Reduced damping of surface plasmon polaritons on silicon with intense femtosecond laser pulse

Abstract

Using intense p-polarized 100-femtosecond laser pulses, the reflectivity of a silicon grating was measured in air as a function of the incident angle. The angular dependent reflectivity was observed to abruptly decrease to create a sharp dip at a specific incident angle, representing the surface plasmon resonance (SPR) induced on the grating. We have found that the sharpness of the dip increases with increasing the laser fluence. The experimental results show that the increase in the laser fluence produces a higher density of free electrons in the surface and decreases the plasmon damping to enhance the SPR. The calculated reflectivity reproduces well the increase in the dip sharpness with increasing the electron density in the silicon grating surface.