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[Display omitted] • Laser irradiation realizes ultra-thin localized Au Coating. • Laser irradiation increases the electrodeposition efficiency. • Laser irradiation improves the surface quality of Au coating. • Laser irradiation achieves precise regulation of dimensional accuracy. • Laser irradiation improves corrosion resistance of Au coating. Traditional electrodeposition requires auxiliary technologies such as mask to realize localized deposited layer. In this paper, ultra-thin Au coating can be obtained selectively by laser-induced electrodeposition without mask, which has advantages in dimensional accuracy, brightness, good compactness. The deposition rate, dimensional accuracy, density, roughness, and corrosion resistance were evaluated under different laser single pulse energy (4.5, 5, 5.5, 6, 6.5, 7, 7.5, and 8 μJ). Furthermore, the spatial distribution of the transient temperature field and the change law of the cathode substrate current under laser irradiation were detected to explore the mechanism induced by laser thermal effect. The results show that laser irradiation can increase the cathode limit current density to reach the Au precipitation potential. Besides, the electrodeposition rate increases with the increase of laser single pulse energy. When the laser single pulse energy is 6 µJ, the electrodeposition rate reaches 0.167 mg/min. Meanwhile, the electrodeposition accuracy and surface density are better, and surface roughness (Sa) is 0.98 μm. Moreover, compared with the Au coating product provided by an electroplating enterprise, the coating prepared by laser-induced electrodeposition has better corrosion resistance. When the laser single pulse energy is 6 µJ, self-corrosion potential (φ corr) is −0.3059 V, and self-corrosion current density (j corr) is 5.066 × 10−5 A/cm2. [ABSTRACT FROM AUTHOR]

[Display omitted] • Laser irradiation realizes maskless localized electrodeposition. • Laser irradiation increases the limiting current density. • Laser irradiation improves the surface quality of Ni-P coating. • Laser irradiation increases the amorphous degree of Ni-P coating. • Laser irradiation improves corrosion resistance of Ni-P coating. To obtain electrodeposited layers with different patterns, the additional auxiliary measures such as mask prepared by photoresist are usually required for traditional electrodeposition (ECD) technology, which may reduce the flexibility and convenience of this method. Meanwhile, the ultrashort pulsed laser can be introduced into ECD process and increase current density in the selected area on cathode, and has potential in helping achieve maskless localized ECD. In this paper, the picosecond (ps) laser-assisted ECD (LECD) method is studied, in which a cyclic laser scanning scheme is used to produce different electrodeposited layers on the cathode substrate. In addition, the realizing mechanism of localized ECD is discussed, and the surface quality of Ni-P coating prepared by LECD is evaluated. The results show that the electrodeposited layers with different sizes (1 × 1 mm, 2 × 2 mm and 3 × 3 mm) can be obtained by laser selective irradiation on the copper substrate (10 × 10 mm), demonstrating that the critical current can be increased to reach the reaction conditions in the irradiated zone by the laser-caused thermal effects. Analysis also shows that the theoretical diameter of zigzag edge can be calculated, which is consistent with that of actual electrodeposited layer, indicating that the precision and localization of electrodeposited layer is controllable by adjusting laser processing parameters. Furthermore, measurement shows that a surface roughness of 0.012 μm and better surface flatness can be obtained by LECD under a pulse energy of 16 μJ, and the amorphous degree Ni-P can be increased by the thermal and photoelectric effects of ps laser irradiation. Besides, the corrosion potential and current density are −0.19 V and 3.83 × 10−6 A/cm2, respectively, and the AC impedance spectrum also indicates a higher electron transfer resistance, illustrating better corrosion resistance can be achieved by LECD (16 μJ). [ABSTRACT FROM AUTHOR]

[Display omitted] • Laser enhances Si electrical conductivity via thermal and photoconductive effects. • Simulation is conducted to quantitatively predict electrical conductivity rise. • Micro-wire, regional coating and complex pattern have been achieved on Si surface. • In-depth analysis of the electrodeposition mechanism is provided. The simulation and experimental study of laser-induced localized and maskless electrodeposition of micro-copper (Cu) structures on p-type silicon (Si) surface is investigated. Firstly, calculations of the internal temperature field and free electron density distribution within Si under nanosecond laser irradiation were carried out, to demonstrate the selective enhancing effect of laser irradiation on electrical conductivity via the thermal and photoconductive manner. Secondly, experimental tests of the laser-induced electrodeposition of micro-wires, regional coatings and complicated patterns on Si surface without mask were performed successively, to illustrate the effectiveness of the proposed method. The experimental results indicate that laser pulse width and scanning space significantly affect the quality of the deposited layer. Specifically, dense and flat micro wires can be achieved when the laser pulse width is 100 ns, which is associated with a width of about 71.7 μm and thickness of around 10.9 μm. In addition, the laser scanning space should be well optimized to balance the uniformity of the regional coating and the stray deposition near the edge. Finally, the reduction of Cu2+ and deposition of Cu atom at Si surface were discussed, as well as the development of transitional layer, to supply an in-depth analysis of the electrodeposition mechanism. [ABSTRACT FROM AUTHOR]

The benefits of low-power consumption, high throughput and high parallel processing suggest that optical computing has great potential for information processing. In this article, we propose a multifunctional plasmonic waveguide system (MPWS) to implement various optical functions based on metal coding metamaterials and inverse design technology. Due to the flexible and multivariant manipulation of electromagnetic waves with coding metamaterials, the MPWS can be utilized as an ultra-compact multifunctional component in integrated optical processors for optical computing. Because every optical component is designed by a same scheme, the MPWS avoids additional connection loss and waveguide coupling region caused by inconsistent interfaces and footprints. Driven by strong constraint of electromagnetic waves and overcoming the diffraction limit, the size of the core area in MPWS is only 400 nm × 500 nm. To demonstrate the effectiveness of the MPWS, we use it to implement four typical filtering functions and plasmon-induced transparency (PIT)-like effects. Especially, the Q-factor of PIT-like effects reaches to 58.13. Meanwhile, the simulation results optimized by inverse design technology show high consistency with that theoretically calculated by the combination of coupled-mode theory and the transfer-matrix method. Compared to previous works, our proposed MPWS not only provides a universal scheme to implement various optical information processing functions for optical computing but also shows the applications of inverse design on photonic devices. • The metal coding metamaterials are utilized in the MDM waveguide system. • Five optical functions are implemented in the same scheme with a compact footprint. • The inverse design technology greatly improves the performance of photonic devices. • The physical mechanisms behind the optical functions are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Laser remelting can remove surface cracks. • The remelted layer changes from amorphous to crystalline. • There are many pores in the remelted layer due to cracks. • The crack size affects the corrosion resistance of the remelted coating. The amorphous Ni-P coating crack may further propagate with an increase in electrodeposition (ECD) time, and hence decreases the corrosion resistance. In this study, the Ni-P coating was firstly prepared by picosecond (ps) laser-assisted ECD (LECD), followed by a nanosecond (ns) laser remelting step to remove cracks. The corrosion behavior was detailed evaluated under different LECD time and processing sequence. The results show that the ns laser remelting step results in an increase in surface roughness (Sa) by about one order of magnitude, as well as phase transition from amorphous to crystalline. The LECD time length significantly affect the corrosion behavior after the remelting step, as obvious decrease in corrosion resistance compared with the non-melted surface can be observed for 40 min and 90 min LECD. In contrast, for 180 min case, the corrosion behavior has been significant improved. Longer LECD time may reduce the surface corrosion defects on the remelted coating, and hence decrease the probability of solution-defect contact and hence cracks development, thus improving corrosion resistance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Superhydrophobicity is formed on glass with PTFE by laser back ablation. • CA is 153 ± 2°, and RA is less than 2°. • Micro/nano structures were formed by plasma etching glass. Superhydrophobic surfaces are typically prepared by composite processing and coating with low-surface-energy materials. Transparent, hard, and brittle materials (e.g., glass) are typically covered with low-surface-energy coating to form a superhydrophobic surface. In addition, achieving superhydrophobicity generally requires aging or modification to obtain a low surface energy by composite processing. Therefore, the preparation of superhydrophobic surfaces using one-step method is more efficient and economical. In this study, a method of realizing a superhydrophobic structure by laser back-facing direct etching is proposed. A superhydrophobic structure was immediately realized in one step using glass as the substrate and polytetrafluoroethylene (PTFE) as a coating. In addition, the surface morphologies of microstructures were studied for different laser parameters (laser single pulse energy and scanning rate). The results showed that at a laser pulse energy of 12 μJ and scanning rate of 100 mm/s, the contact angle (CA) of the obtained surface structure was 153 ± 2°, and the rolling angle (RA) was less than 2°, implying superhydrophobicity. At a low laser energy (less than 10 μJ) and a scanning rate lower than 80 mm/s, the sample broke during etching. At scanning rates of 100 mm/s and higher, the surface was not superhydrophobic. Further, at high laser energies (more than 12 μJ), the samples disintegrated. Scanning electron microscopy (SEM) showed that micro/nano structures were formed on the surface. The results of the elemental content analysis and X-ray photoelectron spectroscopy (XPS) indicated that the sample surface was attached to fluorine-containing nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: An ultra compact photonic crystal (PC) ring-shaped channel drop filter (RSCDF) is proposed to generate single side band (SSB) signal for 60GHz ROF system. This PC-RSCDF contains a bus waveguide, a resonant cavity, a ring-shaped waveguide (RSW) and a coupled cavity output waveguide. The notch depth and notch bandwidth of CDF can get 98% and 0.4nm respectively by inducing RSW and shifting the center defect rod of cavity and the rod around the cavity. Then, a method of fine tuning the resonant frequency of PC-RSCDF is proposed by adjusting the radius of insensitive rods which have weak coupling interaction with the light and the sensitivity of structure can be decreased, and the resonant frequency can be shifted to the sideband frequency of double side band (DSB) signal accurately. Finally, a 60GHz ROF SSB modulation system is demonstrated by using designed PC-RSCDF that can filter lower or upper sideband by changing its structure parameters. The extinction ratio (ER) of lower and upper sideband can get 20.9dB and 18.6dB respectively. [Copyright &y& Elsevier]

• Temperature-dependent properties of material and coupling strength are employed. • Model is verified by comparing the predicted and measured results. • For low fluence case, TTM is not necessary when the pulse width is over 200 ps. • Under high fluence, material removal and heat diffusion are detailed analyzed. • Groove depth and profile evolve periodically with respect to scanning times. A 2D two-temperature model (TTM) is developed for picosecond laser micro-grooving of copper (Cu) and discretized using the finite difference scheme, to explore the temperature evolution and groove formation process. For lattice and electron subsystems, as well as the coupling strength between them, comprehensive temperature-dependent properties are employed and updated in real time to make the calculation more accurate. The model verification is then conducted and a reasonable good agreement has been found between predicted and measured groove depths. Using the verified model, computational studies of temperature field evolution are carried out in different fluence levels. For low fluence of around 0.283 J/cm2, phase change can be neglected, and the temperature difference between two subsystems decreases with an increase in pulse width and can be neglected when the pulse width is over 200 ps. In contrast, for high fluence of about 10.61 J/cm2, the maximum lattice temperature increases rapidly to boiling point within 3 ps, and the peak electron temperature is around 10 times higher, leading to material removal via evaporation. Under this high fluence level, groove depth around 0.25 μm is obtained within a 12 ps single pulse irradiation. In addition, thermal diffusion occurs from the residual hot zone adjacent to groove edge towards surrounding area during the off-pulse period, as the heat affected zone depth is up to 1 μm after 500 ps and over 4 μm after 6 ns, and the peak residual lattice temperature drops to about 396 K from boiling point within 53 ns. Moreover, the groove depth and groove profile show a periodically evolving manner with respect to scanning times, and for each scanning, a slow-fast-slow pattern has been observed in groove depth increase and profile development. [ABSTRACT FROM AUTHOR]