FEMTOSECOND LASER SCRIBING OF SAPPHIRE AT WAVELENGTH 1040 AND 520 NM

Sapphire cutting is one of the largest markets in laser materials processing. Since sapphire is one of the hardest transparent materials its mechanical and optical properties made it the ideal choice for use in the production of various devices, such as LEDs and transistors, cover glasses of watches and mobile devices. Among existing laser- or diamond-based tools solutions, femtosecond laser scribing appear as a promising technology since this technology has the unique capacity to produce highly localized bulk modification owing to non-linear absorption. Sapphire cutting with solid-state lasers is well known for many years and has become a modern industrial process. However, achievable process speed and cut quality are still limited. The femtosecond laser scribing of sapphire was studied at wavelengths of 1040 and 520 nm, followed by wet etching in HNO3/HF solution to identify emerging defects. The morphology of the laser ablated sapphire surface was evaluated by scanning electron microscopy. It was shown that at the wavelength of 1040nm, the material was effectively removed from the surface; however, cracks on the surface were formed. The use of the second harmonic gave more accurate and deep cuts compared with the main frequency at the same conditions. At the wavelength of 520 nm, the cracks were formed anisotropically inside the volume of the material. Therefore, there is a potential application of the femtosecond laser scribing for the fabrication of sapphire-based devices.

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