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

Hyeonsoo Kim,Jongman Choi,Hyun Wook Kang,Jewan Kaiser Hwang,Minjung Jung

doi:10.1364/boe.410991

Hyeonsoo Kim, Jongman Choi + Show 3 more

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https://doi.org/10.1364/boe.410991

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Abstract

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.

Highlights

Melasma is a pigmentary disorder that occurs primarily on the face with brown or gray patches
focal depth (FD) = 0 mm means that the incident micro-beams were focused on the target surface whereas FD = 10 mm represents that micro-lens arrays (MLA) and diffractive optical elements (DOE) approached the surface by 10 mm (i.e., 10 mm closer distance) to focus the incident micro-beams below the target surface
Regardless of FD, both MLA and DOE showed that the macro-beam spots became more blotted with increasing H0

Summary

Introduction

Melasma is a pigmentary disorder that occurs primarily on the face with brown or gray patches. Several therapeutic methods have been performed to treat the melasma, including surgical incision, medical drug, radiofrequency, and laser treatment [1]. High power laser application has been adopted as a popular means to treat the melasma by physically fragmenting skin pigments because of non-invasiveness, rapid treatment time, and short wound recovery [4,5]. A number of Q-switched nanosecond laser systems with various wavelengths (532, 755, and 1064 nm) and pulse durations (10∼100 ns) have been developed and clinically examined to maximize the therapeutic outcomes for the melasma treatment [6]. The nanosecond pulse durations are often longer than the thermal relaxation times (10∼ 30 ns) of the melasma pigments, leading to the partial thermal decomposition of the pigments and unfavorable thermal injury to the surrounding skin [7]

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