Conditions to cancel the laser polarization dependence of a subwavelength tip

Using laser assisted atom probe tomography, we investigate the polarization dependence of the absorption coefficient of a subwavelength Al tip illuminated by an ultrashort laser pulse. In practice, we find an equilibrium condition as a function of the incident wavelength for which the atom evaporation rate becomes independent of the wave polarization. It is experimentally shown that this condition only depends on the ratio between the tip radius and the laser wavelength. Furthermore, our calculations demonstrate that a transverse local plasmon polariton mode can be resonantly excited at the tip apex.