Femtosecond laser processing is used in a wide range of  modern technology manufacturing. Its significance is particularly evident in sectors that demand high accuracy and minimal heat effects, like microelectronics, biomedical devices, and photonics. The field has recently seen ultraviolet (UV) wavelengths become a standard in laser processing as optical coatings have become resistant to prolonged exposure to UV radiation. These features have opened up exciting new avenues in both manufacturing and scientific research.


In this study, we explore the application of novel femtosecond laser that produces a flat-top intensity distribution, at a wavelength of 254 nm (4^th harmonic of fundamental 1030 nm radiation). The 4^th harmonic offers unique advantages in material processing due to its position in the direct absorption regime for multiple glass and polymer materials. Our experiments demonstrate the effective ablation of soda-lime glass using this specific wavelength.


A key feature of our methodology is the employment of a flat-top intensity distribution in the laser beam. Comparing to the conventional case of the Gaussian intensity distribution, a notable advantage is the consistent size of the damage patterns (craters) in both transverse directions, irrespective of variations in pulse energy or number of pulses impinged. This consistency is not achievable with traditional Gaussian distributions, making this approach more precise and predictable. In addition, the flat-top DUV laser source may be used for the removal of coatings on transparent substrates.