Non-diffraction-length Bessel-beam femtosecond laser drilling of high-aspect-ratio microholes in PMMA

Bessel beam femtosecond lasers being non-diffractive are well-suited for drilling high aspect ratio microholes with minor thermal impact. Hereby, the Bessel beams with different non-diffraction lengths using axicon lenses were generated with different taper angles for analyzing the drilled microholes to optimize the aspect ratio. The experimental results show that the depth of microhole is increasing with the pulse number accumulating for low energy laser pulses. With the increasing of energy laser pulse, the increment of microhole diameter is faster than that of the depth. The large aspect ratio microholes with the maximum value of 348:1 have been formed by Bessel femtosecond laser micromachining.

Automated summary

By using Bessel beam femtosecond lasers for microhole drilling, high aspect ratio microholes can be achieved. Experimental results show that the depth of microhole increases with the accumulation of pulses for low energy laser pulses, while the diameter increases faster with increasing energy laser pulses. Large aspect ratio microholes with a maximum value of 348:1 have been formed using Bessel femtosecond laser micromachining.