SiC wafers, due to their hardness and brittleness, suffer from a low feed rate and a high failure rate during the dicing process. In this study, a novel dual laser beam asynchronous dicing method (DBAD) is proposed to improve the cutting quality of SiC wafers, where a pulsed laser is firstly used to introduce several layers of micro-cracks inside the wafer, along the designed dicing line, then a continuous wave (CW) laser is used to generate thermal stress around cracks, and, finally, the wafer is separated. A finite-element (FE) model was applied to analyze the behavior of CW laser heating and the evolution of the thermal stress field. Through experiments, SiC samples, with a thickness of 200 μm, were cut and analyzed, and the effect of the changing of continuous laser power on the DBAD system was also studied. According to the simulation and experiment results, the effectiveness of the DBAD method is certified. There is no more edge breakage because of the absence of the mechanical breaking process compared with traditional stealth dicing. The novel method can be adapted to the cutting of hard-brittle materials. Specifically for materials thinner than 200 μm, the breaking process in the traditional SiC dicing process can be omitted. It is indicated that the dual laser beam asynchronous dicing method has a great engineering potential for future SiC wafer dicing applications.

Flat lens or metalens, as one of the most important application branches of metasurfaces, has recently been attracting significant research interest. Various reflective and transmissive metalenses have been demonstrated in the terathertz, infrared and visible wavelength range. However, metalens operating in the ultraviolet (UV) wavelength range is rare. Moreover, the development of reflective UV metalens, the important counterpart of transmissive ones, falls far behind. In this work, with thorough investigation of material properties, we propose a reflective metalens based on silicon dioxide (SiO₂) and aluminum (Al) that operates in the vacuum ultraviolet (VUV) to visible wavelength region. Four reflective metalenses were designed and optimized for wavelengths of 193, 441, 532 and 633 nm, and prominent focusing capability was observed, especially for the VUV wavelength of 193 nm. Dispersion characteristics of the metalenses were also studied within ±50 nm of the design wavelength, and negative dispersion was found for all cases. In addition, the SiO₂ + Al platform can be, in principle, extended to the mid-infrared (IR) wavelength range. The reflective VUV metalens proposed in this work is expected to propel miniaturization and integration of UV optics.

The broadband perfect absorption of visible light is of great significance for solar cells and photodetectors. The realization of a two-dimensional broadband perfect absorber in the visible range poses a formidable challenge with regard to improving the integration of optical systems. In this paper, we numerically demonstrate a broadband perfect absorber in the visible range from 400 nm to 700 nm based on metasurface composite structures. Simulation results show that the average absorptance is ~95.7% due to the combination of the intrinsic absorption of the lossy metallic material (Au) and the coupling resonances of the multi-sized resonators. The proposed perfect absorber may find potential applications in photovoltaics and photodetection.

Silicon carbide (SiC), due to its characteristic materials performance, gets more attention in Radio Frequecy (RC) and High-power device fabrication. However, SiC wafer dicing has been a tricky task because of the high hardness and brittleness. The blade dicing suffers from poor efficiency and debris contaminants. Furthermore, the laser ablation dicing and Thermal Laser Separation (TSL) can have thermal damage and irregular crack propagation. In this study, Stealth Dicing (SD) with nanosecond pulse laser method was applied to 4H-SiC wafer. A series of experiments were conducted to analyze the influences of different parameters on cross section and surface. An edge defect less than 3 μm and cross section with roughness of about 0.8 μm was achieved. And the three-point stress test was applied to obtain the die strength. Besides, a novel method of double pulse inducing cracks growth was proposed for the first time to optimize the surface edge. Finite Element Analysis (FEA) verifed the feasibility. Through experiments, the edge defect decreased to less than 2 μm. This work contributes to the wafer Stealth Dicing application for SiC and advance semiconductor materials.

Black silicon is a promising and effective candidate in the field of photoelectric devices due to the high absorptance and broad-spectrum absorption property. The deposition around the processing area induced by the pressure of SF₆, gravity, and the block of the processing chamber interferes the adjacent laser ablation and hampers uniform large-scale black silicon fabrication. To solve the problem, femtosecond laser- induced black silicon assisted with laser plasma shockwave cleaning is creatively proposed in our study. The results showed that higher, denser, and more uniform microstructures can be obtained than the conventional laser-induced method without laser cleaning. The average absorptance is 99.15% in the wavelength range of 0.3–2.5 µm, while it is more than 90% in the range of 2.5–20 µm. In addition, the scanning pitch dependence of surface morphology is discussed, and the better result is obtained in the range of 25–35 µm with 40-µm laser spot. Finally, a large-scale 50-mm × 50-mm black silicon with uniform microstructures was prepared by our method. It has been demonstrated that the deposition is effectively eliminated via our method, and the optical absorption is also enhanced significantly. It is of great significance for realizing large-scale preparation of photoelectric devices based on black silicon and lays the foundation for the development of laser-inducing equipment and industrial application.

Black silicon, which is an attractive material due to its optical properties, is prepared mainly by laser inducing in an SF₆ atmosphere. Considering the effect of SF₆ gas on the environment and human health, here we propose an efficient, economical, and green approach to process large-scale black silicon. In the wavelength range of 0.3–2.5 µm, the role of air could replace SF₆ gas to texture black silicon by laser inducing with appropriate processing parameters. Then, to extend the working window of its excellent light-trapping status, laser-plasma shockwave cleaning was introduced to eliminate the deposition and improve the structures and morphology. The results revealed that the micro-nano structures became higher, denser, and more uniform with increasing cleaning times and deteriorating cleaning velocity, which compensated for the role of S atoms from the ambient SF₆. Moreover, absorptance above 85% in the wavelength range of 0.3–15 µm was realized using our method. The effect of scanning pitch between adjacent rows on large-scale black silicon was also discussed. Our method realized the ultrahigh absorptance of large-scale black silicon fabricated in air from visible to mid-infrared, which is of significance in the field of optoelectronic devices.