Large Scale Indium Tin Oxide (ITO) One Dimensional Gratings for Ultrafast Signal Modulation in the Visible

We present a photophysical study on an indium tin oxide (ITO) one dimensional grating, realized using femtosecond micromachining technology, a technology very industrially accessible. The geometries, dimensions and pitch of the various gratings analyzed are obtained by means of direct ablation in a controlled atmosphere of a homogeneous thin layer of ITO deposited on a glass substrate. The pitch has been selected in order to obtain a higher order of the photonic band gap in the visible. By means of ultrafast pump-probe spectroscopy we characterize both the plasmon and inter-band temporal dynamics. We observe a large optical non-linearity of ITO grating in the visible range, where the photonic band gap occurs, when pumped at the surface plasmon resonance in the near infrared (1500 nm). All together we show the possibility of all-optical signal modulation with heavily doped semiconductors in their transparency window with a picosecond response time through the formation of ITO grating structures.