Electronically Tunable Perfect Absorption in Graphene

Self Cite

Despite high scientific and technological potential, nanophotonics research in the mid‐infrared regime remains relatively less explored compared to other frequency bands, largely because the mid‐infrared requires a totally different set of optical materials. Polaritons in layered 2D materials, or van der Waals (vdW) crystals, provide a new set of building blocks for mid‐infrared nanophotonics. Herein, the recently reported polaritonic properties of various vdW crystals are summarized in the context of their mid‐infrared applications. Both polaritons in vdW crystals with naturally anisotropic atomic structures as well as tunable plasmon polaritons in vdW semimetals are discussed. The extreme field confinement of 2D polaritons (confinement factors ≈100) enhances both their radiative heat transfer as well as the optical coupling to the vibrational modes of molecules, allowing for highly sensitive chemical detection. Their tunable properties, meanwhile, enable dynamic modulation of mid‐infrared light to realize dynamic phase shifters, mid‐infrared modulators, and spectrally tunable thermal emitters. By vertically stacking vdW crystals, it is possible to create a large variety of new effective materials with substantially different polaritonic properties compared to their building blocks.

Section: Dynamic Light Modulation With Tunable Plasmonsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Functional Mid‐Infrared Polaritonics in van der Waals Crystals

Kim

Menabde

Brar

et al. 2019

Self Cite

Section: Polaritons In 2d Materialsmentioning

confidence: 99%

“…S. Kim et al further provided a comprehensive study on reflection‐type modulators based on graphene combined with MIM perfect absorber structure, achieving both high modulation depth and low insertion loss at the same time. As shown in top three panels in Figure b, they fabricated devices with three different structures, namely a Salisbury screen structure (type A), an MIM perfect absorber with graphene ribbons placed in the center of metal slits (type B), and another MIM structure with graphene ribbon off to one side in the metal slit (type C).…”

Section: Polaritons In 2d Materialsmentioning

confidence: 99%

Polariton Photonics Using Structured Metals and 2D Materials

Cai

Wang

et al. 2019

Polaritons are quasiparticles originating from strong interactions between photons and elementary excitations that could enable high tunability, tight electromagnetic field confinement, and large density of photonic states, making it possible to achieve novel and otherwise inaccessible functionalities. For these reasons, polaritons spawn great interest in the fields of physics, materials science, and optics for both fundamental studies as well as potential applications (e.g., modulators, photodetectors, photoluminescence, etc.). In recent years, the explosive growth of research in graphene and other 2D van der Waals materials is witnessed because they provide a new platform that substantially complements conventional metals, dielectrics, and semiconductors to investigate different polariton modes. This review highlights the works published in recent years on the topic of polariton photonics based on structured metals, graphene, and transition‐metal dichalcogenides (TMDs). The exotic optical properties of the polaritons in metallic structures and 2D van der Waals materials offer bright prospects for the development of high‐performance photonic and optoelectronic devices.

“…[2][3][4] Most of these structures, however, were passive devices and incapable of real-time adjustment. Therefore, graphene has been a promising candidate for active optoelectronics applications and absorber devices based on demonstrations in the microwave [7,8] and infrared [9][10][11][12][13][14][15][16][17][18] regimes. [5] As a 2D semiconductor, its electron mobility and Fermi level can be extensively controlled by external stimulants, such as gate voltage [6] and thus its surface conductivity.…”

mentioning

confidence: 99%

Electrically Tunable Perfect Terahertz Absorber Based on a Graphene Salisbury Screen Hybrid Metasurface

Chen

Tian

et al. 2019

has made realistic applications of the THz wave very limited. Among the functional THz devices, perfect absorbers are highly desirable in manipulating the THz wave in a number of important fields.In recent years, extensive efforts have been devoted to perfect THz absorption based on artificial structures, such as metasurfaces. [2][3][4] Most of these structures, however, were passive devices and incapable of real-time adjustment. Graphene, a 2D sheet of hexagonally arranged carbon atoms, has attracted much attention in the past decade due to its extraordinary electronic and optoelectronic properties. [5] As a 2D semiconductor, its electron mobility and Fermi level can be extensively controlled by external stimulants, such as gate voltage [6] and thus its surface conductivity. Therefore, graphene has been a promising candidate for active optoelectronics applications and absorber devices based on demonstrations in the microwave [7,8] and infrared [9][10][11][12][13][14][15][16][17][18] regimes. At THz frequencies, graphene-based absorbers were also experimentally realized. By integrating monolayer graphene into a classical Salisbury screen structure, perfect THz absorption was achieved. [19][20][21][22] However, the graphene Fermi level needed to realize perfect absorption was very high and the thickness of the absorbers were required to be around λ/4, which is too bulky for optical integration. A broadband, nearly perfect THz absorber based on patterned graphene was also reported [23] with a relatively small electrical tunability. Besides, theoretical works on graphene-based THz absorbers were proposed. [24][25][26][27][28][29] However, most studies mainly focused on simulations and calculations. Therefore, experimental realization of electrically tunable perfect THz absorption based on lightly-doped and low-quality graphene with deep subwavelength dimensions remains as an unsolved challenge.In this article, we experimentally demonstrate an electrically tunable perfect THz absorber by integrating a metallic grating into a graphene-based Salisbury screen structure. The measured results show that perfect absorption can be achieved with a more lightly doped chemical vapor deposition (CVD) graphene compared to that of the classical Salisbury screen absorber and the modulation depth of absorbance can reach up to 25%. Numerical simulations were performed using commercial full-wave numerical software showing a good agreement with the measurements. Furthermore, we proposed a simple Graphene, as a popular 2D semiconductor, with a carrier concentration that can be extensively tailored by external stimulants, such as electric bias and photoexcitation, is a promising candidate for active optoelectronics. An electrically tunable perfect terahertz absorber is presented by integrating a metallic grating into classical graphene Salisbury screen. The measurement shows that perfect absorption can be achieved for even lightly-doped graphene and a modulation depth up to 25% is realized. Numerical simulation and analytical model based...