Origin of Laser-Induced Near-Subwavelength Ripples: Interference between Surface Plasmons and Incident Laser

TLDR

The authors propose a method to determine the dielectric constant, electron density, and collision time of the highly excited surface. Ripple formation is modeled as arising from surface‑plasmon–laser interference and grating‑assisted coupling, with period reduction due to field‑distribution and coupling effects, and the model enables extraction of dielectric parameters. Experiments show that short‑pulse laser‑induced ripples on dielectrics, semiconductors, and conductors have sub‑wavelength periods, confirming metallic behavior at damage‑threshold fluence and supporting a nano‑optics explanation, with simulations agreeing with the data.

Abstract

We show that short-pulse laser-induced classical ripples on dielectrics, semiconductors, and conductors exhibit a prominent “non-classical” characteristic—in normal incidence the periods are definitely smaller than laser wavelengths, which indicates that the simplified scattering model should be revised. Taking into account the surface plasmons (SPs), we consider that the ripples result from the initial direct SP-laser interference and the subsequent grating-assisted SP-laser coupling. With the model, the period-decreasing phenomenon originates in the admixture of the field-distribution effect and the grating-coupling effect. Further, we propose an approach for obtaining the dielectric constant, electron density, and electron collision time of the high-excited surface. With the derived parameters, the numerical simulations are in good agreement with the experimental results. On the other hand, our results confirm that the surface irradiated by short-pulse laser with damage-threshold fluence should behave metallic, no matter for metal, semiconductor, or dielectric, and the short-pulse laser-induced subwavelength structures should be ascribed to a phenomenon of nano-optics.