Polarization independent and non-reciprocal absorption in multi-layer anisotropic black phosphorus metamaterials

Deep ultraviolet spontaneous emission enhanced by layer dependent black phosphorus plasmonics

Although graphene has been the primary material of interest recently for spontaneous emission engineering through the Purcell effect, it features isotropic and thickness-independent optical properties. In contrast, the optical properties of black Phosphorus (BP) are in-plane anisotropic; which supports plasmonic modes and are thickness-dependent, offering an additional degree of freedom for control. Here we investigate how the anisotropy and thickness of BP affect spontaneous emission from a Hydrogenic emitter. We find that the spontaneous emission enhancement rate i.e. Purcell factor (PF) depends on emitter orientation, and PF at a particular frequency and distance can be controlled by BP thickness. At lower frequencies, PF increases with increasing thickness due to infrared (IR) plasmons, which then enhances visible and UV far-field spectra, even at energies greater than 10 eV. By leveraging the thickness and distance-dependent PF, deep UV emission can be switched between 103 nm or 122 nm wavelength from a Hydrogenic emitter. Additionally, we find that doping can significantly tune the PF near BP and this alteration depends on the thickness of the BP. Our work shows that BP is a promising platform for studying strong plasmon-induced light-matter interactions tunable by varying doping levels, emitter orientation, and thickness.

Engineering van der Waals Materials for Advanced Metaphotonics

The outstanding chemical and physical properties of 2D materials, together with their atomically thin nature, make them ideal candidates for metaphotonic device integration and construction, which requires deep subwavelength light-matter interaction to achieve optical functionalities beyond conventional optical phenomena observed in naturally available materials. In addition to their intrinsic properties, the possibility to further manipulate the properties of 2D materials via chemical or physical engineering dramatically enhances their capability, evoking new science on light-matter interaction, leading to leaped performance of existing functional devices and giving birth to new metaphotonic devices that were unattainable previously. Comprehensive understanding of the intrinsic properties of 2D materials, approaches and capabilities for chemical and physical engineering methods, the resulting property modifications and novel functionalities, and applications of metaphotonic devices are provided in this review. Through reviewing the detailed progress in each aspect and the state-of-the-art achievement, insightful analyses of the outstanding challenges and future directions are elucidated in this cross-disciplinary comprehensive review with the aim to provide an overall development picture in the field of 2D material metaphotonics and promote rapid progress in this fast emerging and prosperous field.

A Review: The Functional Materials-Assisted Terahertz Metamaterial Absorbers and Polarization Converters

When metamaterial structures meet functional materials, what will happen? The recent rise of the combination of metamaterial structures and functional materials opens new opportunities for dynamic manipulation of terahertz wave. The optical responses of functional materials are greatly improved based on the highly-localized structures in metamaterials, and the properties of metamaterials can in turn be manipulated in a wide dynamic range based on the external stimulation. In the topical review, we summarize the recent progress of the functional materials-based metamaterial structures for flexible control of the terahertz absorption and polarization conversion. The reviewed devices include but are not limited to terahertz metamaterial absorbers with different characteristics, polarization converters, wave plates, and so on. We review the dynamical tunable metamaterial structures based on the combination with functional materials such as graphene, vanadium dioxide (VO2) and Dirac semimetal (DSM) under various external stimulation. The faced challenges and future prospects of the related researches will also be discussed in the end.

High-performance polarization-independent black phosphorus refractive index sensors enabled by a single-layer pattern design

The in-plane orientation-dependent electrical and optical properties of two-dimensional (2D) anisotropic materials attract significant attention because of the intriguing underlying physics. However, this feature limits their further development in polarization-independent applications such as refractive index sensors and light absorbers. In this paper, polarization-independent optical properties of black phosphorous (BP) metadevices are achieved by the design of a single-layer pattern of 2D anisotropic material. Finite-difference time-domain (FDTD) simulation results indicate that the absorption spectrum remains unchanged as the polarization angle of the incident light varies from 0° to 360°. The performance of the BP metadevices when used as refractive index sensors is also studied. The results show that the polarization-independent BP sensors exhibit high sensitivity and figures of merit (FOMs). This work opens up the possibility of fabricating optically polarization-independent devices based on a single-layer pattern of 2D anisotropic material.