Graphene-integrated optoelectronic structures for terahertz applications

Two-dimensional nano-materials and related heterostructures are establishing themselves as intriguing material systems for the development of a new class of electronic, photonic and plasmonic devices with ad hoc-properties, that can be engineered “from scratch”. Huge potential can be envisaged in a variety of application fields, ranging from saturable absorbers to high speed photodetectors, from optical communication modules to amplitude and phase reconfigurable modulators, capable to actively manipulate THz waves. Devices exploiting single layer graphene (SLG) have an enormous potential for two main reasons: (i) its THz optical conductivity can be adjusted easily through electrostatic gating, which is the key property of reconfigurable devices; (ii) high-quality large area SLG obtained via chemical vapor deposition on Cu can be easily employed to realize hybrid devices by transferring SLG films on properly engineered structures, such as a cavities or waveguides. In this seminar, I will report on the development of graphene-on-polyimide THz modulator with a tunable-by-design optical bandwidth with excellent modulation efficiency. The electrostatic tuning of the THz conductivity is achieved through a grating gate coupler on the top of the polyimide waveguide. By coupling the modulator with a THz quantum cascade laser frequency comb, we show comb operation over a dynamic range significantly larger than the bare laser, demonstrating the efficacy of our modulator in compensating the intracavity laser dispersion.

Fabio Taddei (9038) - fabio.taddei@nano.cnr.it
Stefan Heun (9472) - stefan.heun@nano.cnr.it