We may not be using lasers on the battlefield yet, but when we do we'll know exactly how to use them to make our enemies' eyeballs explode. And how to create heat-induced bubbles inside "biological substances" (i.e., bodies). A researcher funded by the Air Force to study laser safety has inadvertently also produced a lot of data on what makes them unsafe too. His paper is ominously titled "Laser Induced Shock Waves and Vaporization in Biological Systems and Material Science."
Physicist Bernard Gerstman, author of the paper, writes:
Damage by pulsed lasers to the retina or other tissues containing strongly absorbing particles may occur through biophysical mechanisms other than simple heating. Shockwaves and bubbles have been observed experimentally, and depending on pulse duration, may be the cause of retinal damage at threshold fluence levels. We performed detailed calculations on the shockwave and bubble generation expected from pulsed lasers. For a variety of different laser pulse durations and fluences, we tabulated the expected strength of the shockwave and size of the bubble that will be generated. We also explain how these results will change for absorbing particles with different physical properties such as absorption coefficient, bulk modulus, or thermal expansion coefficient. This enables the assessment of biological danger, and possible medical benefits, for lasers of a wide range of pulse durations and energies, incident on tissues with absorbing particles with a variety of thermomechanical characteristics.
Gerstman has been studying laser interaction with eyes for many years — his main interest is in safety. But to figure out what makes lasers harm human eyes, he of course had to figure out exactly when and how that harm would occur. As Danger Room's David Hambling observes:
His findings may later be used by others with less humane motives — such as anyone interested in the anti-personnel possibilities of high-energy laser pulses which cause 'explosive bubble formation' in human flesh.
Indeed. Image via Laserforce.