Pulse-Duration-Dependent Mid-Infrared Laser Ablation for Biological Applications

There are significant benefits to medical laser surgeries performed with mid-infrared wavelengths, including the ability to select laser parameters in order to minimize photochemical and thermal collateral damage. It has been shown that a wavelength of 6.1 μm is optimal when high ablation efficiency and minimal collateral damage is desired in biological soft tissues. Historically, free electron lasers were the only option for ablating tissue at this wavelength due to their ample pulse energy and average power. In recent years, new sources are being developed for this wavelength that can successfully ablate tissue. These alternative sources have different pulse structures and pulse durations than free electron lasers, motivating investigation of how these parameters affect the ablation process. Here, we present the pulse duration dependence for mid-IR laser ablation of biological tissues at a wavelength of 6.1 μm on a tissue phantom of cooked egg white. The crater shape, depth, and volume all changed in a significant, nonmonotonic manner as the laser pulse duration was increased from 100 ns to 5 μs.