Advantages of optical modulation in terahertz imaging for study of graphene layers

TL;DR

This paper demonstrates that optical modulation combined with terahertz imaging significantly enhances contrast for characterizing graphene layers on silicon, enabling discrimination and development of graphene-based THz optical elements.

Contribution

It introduces a contactless THz imaging technique with optical modulation to distinguish and analyze single- and double-layer graphene on silicon substrates.

Findings

Contrast increased by an order of magnitude with optical modulation

Single- and double-layer graphene distinguished via THz contrast variation

Modulation depth of 45% achieved under laser illumination

Abstract

It was demonstrated that optical modulation together with simultaneous terahertz (THz) imaging application enables an increase in contrast by an order of magnitude illustrating hence the technique as convenient contactless tool for characterization of graphene deposited on high-resistivity silicon substrates. It was shown that the single- and double-layer graphene can be discriminated and characterized via variation of THz image contrast using a discrete frequency in a continuous wave mode. Modulation depth of 45 % has been reached, the contrast variation from 0.16 up to 0.23 is exposed under laser illumination for the single and double layer graphene, respectively. The technique was applied in the development and investigation of graphene-based optical diffractive elements for THz imaging systems.