Hybrid graphene metasurfaces for high-speed mid-infrared light modulation and single-pixel imaging

Beibei Zeng,Abul K Azad,Akhilesh Singh,Aditya D Mohite,Hou-Tong Chen,Zhiqin Huang,Yu Yao,Antoinette J Taylor,David R Smith

doi:10.1038/s41377-018-0055-4

Abstract

During the past decades, major advances have been made in both the generation and detection of infrared light; however, its efficient wavefront manipulation and information processing still encounter great challenges. Efficient and fast optoelectronic modulators and spatial light modulators are required for mid-infrared imaging, sensing, security screening, communication and navigation, to name a few. However, their development remains elusive, and prevailing methods reported so far have suffered from drawbacks that significantly limit their practical applications. In this study, by leveraging graphene and metasurfaces, we demonstrate a high-performance free-space mid-infrared modulator operating at gigahertz speeds, low gate voltage and room temperature. We further pixelate the hybrid graphene metasurface to form a prototype spatial light modulator for high frame rate single-pixel imaging, suggesting orders of magnitude improvement over conventional liquid crystal or micromirror-based spatial light modulators. This work opens up the possibility of exploring wavefront engineering for infrared technologies for which fast temporal and spatial modulations are indispensable.

Highlights

Emerging infrared technologies lie at the core of advanced photonic research because of their great potential for numerous applications
We present the experimental demonstration of hybrid graphene metasurface free-space mid-infrared modulators that enable a large intensity modulation depth of up to 90% and a high modulation speed exceeding 1 GHz over a broad bandwidth by tuning the Fermi level of graphene at a low gate voltage bias of ∼7 V
We cannot reduce the dielectric spacer thickness of a metamaterial absorber, an alternative solution is to replace a large portion of the dielectric spacer with a material that is conducting for the applied voltage bias but behaves as a dielectric in the midinfrared range. This strategy is demonstrated by using the fieldeffect transistor (FET) structure schematically shown in Fig. 1a, where the slightly conducting a semiconducting material (a-Si) layer serves as part of the gate electrode, and the gate dielectric is provided by the ultrathin Al2O3 layer to increase the capacitance

Summary

Introduction

Emerging infrared technologies lie at the core of advanced photonic research because of their great potential for numerous applications. State-of-the-art liquid crystal[8] and micromirror9-based spatial light modulators (SLMs) suffer from limitations including slow modulation speeds of a few kilohertz and complex and expensive instrumentation. In this context, active metamaterials/metasurfaces composed of planar subwavelength resonators and reconfigurable functional materials/devices have provided an alternative approach[10]. In the far-infrared region, the integration of metasurfaces and compound semiconductors (e.g., GaAs) has enabled the modulation of terahertz (THz) waves with high modulation depth and speed at room temperature[14,15,16,17] Such configurations are difficult to scale up to the midand near-infrared regions, where electronic devices fail to operate and the optical conductivity of conventional semiconductors can only be slightly adjusted[18,19], resulting in limited dynamic modulations

Methods

Results

Conclusion