Gelatin ablation wavelength dependency in the range of 5.6–6.7 μm using a mid-infrared Free Electron Laser

Efficient and precise ablation of soft tissue is needed for non-invasive dermatological and corneal surgeries. Previous research has revealed that smooth and efficient cutting of certain soft tissues and gelatin is possible using a Free Electron Laser (FEL) with a wavelength of λ=6.45 μm, tuned to the amide-II band of protein. Gelatin ablation experiments have been carried out using a mid-infrared FEL within the waveband λ=5.6–6.7 μm by changing the primary absorbers such as water (λ=6.1 μm) and protein (λ=6.45 μm). The gelatin with 80 wt% water was efficiently ablated by FEL irradiation with the waveband λ=∼5.95–6.19 μm. On the other hand, using irradiation within λ=∼6.4–6.6 μm, many small bubbles were observed in the irradiated volume, and the gelatin was not ablated but significantly melted. Thus, it was found that the most effective wavelength was ∼6.1 μm, not ∼6.45 μm, in order to cut soft tissue with a high water concentration at the expense of surface smoothness.