Ultrafast polarization conversion with plasmonic crystals

TL;DR

This paper demonstrates femtosecond-scale polarization conversion in plasmonic nanogratings, revealing ultrafast polarization dynamics and depolarization effects through time-resolved polarimetry and an analytical model.

Contribution

It introduces the first experimental observation of ultrafast polarization conversion in plasmonic crystals with a detailed analytical explanation.

Findings

Femtosecond-scale polarization state changes observed.

Time-dependent depolarization characterized.

Four-fold enhancement of conversion with narrower measurement gates.

Abstract

Femtosecond-scale polarization state conversion is experimentally found in optical response of a plasmonic nanograting by means of time-resolved polarimetry. Simultaneous measurements of the Stokes parameters as a function of time with an averaging time-gate of 130 fs reveal a remarkable alteration of polarization state inside a single fs-pulse reflected from a plasmonic crystal. Time-dependent depolarization is experimentally found and described within an analytical model which predicts the four-fold enhancement of the polarization conversion effect with the use of the narrower gate. The effect is attributed to excitation of time-delayed polarization-sensitive surface plasmons with a highly birefringent Fano-type spectral profile.