Graphene materials and devices for terahertz science and technology

Abstract

This article reviews recent advances in graphenebased materials and devices for terahertz science and technology. The fundamental basis of the optoelectronic properties of graphene is first introduced. Then the synthesis and crystallographic characterization of graphene materials, particularly focused on the authors' original heteroepitaxial graphene-on-silicon technology, are briefly described. Then nonequilibrium carrier relaxation and recombination dynamics in optically or electrically pumped graphene is discussed to introduce the possibility of negative dynamic conductivity toward the creation of graphene terahertz lasers. Unique terahertz dynamics of the two-dimensional plasmons in graphene are also addressed.

Terahertz-wave generation using graphene: Toward new types of terahertz lasers

“…Due to a fast intraband relaxation (ps or less) and relatively slow interband recombination ()1 ps) of photoelectrons/holes, the population inversion is obtainable, as seen in Fig. 2 [39], [43]- [45].…”

“…The authors have first analytically found the possibility of terahertz gain in such systems under cryogenic conditions [12] and have recently numerically verified the occurrence of the terahertz gain even at 300 K [39]- [41]. The authors recently succeeded in observation of amplified stimulated terahertz emission in exfoliated monolayer graphene and heteroepitaxial multilayer graphene pumped by an infrared femtosecond pulse laser at room temperature, testifying to the occurrence of the terahertz negative conductivity [42]- [45]. Such an active mechanism can be utilized for creating the graphene-based coherent laser sources of terahertz radiation [14], [24]- [26].…”

“…Optical pumping with rather high photon energy of the order of ''$eV'' significantly heats the carriers, which dramatically increases the pumping threshold, preventing from population inversion [14], [39], [42]- [45]. Current injection pumping is the best solution because electrical pumping can serve any pumping energy below the order of ''meV'' when a p-i-n junction is formed like semiconductor laser diodes [13], [14].…”

Focusing ability of a microsize graphene-based cylindrical reflector in the THz range illuminated by electromagnetic plane wave

“…For wider strips one can disregard these edge effects and use the electron conductivity model developed for infinite graphene layer. In the THz range which is actively explored in today's electromagnetic-wave technology, various graphene based sources, circuits and systems are anticipated and developed [1].…”

Microscopically-Tuned Band Structure of Epitaxial Graphene through Interface and Stacking Variations Using Si Substrate Microfabrication

“…Despite the mediocre quality of initial GOS, recent improvements in GOS technology now provide a material that clearly demonstrates the linear dispersion of the π band near the Dirac point by angle-resolved PES21. The potential of GOS for electronic and photonic device applications has been demonstrated by fabricating transistors2223, terahertz photonic devices24 and even logic inverters25, a fundamental component for integrated circuits. GOS is thus becoming a promising graphene production method, based on its advantages, such as the cost of the wafer and compatibility with existing Si-based device technologies.…”