In this paper, a triple galvanometer laser three-dimensions (3D) scanning system (TGLSS) was proposed. The system consisted of three galvanometers and two parabolic mirrors, with rapid movement of the laser focus in 3D space by rotations of the three galvanometers. The optical principle of the TGLSS was analyzed, and the method of designing TGLSS by geometrical optics and Abbe’s sine condition was given in detail. Scanning range and focusing quality were analyzed by optical simulations. An experiment was carried out to verify the feasibility of TGLSS. The implications of TGLSS for reflective dynamic focusing device (RDFD)-based laser system and their impact on technologically relevant applications were discussed. The great potential for enhancing the speed of advanced laser processing in 3D space was offered by TGLSS.

The tunable and reversible fabrication function of stealth metasurfaces has significant application value in complex electromagnetic environments., but the extremely low fault tolerance of the existing fabrication methods limits their further development and utilization. In this manuscript, a design and fabrication method for rewritable broadband stealth metasurfaces with memory function is proposed. The reversible phase transition is achieved by laser induced germanium telluride (GeTe) film, which provides the possibility for metasurface to realize the rewriting function. The process of laser induced GeTe and the simulation model of GeTe are investigated, and the conclusions are verified by rewritable broadband polarization converter (RBPC) and rewritable broadband lossy absorber (RBLA). The experimental results show that the reflectivity of fabricated RBLA is less than -10 dB in the range of 7.8-16.1 GHz, which is in good agreement with the numerical simulation results. Meanwhile, there is a highly consistent performance effect before and after repeated induction. The research has the advantages of high efficiency, region selectivity, non volatility and high fault tolerance, which can provide new manufacturing ideas and good candidates for tunable metamaterials.

Advanced Optical MaterialsVolume 12, Issue 7 2470022 Inside Front CoverFree Access Tunable Stealth Metasurface via Dual Geometric Phase Modulation (Advanced Optical Materials 7/2024) Hao-Ran Ma, Hao-Ran Ma Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorTian-ting Chen, Tian-ting Chen Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorLe Liu, Le Liu Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorJia-ji Yang, Jia-ji Yang Chengdu Aircraft Industrial (Group) Co., Ltd, Chengdu, 610073 ChinaSearch for more papers by this authorYa-qing Qiao, Ya-qing Qiao Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorShao-rui Yang, Shao-rui Yang Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorYi Liu, Yi Liu Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorJun Duan, Jun Duan Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorWei Xiong, Wei Xiong Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorLei-min Deng, Lei-min Deng Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this author Hao-Ran Ma, Hao-Ran Ma Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorTian-ting Chen, Tian-ting Chen Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorLe Liu, Le Liu Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorJia-ji Yang, Jia-ji Yang Chengdu Aircraft Industrial (Group) Co., Ltd, Chengdu, 610073 ChinaSearch for more papers by this authorYa-qing Qiao, Ya-qing Qiao Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorShao-rui Yang, Shao-rui Yang Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorYi Liu, Yi Liu Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorJun Duan, Jun Duan Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorWei Xiong, Wei Xiong Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this authorLei-min Deng, Lei-min Deng Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074 ChinaSearch for more papers by this author First published: 13 March 2024 https://doi.org/10.1002/adom.202470022AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Graphical Abstract Tunable Stealth Metasurface In article number 2301898, Lei-min Deng and co-workers propose a novel design method for low-reflection metasurface by integrating germanium telluride (GeTe) film. Through the reversible phase transition of GeTe film and polarization conversion performance of coding units, the metasurface can exhibit efficient stealth characteristics in different frequency bands. The phase characteristics of units and the electromagnetic scattering function of the arrays are analyzed in detail. This study provides a good candidate for tunable stealth materials. Volume12, Issue7March 5, 20242470022 RelatedInformation

In the present work, a laser surface desensitization (LSD) method was carried out on sensitized AA5083 alloy with the underlying microstructural evolution examined. The enhanced corrosion resistance after LSD process was confirmed by nitric acid mass loss test (NAMLT), immersion test and electrochemical measurements, which is mainly ascribed to the modification of grain boundary chemistry. Accompanied with the dissolution of grain boundary β (Al3Mg2) phase during LSD process, the grain boundaries could be characterized by Mg segregation or nano-sized Mg-rich clusters, which may also be absent from chemical uniformity depending on grain boundary misorientation.

The tunable and reversible manufacturing function of stealth metamaterials is of great practical significance to adapt to complex electromagnetic environment. However, the low fault tolerance of existing manufacturing methods limits their further development and utilization. In this article, the microstructure evolution and phase transition mechanism of germanium telluride (GeTe) film under different deposition conditions, laser modes, and scanning parameters were investigated. The experimental results show that sputtering pressure and laser pulse width have important effects on the deposition and modulation of GeTe. There are sputtering pressure threshold (SPT) and pulse width threshold (PWT), which determine the crystallization evolution mode and phase transition performance of GeTe film, respectively. For each sputtering pressure and laser pulse width, there are optimal sputtering power and repetition induction times to achieve the best film deposition quality and reverse phase transition function. Finally, the rewritable broadband lossy absorber (RBLA) is fabricated based on laser induction research, which can achieve low reflection stealth function in the range of 8.4-15.7 GHz. After repeated induction, the performance of RBLA remains the same, which is consistent with simulation results. The process and mechanism of GeTe in the fabrication and modulation stage are systematically analyzed and discussed for the first time, which provides a new solution and good candidate for the fabrication and modulation of stealth materials.

The tensile strength of the modified cross-section (MCS) determines to a certain extent whether the composite laser can complete the separation of glass, and the quality and efficiency of the separation. In this work, the effect of the picosecond Bessel laser on the tensile strength of soda-lime glass was systematically investigated for the first time. The relationship between the tensile strength and residual stress was not negatively correlated absolutely. The tensile strength was also related to the homogeneity and micro-structure of MCS, including micro cavities, cracks, and voids. Meanwhile, it was pointed out that by selecting appropriate modified parameters, the plasma shielding effect can be suppressed and the micro-morphology of MCS can be controlled to obtain smaller tensile strength and better cutting quality. Secondly, the stress field distribution at the crack tip was simulated to analyze the mechanism when the continuous wave (CW) laser interacted with the modified glass. The simulation results showed that only the stress perpendicular to the laser incidence direction and the scanning direction exceeded the tensile strength of glass material, ensuring that the cracks propagated only along the MCS. Finally, one-time separation of glass was achieved by using a composite laser beam separation (CLBS) technology with a speed of 50 mm/s, which was comparable to the industrial level, and the roughness of separated sidewall was less than 0.5 μm.

Objective Processing blind holes in FR4 copper- clad boards to interconnect electronic components is an essential method in printing circuit boards. The quality of blind hole manufacturing is a crucial factor in determining device performance. Laser processing offers advantages such as high precision, no mechanical force, and flexible control, making it the primary method for machining blind holes in FR4 copper-clad boards. Recently, the application of ultrashort pulse lasers has reduced the thermal effects and improved drilling accuracy. However, current laser processing techniques still face challenges in controlling the taper of hole sidewalls and achieving sufficient hole depth. Sidewall taper is a crucial indicator for evaluating blind holes. To ensure reliable interlayer connections, the solder pad at the bottom of the blind hole should be exposed as much as possible. On the other hand, blind holes with uniformly inclined and smooth sidewalls are more conducive to subsequent metallization processes, thus improving the yield of finished products. Considering these conflicting requirements, the ratio of the bottom diameter to the top diameter of blind holes must be controlled within the range of 70%. 90%. Furthermore, existing research primarily focuses on shallow blind holes, and the manufacturing of deep blind holes with depths exceeding 500 mu m still presents significant challenges. In this study, we adopt five-axis laser scanning technology to avoid obstruction of the laser beam by the material surface and sidewalls in order to achieve sidewall taper adjustment and improve blind hole depth. Methods In this study, a five-axis laser scanning system with a wavelength of 1030 nm and a pulse width of 436 fs is employed to perform laser scanning. The experimental material is an FR4 copper- clad board, with the glass fiber composite material thickness of 925 mu m and the copper thickness of 35 mu m. The processing of blind holes adopts a layer-by- layer material removal method. The processing of each layer is divided into two steps. In step 1, the laser draws a spiral line on the material surface, and in step 2, the laser performs additional scanning around the hole circumference to increase the material removal rate at the sidewalls. Simultaneously, during the laser scanning of the two- dimensional pattern, the five-axis scanning system controls the tilt angle of the laser beam to avoid obstruction of laser energy by the hole sidewalls. After the scanning is completed for one layer, the laser focus moves downward to process the next layer of material until the blind hole processing is finished. Compressed air at a pressure of 1 bar (1 bar= 105 Pa) is supplied coaxially. The processed results are observed using a laser confocal microscope. Results and Discussions Compared to laser repetition rate and scanning speed, the impact of laser pulse energy on the sidewall taper is more significant ( Fig. 2). Modifying the line spacing of the spiral pattern can enhance the uniformity of material removal at the bottom of the hole and mitigate the influence of material anisotropy on the uniformity of material removal (Fig. 3). By adjusting the scanning strategy, continuous control over the sidewall taper and hole geometry dimensions can be achieved (Figs. 4 and 5). The hole sidewalls are straight with surface roughness (Sa) of less than 5 mu m. The glass fiber composite material at the bottom of the blind hole is thoroughly removed, with a bottom roughness of less than 2 mu m and good roundness. The damage depth to the copper layer at the bottom of the blind hole is less than 1 mu m (Fig. 6). Conclusions This study investigates the femtosecond laser machining technology for deep blind holes in FR4 copper-clad boards using a five-axis laser scanning system. The research demonstrates that, compared with laser repetition rate and scanning speed, the variation in laser pulse energy has the most significant impact on the sidewall taper of blind holes. Matching the line spacing of the scanning pattern with laser processing parameters can improve the uniformity of material removal inside the holes. By adjusting the laser scanning strategy, the sidewall taper of blind holes can be controlled, allowing for continuous and adjustable diameter ratios between the bottom and entrance of the blind hole within the range of 70%. 90%. It also enables the adjustment of the blind hole radius, with a maximum aspect ratio of 4.9:1. Inspection of the drilling results at the bottom of the blind hole reveals complete removal of the glass fiber composite material, with a copper layer damage depth below 1 mu m. This research achieves high- precision manufacturing of deep blind holes in FR4 copper-clad boards and continuous control of sidewall taper, enhancing the quality of blind hole machining and promoting the application and development of five-axis laser scanning technology.

This study investigated the effect of laser angle-of-incidence (AOI) on the sidewall quality of femtosecond laser drilling carbon fiber-reinforced plastic (CFRP). The results indicated that increasing the laser AOI could prevent laser blockage by the sidewall, reducing fiber loss and resin melting and re-solidification. The laser energy density was also raised with a larger laser AOI, which enhanced the laser processing efficiency and reduced the sidewall taper. However, this also led to cavities and crevices caused by the resin loss between the fibers. By adjusting the drilling strategy and the laser energy, the sidewall taper was eliminated, and the resin loss was reduced. This work proposes a novel approach to enhance the sidewall quality of femtosecond laser drilling CFRP, which has implications for the manufacturing and application of CFRP components.

Five-axis laser scanning technology is an effective drilling method for special-shaped holes. Due to a gap in laser angle-of-incidence (AOI) control within a large scanning field, current technologies are challenging for fabricating large-size holes or special-shaped hole arrays. In this paper, a large scanning field five-axis laser concurrent drilling system was proposed. The laser AOI was independently controlled using two pairs of synchronous deflection mirrors. The laser control deviations under a large scanning field were investigated systematically by simulation and experiment. By establishing a complete correction method, the laser AOI control within a scanning field diameter of up to 35 mm was achieved. A series of special-shaped holes were fabricated concurrently on a 3.6 mm thick glass fiber reinforced plastic (GFRP), verifying that the AOI can be controlled by the five-axis laser scanning system. Our work provides a novel method to increase the scanning field of the five-axis laser scanning technology, expanding the application scope of the five-axis laser processing.

Reflective dynamic focusing devices (RDFDs) have shown their potential in laser scanning as high-performance laser Z-direction focusing devices. However, the scanning range of RDFD-based scanners is limited by aberrations during dynamic focusing. An aspheric symmetry correction (ASC) method was proposed to extend the effective scanning range. An aspheric lens was introduced to correct the optical path difference (OPD) and optimize aberrations. As a result, the scanning range in the three-dimensional (3D) space increased by 15.2%. The ASC method has been proven to extend the 3D scanning range of RDFD-based scanners and may have broad application prospects.

We report a water medium-assisted composite laser cutting (WMACLC) technology for what is believed to be the first time to achieve single-pass separation of frosted glass (FG). The water medium was used to flatten the surface of FG to reduce the diffuse reflection and random refraction of the incident laser. The simulation results of picosecond pulsed laser Bessel beam (PPLBB) intensity distribution in FG showed that the peak intensity in the presence of water can reach about 24 times and 2.3 times that in the absence of water when the PPLBB is 0.08 mm and 0.3 mm below the upper surface of FG, respectively. A PPLBB with higher intensity can be formed along the thickness direction to realize the material modification. A coaxial CW laser provides the thermal tensile stress required for separation. Finally, high-quality separation of FG was achieved using the WMACLC technology with a speed of 50 mm/s. No deviation in the separation track and no edge collapse occurred. The roughness Sa of the separated sidewall is less than 0.3 µm.

Metasurfaces have been verified as an ideal way to control electromagnetic waves within an optically thin interface. In this paper, a design method of a tunable metasurface integrated with vanadium dioxide (VO2) is proposed to realize independent control of geometric and propagation phase modulation. The reversible conversion of VO2 between insulator phase and metal phase can be realized by controlling the ambient temperature, which enables the metasurface to be switched quickly between split-ring and double-ring structures. The phase characteristics of 2-bit coding units and the electromagnetic scattering characteristics of arrays composed of different arrangements are analyzed in detail, which confirms the independence of geometric and propagation phase modulation in the tunable metasurface. The experimental results demonstrate that the fabricated regular array and random array samples have different broadband low reflection frequency bands before and after the phase transition of VO2, and the 10 dB reflectivity reduction bands can be switched quickly between C/X and Ku bands, which are in good agreement with the numerical simulation. This method realizes the switching function of metasurface modulation mode by controlling the ambient temperature, which provides a flexible and feasible idea for the design and fabrication of stealth metasurfaces.

By combining a picosecond Bessel laser and a continuous-wave (CW) fiber Gaussian laser with the same optical axis, a composite laser beam separation (CLBS) technology that allows the fast, high-quality separation of brittle transparent materials was developed for the first time, to the best of our knowledge. In this experiment, 1-mm-thick soda lime glass was separated using this CLBS technology, and the CLBS separation mechanism was analyzed. The experimental results show that a separated surface similar to frosted polishing can be obtained by CLBS, and the edge chipping of the separated upper surface was no more than 0.5 µm. The separated sidewall was flat and smooth without separation defects such as cracks or broken edges, and the surface roughness (Ra) was 0.12 µm. The separation speed reached 12 mm/s and can be further improved by increasing the CW laser power density. This research provides a new way for lasers to separate brittle transparent materials.