Femtosecond pulsed laser ablation of polyimide at oblique angles for medical applications

We report the ablation results for surface modification of polyimide Kapton HN foils using ultrashort femtosecond laser pulses. The modification threshold fluences for 75 μm thick films of polyimide were determined at different incident angles (0°, 20°, 30°, 45°, and 50°) for vertical and horizontal diameters. Ablation at oblique angles was investigated as such interactions are found during laser procedures with the eye that require scanning of the beam and are very important to know for the treatment of various eye diseases. Polyimide, in this study, was considered as a model for corneal sculpting. Use of ultrashort femtosecond laser pulses for high-precision patterning of the sample, without thermal damage to the surroundings, has been investigated. The relationship between the incidence angle with ablation threshold fluence, threshold energy, and beam radius are described. Also, threshold energies and threshold fluences for different thicknesses of polyimide were investigated.