Laser ablation impulse generated by irradiating aluminum target with nanosecond laser pulses at normal and oblique incidence

Abstract

Impulse generation by irradiating aluminum targets with repetitive laser pulses at normal and oblique incidence was investigated using impulse measurements with a torsion pendulum at various incidence angles under different laser beam fluence conditions. The fluence varied from 5.8–20.0 J/cm2 for normal incidence. For oblique incidence, momentum coupling is sensitive to the incident angle at fluences of 6.3 J/cm2 and 9.2 J/cm2 because of target surface reflectivity changes and plume shielding effects. At fluence of 19.3 J/cm2, the fluence on the target surface becomes dominant for impulse generation compared with the angle of incidence effect in a large angular range. Beam fluence optimization for momentum coupling at oblique incidence is discussed based on the impulse characteristics obtained.