Large scanning field laser concurrent drilling system with a five-axis independent control for special-shaped holes.

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.

Tunable metasurface for independent controlling radar stealth properties via geometric and propagation phase modulation.

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.

Single-pass cutting of frosted glass via change of laser incident medium.

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.

Extending the 3D scanning range of reflective dynamic focusing device-based laser scanners.

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.

Composite laser beam separation technology for brittle transparent materials.

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.