Effect of laser intensity on temporal and spectral features of laser generated acoustic shock waves: ns versus ps laser pulses

Abstract

Evolution of acoustic shock wave (ASW) properties generated during nanosecond (ns) and picosecond (ps) laser-induced breakdown (LIB) of atmospheric air at different input intensities is presented. The intensity is varied by changing the focal geometry of ns and ps pulses. The ASW pressures are observed to follow the dynamic interplay between the plasma density and recombination of plasma species. The conversion of laser energy to acoustic energy has increased from loose to tight focusing conditions. The central frequencies have moved toward the lower side with increasing laser intensities for both ns-LIB (76-48 kHz) and ps-LIB (111.2-92.1 kHz). The angular distribution of acoustic emissions was observed to follow the laser-induced plasma spark in both ns- and ps-LIB.

Recording laser-induced sparks on Mars with the SuperCam microphone

“…From an acoustic point of view, the sensitivity of acoustic shock-wave parameters with various laser energy and focusing conditions for breakdown of atmospheric air was explored in Manikanta et al [15,16]. The peak-to-peak acoustic signal pressure increases linearly within the range of laser energies tested and decreases as the beam diameter at the focal plane increases.…”

Remotely Exploring Deeper-Into-Matter by Non-Contact Detection of Audible Transients Excited by Laser Radiation

“…As indicated in the introductory section, properties of laser radiation (pulse shape, wavelength, length, and energy) are key variables to characterize the launched acoustic waves [ 58 , 59 ]. Here, the effect of pulse energy on the acoustic frequency emissions during the laser-induced breakdown of systems was investigated.…”

Dynamics of spatially confined ns laser induced atmospheric air plasma and shock waves: visualization vis-à-vis validation

“…where α is the recombination constant, N e is the electron number density and n i is the ion number density [44,46,66,67]. However when flow is in thermal and chemical nonequilibrium state, the gas is air and the resulting plasmas have components broken into free-electrons, neutrals and ions, each one assumed to be described as an ideal gas.…”