Graphene-based photonics

The past few years have seen an enormous effort in the field of graphene research. Most of the activities have so far been focused on electronic applications. Graphene-based photonics has yet not attracted that much attention, although graphene`s optical properties are not less impressive than its electrical ones. It is the purpose of the proposed research to introduce graphene as a new material into photonics and to develop optoelectronic devices based on graphene. This project will cover all aspects of modern photonics, i.e. the generation, detection, and modulation of light by using graphene as an active optical medium. Due to the high mobility of both electrons and holes, graphene offers the possibility of high-speed photonic devices that are faster than today`s state-of-the-art silicon or III-V semiconductor-based devices. Special emphasizes will hence be laid on the development of high- speed optoelectronics (photodetectors, modulators, etc.) for optical communications. Being a zero (or small) bandgap semiconductor, graphene also holds great promise for applications in the far- and mid-infrared spectral domains. It could hence play an important role in overcoming the present technological shortage of photonic devices in the long optical wavelengths regime. In particular, we will study graphene-based photodetectors for optical communications, electrically driven far- and mid-infrared light emission from p-n junctions and Landau levels, and ultrafast optical modulators. We will also explore the possibility of population inversion and lasing, and study ultrafast carrier dynamics in graphene. This project will advance state-of-the-art of graphene device technology, and will also provide new physical insights in carrier dynamics, optical response, energy level schemes and many body effects in graphene.

Two-dimensional (2D) materials exhibit strong light-matter coupling, making them potentially interesting candidates for various applications in optics and photonics. This project has dealt with the realization of novel optoelectronic devices based on 2D materials. We started our research activities first using graphene and later extended our studies to other layered crystals, including 2D semiconductors. Within this project, we suggested for the first time the potential of graphene in optical communications and demonstrated silicon waveguide-integration of 2D materials for ultrafast optical data transmission. Graphene-based data communications has meanwhile become an important sub-field in graphene research. Our main contributions to the field of 2D semiconductors include the realization of p-n junctions, which enabled the first observation of electroluminescence from a 2D material, and the first observation of a photovoltaic effect in a van der Waals heterojunction. More recently, our priority has been to take the work on 2D devices one step further and push for fully-2D material-based systems. In particular, we demonstrated integration of 2D semiconductors for the realization of both large-scale digital and analog electronic circuits, as well as systems for neuromorphic machine vision.