Self-formed two-dimensional near-wavelength microstructures on copper induced by multipulse femtosecond vector optical fields

Abstract

Two-dimensional near-wavelength microstructures have been fabricated on copper film by femtosecond vector optical fields with different spatial polarization distribution, at a central wavelength of 800 nm, a pulse duration of ∼70  fs, and a repetition rate of 1 kHz. In the induced microstructures, fine structures with interperpendicular orientations have been observed under the irradiation of a few pulses. Under the irradiation of the multipulse femtosecond vector field, differently from on the dielectric and semiconductor surfaces, the induced microstructures on the metallic copper surface exhibit an anisotropic extending feature dependent on the polarization distribution of the vector field. The physics behind this unique feature are the anisotropic excitation and propagation of surface plasmons, caused by the coupling of the subsequent irradiation pulses with the existing microstructure.