Carbon Nanomaterial Devices for Infrared and Terahertz Technology

William Marsh Rice University, Houston TX

Investigators

Abstract

Although technologies for the manipulation and detection of light in the visible and near-infrared range of the electromagnetic spectrum have seen extraordinary success, devices for the mid-infrared (MIR) and terahertz (THz) range of the electromagnetic spectrum have yet to reach maturity. Expanding access to this frequency range holds promise for applications in the fields of health, energy, space, communications, imaging, and sensing. Carbon nanomaterials have unique physical properties, which make them suitable candidates for applications in the MIR and THz range. Depending on the type of carbon nanotubes, they strongly absorb light in the entire frequency range from the visible to the THz region. One can select the type of carbon nanotube for a given application by selecting for a particular frequency range. Graphene absorbs light over the entire electromagnetic spectrum as well, and furthermore, one can tune the strength of absorption in the MIR and THz range by applying a gate voltage. Graphene also has a high electrical conductivity, making it suitable for high operation speed. The goal of this research is to develop devices for the detection and manipulation of light in the MIR and THz region, using sheets of aligned carbon nanotubes, graphene, and a combination of the two utilizing the best properties of each material. Technical description: Carbon nanomaterials such as single-wall carbon nanotubes (SWCNTs) and graphene are low-dimensional materials with electronic, photonic, and magnetic properties that are suitable for a variety of optoelectronic device applications especially in the less technologically developed mid-infrared (MIR) and terahertz (THz) spectral ranges. Depending on chirality, SWCNTs strongly absorb radiation across the entire electromagnetic spectrum. Recently, the fabrication of wafer-scale films of aligned, densely packed, and chirality-enriched SWCNTs has been developed using slow vacuum filtration of SWCNT solution. These films maintain the extraordinary properties of one-dimensional/anisotropic SWCNTs in a macroscopically aligned film, bringing the extraordinary properties of the nanomaterial to a technologically useful macroscopic scale. For instance, depending on the polarization of radiation with respect to the nanotube alignment in the film, one can strongly absorb or completely transmit incident radiation over a broad frequency range, including the MIR and THz regions. Graphene also absorbs light in the entire electromagnetic spectrum, but the carrier density can be tuned by electrostatic gating to control the absorption of light in the MIR and THz regions. Furthermore, the high electrical conductivity of graphene leads to high operation speed. The goal of this research is to create hyperbolic metamaterials, photodetectors, and modulators in the MIR and THz range, utilizing aligned SWCNT films, graphene, and a combination of the two materials.