Trends in melanin microcavitation threshold in the near-infrared

In the field of laser bioeffects, the type of cellular damage induced depends on the laser wavelength and exposure duration. In the nanosecond (ns) to microsecond (μs) regime, melanin microcavitation is known to be the damage mechanism responsible for retinal threshold lesions. This process has been studied for visible and near-infrared (NIR) wavelengths out to 1.06 micrometer (μm), for ns to ps laser exposures. We expanded this investigation regime by exposing melanin granules to nanosecond pulses in the 1.06 to 1.4-μm range to look at the trend in microcavitation threshold. We used strobe microphotography to determine when microcavitation bubbles were created with varying wavelength and pulse energy. These trends are discussed in light of the proposed changes to the safe exposure limits in the NIR regime.