus length on the laser attenuation and the temperature distribution of the in-flight powder particles are analyzed. The results show that the laser attenuation rate increases from 0.72% to 1.36% with the powder feeding angle increasing from 45 deg. to 65 deg-. However, the laser attenuation rate is almost the same with the defocus length of 25 mm, 35 mm and 45 mm. Moreover, the peak powder temperature on the deposition surface increases with the increase of powder feeding angle and decrease of defocus length. Accordingly, the heat and mass input conditions at the molten pool surface for the material deposition model, including powder mass flux, effective laser intensity and powder temperature are obtained from the laser-powder interaction model. The heat transport and fluid dynamics of the molten pool are discussed based on the calculated results from material deposition model. Finally, the calculated molten pool geometry shows good agreement with the experimental results with the relative error <8.5%. This work is helpful in process optimization from the point of view of adjusting the parameters related to the powder stream and deeper understanding of laser-powder interaction and molten pool evolution during the L-DED process.

Random pinhole attenuator for high-power laser beams

Abstract The intensity attenuation of a high-power laser is a frequent task in the measurements of optical science. Laser intensity can be attenuated by inserting an optical element, such as a partial reflector, polarizer or absorption filter. These devices are, however, not always easily applicable, especially in the case of ultra-high-power lasers, because they can alter the characteristics of a laser beam or become easily damaged. In this study, we demonstrated that the intensity of a laser beam could be effectively attenuated using a random pinhole attenuator (RPA), a device with randomly distributed pinholes, without changing the beam properties. With this device, a multi-PW laser beam was successfully attenuated and the focused beam profile was measured without any alterations of its characteristics. In addition, it was confirmed that the temporal profile of a laser pulse, including the spectral phase, was preserved. Consequently, the RPA possesses significant potential for a wide range of applications.

Investigation of partial parity-time symmetry in cesium atomic system

&lt;sec&gt;Parity-time (PT) in atomic systems is of great significance for exploring exotic phenomena in non-Hermitian physics and non-Hermitian systems. It has been found that if PT symmetry is satisfied only in a certain spatial direction, then the Hamiltonian of the system still has a spectrum with eigenvalues of real numbers, which is called partial PT symmetry. In this paper, we use a Λ-type three-level atomic system, which is composed of two ground states &lt;inline-formula&gt;&lt;tex-math id="M6"&gt;\begin{document}$\left| {6{{\mathrm{S}}_{1/2}}, F = 3} \right\rangle $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;,&lt;inline-formula&gt;&lt;tex-math id="M7"&gt;\begin{document}$\left| {6{{\mathrm{P}}_{3/2}}, F' = 4} \right\rangle $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;and an excited state &lt;inline-formula&gt;&lt;tex-math id="M8"&gt;\begin{document}$\left| {6{{\mathrm{P}}_{3/2}}, F' = 4} \right\rangle $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;of cesium atom, to investigate the partial PT symmetry. A probe laser with the detuning of &lt;i&gt;Δ&lt;/i&gt;&lt;sub&gt;3&lt;/sub&gt; = 607 MHz and a coupling laser satisfy the condition of two-photon Raman absorption of cesium atom, forming a loss channel. In order to construct the gain channel, we add the repumping laser that resonates during the transition of &lt;inline-formula&gt;&lt;tex-math id="M9"&gt;\begin{document}$\left| {6{{\mathrm{S}}_{1/2}}, F = 3} \right\rangle $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;to &lt;inline-formula&gt;&lt;tex-math id="M10"&gt;\begin{document}$\left| {6{{\mathrm{P}}_{3/2}}, F' = 4} \right\rangle $\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;, changing the population of the two ground state energy levels, thus reducing the absorption of the Λ level system and forming the gain channel of the atomic system under certain conditions. In order to obtain the equilibrium condition of the partial PT-symmetric system, firstly, the light spot of the repumping laser in the experiment is covered by the probe laser, and then the repumping laser is moved to overlap with half of the probe laser of the detection light. When the gain and loss are balanced, the partial PT-symmetric system is in equilibrium.&lt;/sec&gt;&lt;sec&gt;By changing the beam-waist ratio &lt;i&gt;σ&lt;/i&gt; of the coupling laser to the probe laser, the transition from symmetry to broken phase is observed in partial PT-symmetric systems. By measuring the asymmetry of the detection-beam intensity distribution &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;asym&lt;/sub&gt;, we can accurately determine the partial PT symmetry breaking point, and the breaking point is located at &lt;inline-formula&gt;&lt;tex-math id="M11"&gt;\begin{document}$\sigma = {\sigma _{{\mathrm{cr}}}} \approx 3.8$\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;. The theoretical calculations are in good agreement with the experimental measurements. The results of partial PT symmetry and its phase transition, reported in this study, open up a way to actively manipulate multidimensional laser beams in non-Hermitian systems and have potential applications in the design of optical devices for laser amplification and attenuation in different parts of the laser.&lt;/sec&gt;

Multi-line OH-LIF for gas-phase temperature and concentration imaging in the SpraySyn burner

Gas-phase temperature and OH concentration images are measured in the SpraySyn nanoparticle-synthesis standard burner using multi-line OH laser-induced fluorescence (LIF) thermometry. In this burner, a spray flame fed by a combustible nanoparticle precursor solution is stabilized by a surrounding axisymmetric lean premixed laminar methane/oxygen pilot flame. For measuring OH rotational temperature, the laser is scanned across the 282.05–282.17 nm range and LIF excitation spectra are fitted for each image pixel by simulated spectra. Temperature maps are determined for the pilot flame and the ethanol spray flame with variable dispersion gas flow rates of oxygen used in the two-fluid nozzle. The addition of 2-EHA (2-ethylhexanoic acid) to the solution was found to increase the flame temperature. Laser attenuation across the flame was measured using simultaneous recordings of the fluorescence of uranine/water solution from two dye cuvettes illuminated with the laser sheet before and after the flame and the effect of attenuation was quantified. Absolute OH concentration distributions are determined by combining the LIF images, laser attenuation measurements, and derived temperature distributions. The temporal stability of the flame is investigated for various operating conditions by statistical evaluation of recorded instantaneous OH-LIF images.

Weak non-line-of-sight target echoes extraction without accumulation.

Non-line-of-sight (NLOS) technology has been rapidly developed in recent years, allowing us to visualize or localize hidden objects by analyzing the returned photons, which is expected to be applied to autonomous driving, field rescue, etc. Due to the laser attenuation and multiple reflections, it is inevitable for future applications to separate the returned extremely weak signal from noise. However, current methods find signals by direct accumulation, causing noise to be accumulated simultaneously and inability of extracting weak targets. Herein, we explore two denoising methods without accumulation to detect the weak target echoes, relying on the temporal correlation feature. In one aspect, we propose a dual-detector method based on software operations to improve the detection ability for weak signals. In the other aspect, we introduce the pipeline method for NLOS target tracking in sequential histograms. Ultimately, we experimentally demonstrated these two methods and extracted the motion trajectory of the hidden object. The results may be useful for practical applications in the future.

Influences of laser heating parameters on thermophoretic enrichment of nanoparticles

Thermophoretic enrichment of particles has been recognised as an efficient way to concentrate nanovesicles in biomedical studies. Although some experimental and analytical studies have been undertaken to examine the thermophoretic accumulation mechanisms, few studies have been conducted to optimise the device design. This paper presents a detailed parametric study of a thermophoretic enrichment system, which sandwiches a microchamber containing particle/fluid mixture by a glass top, from where an infrared laser heat source is introduced, and a sapphire bottom, which has a high heat conductivity to prevent overheating. The influences of the laser spot radius, laser attenuation rate, nanoparticle size and laser power are investigated. The radius of the nanoparticle accumulation zone is found to be approximately 1.25 times the laser spot radius. A reduction in the laser attenuation length leads to a reduction of the time taken by the nanoparticles to reach the steady state, but an enlarged zone over which nanoparticles are concentrated. There exists an optimum range of the attenuation length, depending on the required size of the target area. We have also determined the threshold particle size, which decides whether the particle motion is convection-dominated or thermophoresis-dominated. Furthermore, an increase in the laser power reduces the accumulation time. These findings provide guidelines for the design of enrichment systems.

Influence of the laser-induced plume on welding behavior in keyhole welding for stainless steel using a 16 kW disk laser

The spatter is one of the defect factors for laser welding. For high-quality laser welding, the elucidation of the spatter reduction mechanism is required. In our previous study, it was elucidated that the molten pool and keyhole fluctuation contribute to spatter generation from the observation of the keyhole and molten pool under different ambient pressure conditions. However, the main cause of the instability of the molten pool and keyhole has not been clarified. It is considered that the interaction between the laser and plume might cause these instabilities. Therefore, in this study, we focused on the plume generated by laser irradiation. The dynamics of the plume during laser welding and the attenuation of the laser were observed under different ambient pressures. According to these observations, the effect of the plume on instability in laser welding was elucidated. The SS304 was fixed in the vacuum chamber, and the disk laser with an output power of 6 kW swept on the sample to form the weld bead. At the same time, the plume behavior was observed by the Schlieren method, and the attenuation of the laser was measured using a probe laser. As a result, the metal vapor jet, which is a periodical plume ejection, was observed. The attenuation of the probe laser increased with increasing atmospheric pressure. These results suggest that the frequent generation of the metal vapor jet under atmospheric pressure caused instability in the heat input of the laser, which caused instability in the keyhole and molten pool.

Optimization of signal‐to‐noise ratio of laser heterodyne radiometer

AbstractThe ground‐based laser heterodyne radiometer (LHR), which exhibits the advantages of small size, high spectral resolution, and easy integration, has been used for the remote sensing detection of several gases to meet a wide range of needs. This study aims to optimize the laser heterodyne system for detecting CO2 gas by focusing on existing research. Firstly, using the all‐fiber laser heterodyne detection system built by our research group, the power spectrum associated with the radio frequency signals of the detection system is discussed under different conditions: under no irradiation, under sunlight only, under sunlight and laser irradiation at the absorption peak, and under a filter in the spectrum range of 185–270 MHz. Signal‐to‐noise ratios (SNRs) of the high‐resolution spectrum have been obtained using different filter bands of 185–270, 225–270, and 225–400 MHz. Finally, the filter in the 225–270 MHz band, which has the highest SNR, is selected. Consequently, the resolution is improved and the system is further optimized. Furthermore, an optical fiber attenuator is used to change the power of the local oscillator light entering the system, and hyperspectral spectra with varying percentages of input energy and total energy are obtained. When the laser attenuation reaches 40%, the optimal SNR of the system is 486 and can be further improved to meet the expected requirements. This study will provide insights for improving the applicability of laser heterodyne technology in atmospheric sounding.

The Detection Capability of Laser Fuze in Fog, Mist, and Haze Using Monte Carlo Simulations

When choosing a laser wavelength for proximity fuze with high accuracy requirements, the weather condition is a considerable element. Hence, the paper developed a laser detection model in different conditions based on the Monte Carlo method to evaluate the detection capability. As the atmospheric attenuation is a function of the wavelength, there is a conception that the laser pulsed fuze with 1550 nm light suffers from less atmospheric attenuation than 785 or 850 nm laser in all weather conditions (Pratt, 1969). However, in foggy weather (visibility &lt;500 m), the results showed that laser attenuation appeared to be wavelength independent, i.e. the wavelengths of 785 nm, 850 nm, and 1550 nm are equally all attenuated equally by fog. Furthermore, the simulations also allowed the prediction of transmission, as well as the effects of energy scattering and absorption. This paper can provide guidance and reference for the application of laser wavelengths in the laser fuze.

Laser Attenuation and Ranging Correction in the Coal Dust Environment Based on Mie Theory and Phase Ranging Principle

The inadequate ventilation and complex environments in underground coal mines lead to a high concentration of dust particles. As a result, the health of the miners and the accuracy of laser rangefinder measurements are endangered. It is crucial to enhance the laser rangefinder’s efficiency to mitigate health risks and reduce labor intensity. In this study, we propose a laser power attenuation model and a ranging correction model to address the issues of laser power attenuation and inaccurate ranging in coal dust environments. The proposed models are based on theoretical analysis and practical experiments, and both are dependent on the dust particle size (&lt;250 μm) and mass concentration. Firstly, we assessed the factors that caused laser power attenuation and demonstrated that our proposed model could accurately predict them (maximum residual of 0.06). Secondly, we obtained the connection between the attenuation coefficient and dust concentration by applying the Lambert–Beer law. Lastly, we established the ranging correction model by collecting laser wavelength information. The outcomes show that the root mean square error of the corrected values ranges between 0.27 and 0.47 mm. To summarize, our suggested model and correction technique can efficiently enhance the precision of laser rangefinder measurements, thus improving underground work in coal mines.

Development and measurement of airborne oxygen sensor for aircraft inerting system based on TDLAS with pressure compensation and 2f/1f normalized method

Using Tunable Diode Laser Absorption Spectroscopy (TDLAS）technology to accurately measure the oxygen concentration in the ullage of the aircraft fuel tank is of great significance to ensure the safety of the aircraft and improve the working quality of the aircraft onboard inerting system. This paper focuses on designing a smart sensor for the detection of oxygen concentration applied to airborne inerting systems, which can reduce random environmental noise and lineshape errors during the flying process. First, a prototypeincluding a laser emission module with wavelength modulation and temperature control, a multi-reflection long optical path absorption gas cell, and a high-precision signal extraction module are designed. Then, ground experiments at 294 K, and 1 bar are carried out. The oxygen inversion method is designed, the oxygen concentration results are obtained, and the lower detection limit (3.3 ppm) and detection accuracy (9.6 ppm) of the sensor are discussed. Thirdly, the change of absorption line profile influenced by the change of pressure is discussed. The series of oxygen concentration measurement experiments with variable pressure (274 k, 1–0.1 bar) was carried out. and the measurement error is below 1%. Finally, a second harmonic (2f)/first harmonic (1f) normalized method is proposed to eliminate the errors caused by laser attenuation and environmental vibration in oxygen measurement.

The Impact of Ammonium Fluoride on Structural, Absorbance Edge, and the Dielectric Properties of Polyvinyl Alcohol Films: Towards a Novel Analysis of the Optical Refractive Index, and CUT-OFF Laser Filters

The new proton-conducting composite electrolyte films (PCCEFs) consisting of polyvinyl alcohol (PVA) with varying ammonium fluoride salt concentrations were created using an expanded liquid casting process. The X-ray diffraction (XRD) study confirms the composite electrolyte films (CEFs) formation. The improvement in AMF02 salt doping compared to the PVA matrix film approach resulted in decreased variation in the crystalline size values, thus explaining how [NH4+] and polymer PVA matrix films interact. The band gaps decrease when the AMF02 salt filler concentration increases due to increased crystallite size. The suggested composites evaluated successful CUT-OFF laser filters and attenuation, as well as limiting laser power systems. For the 11.11 wt% AMF02 doping salt, the highest DC conductivity was 73.205 × 10−9 (siemens/m) at ambient temperature. Our dielectric results demonstrate that the CEFs are usually suitable for optoelectronic systems. There is a huge need to develop low dielectric permittivity composite electrolyte films (CEFs) for microelectronic devices and the high-frequency region.

Comparison between various dispersion compensation schemes in optical fiber communication system

Abstract Nowadays, the optical fiber communication system has great importance in the communication area. Although the optical fiber communication system has many favorable circumstances, the dispersion was considered one of the main problems. In this paper, the comparison between the design and simulation of different dispersion compensation schemes was displayed. There are different kinds of optical fiber dispersion compensation systems such as fiber Bragg grating (FBG) and dispersion compensation fiber (DCF) are extensively used for optical communication systems. They are usually considered imperative techniques to compensate for the dispersion. The simulation results have been analyzed depending on various parameters by utilizing advanced Opti-System software. The best performance of the system is when the bit error rate (BER) reaches to 1.7 × 10−12 at 1550 nm wavelength and the Q-factor is 6.9 at the 0.000195 eye opening. The modal was simulated using the appropriate parameters which include CW laser wavelength, fiber length (km), and attenuation coefficient (dB/km) at the transmitter side. Three various parameters were tested such as BER, Q factor, and eye-opening.

Simple model for the laser powder interaction during direct metal deposition

In this paper, a simple model is presented for simulating laser and powder interaction during a coaxial laser cladding process, which is a very important part of direct metal deposition. The powder is delivered coaxially with the laser. The idea is to completely melt the powder before it hits the substrate. The laser is being attenuated as it propagates through the cloud of powders. The laser beam that penetrated through the cloud is used to melt the substrate. The track of 3D printing is formed by resolidification as the laser or the substrate scans. The laser attenuation is modeled by the Beer–Lambert law. The heat transfer within each powder is modeled by a lumped capacitance method. We use an enthalpy formulation to easily model and track the melting. The resulting 1D differential equation is solved numerically using Euler's method. The enthalpy and temperature plot is presented. We make use this model to determine the standoff distance. The effects of powder velocity, laser power, powder number density, and powder radius on the standoff distance are investigated and presented.