Damage thresholds in skin and cornea using tunable ultrafast lasers

The market for ultrafast lasers (picosecond and femtosecond laser pulses) is rapidly expanding and recent forecasts estimate a total market of over $1.4 billion USD by 2019. Ultrafast lasers have many applications in biomedicine, telecommunications, defense, materials processing, and general research. Despite the growing adoption of ultrafast laser technology, current safety standards (ANSI Z136.1-2014) do not include maximum permissible exposure (MPE) values for skin using laser applications with pulse durations less than one nanosecond. Moreover, the wavelength dependence of ultrafast laser exposure in the mid-infrared region of the spectrum has not been explored. Increasing prevalence of ultrafast lasers will likely lead to an increase in the number of adverse events from accidental exposures.Our objective was to use a tunable femtosecond regenerative amplifier and an optical parametric amplifier (Spectra-Physics, Irvine, CA) to investigate laser damage characteristics and exposure thresholds for tissue phantoms mimicking the cornea and skin. The laser system covers a range of wavelengths from 1200-2900 nm with pulse energies from tens of microjoules to three millijoules. Multiple parameters including wavelength, spot size, and pulse repetition were evaluated.Additional data observing ultrafast laser exposure to ocular tissue and skin are still needed to establish MPE values for the safety standards. This initial study will help guide future experiments, standards, and promote the safe use of ultrafast laser technology across a wide range of applications and disciplines.