Analyzing chaos in the pressure generated by laser absorption by microparticles

Abstract

Upon absorption of laser energy, microparticles can convert the absorbed energy into temperature rises, pressure waves, and vaporization. All of these will affect the surrounding material as well as damaging the absorbing particle. The pressure signals display especially complex behavior because of two competing time scales: the duration of the laser pulse and the characteristic mechanical oscillation time of the absorber. As the pulse duration is lengthened, the pressure signals become increasingly more complicated. Using power spectra and Lyapunov exponents, we show that for pulse durations greater than the characteristic oscillation time, the pressure signals are chaotic. The chaotic nature of the pressure signal presents potentially dangerous uncertainty when using longer laser pulses in biomedical and engineering applications.