Pulsed CO2 laser interaction with a metal surface at oblique incidence

Thermal fluence deposition and surface pressure generation produced by a CO2 laser pulse (λ=10.6 μm, during 10 μs, maximum intensity 3 MW/cm2) have been measured as a function of angle of incidence ϑ on sheet aluminum in air. We find that air plasma ignition depends on the laser beam intensity I0 only, not on the surface-normal flux I0 cosϑ. Conversely, the fluence deposition and surface pressure depend only on the product I0 cosϑ, and obey the square-root and two-thirds-power dependences observed with simple I0 variation at normal incidence.