“…First, undoped silicon wafers were cleaned with acetone, ethanol, and deionized water for 30 min to obtain a clean surface. The femtosecond laser (343 nm, 200 kHz, 280 fs (Light Conversion Pharos, Vilnius, Lithuania)) is tightly focused through a high numerical aperture objective lens (NA = 0.95, 40×) and matched with a three-dimensional piezoelectric platform (the strokes of the xand y-axes are 1.5 mm, that of the z-axis is 100 µm, and accuracy is 1 nm) to realize the preparation of micro/nanostructures on the silicon surface [24][25][26][27][28][29]. In addition, the femtosecond laser can also be used to process other materials via multi-photon absorption, for example, lift off GaN [30,31].…”