We report studies of multiphoton mechanisms of plasmon excitation and their influence on the femtosecond-laser induced subwavelength ripple generation in large-bandgap dielectric and semiconducting transparent materials. An extended Drude Sipe formalism is applied to quantitatively estimate the real part of the dielectric function which is dependent on the carrier density. The theory is able to predict the ripple periods for selected materials in good agreement with the experimental observations. Possible limitations at very small spatial periods are also discussed.