Laser-induced optical breakdown effects of micro-lens arrays and diffractive optical elements on ex vivo porcine skin after 1064 nm picosecond laser irradiation.

The current study aims to investigate the effects of micro-lens arrays (MLA) and diffractive optical elements (DOE) on skin tissue via intra-dermal laser-induced optical breakdown (LIOB) after irradiation of 1064-nm picosecond laser light at high energy settings. Irradiation with MLA and DOE was tested on dimming paper, tissue-mimicking phantom, and dark pigmented porcine skin to quantitatively compare distributions of micro-beams, micro-bubbles, and laser-induced vacuoles in the skin. DOE yielded more uniform distributions of the micro-beams on the paper and laser-induced micro-bubbles in the phantom, compared to MLA. The ex vivo skin test confirmed that the DOE-assisted irradiation accompanied more homogeneous generation of the micro-beams on the tissue surface (deviation of ≤ 3%) and a high density of small laser-induced vacuoles (∼78 µm) in the dermis than the MLA-assisted irradiation (deviation of ∼26% and ∼163 µm). The DOE-assisted picosecond laser irradiation may help to achieve deep and uniformly-generated vacuolization under the basal membrane after intra-dermal LIOB for effective fractional skin treatment.