Due graphene’s robustness as an element in a variety of optoelectronic and photonic platforms, the material can be coupled to other resonant structures to realize functionality beyond that predicted by its constituent optical properties alone. Here we demonstrate a tunable graphene metasurface that exhibits near-unity absorptance over a narrowband range of wavelengths. We hybridize a guided mode resonance of a silicon photonic crystal with the localized surface plasmon of a graphene ribbon to produce a critically coupled system. We investigate various geometric configurations to realize a diversity of Fano lineshapes and incorporate coupled mode theory to quantitatively describe our results.
Thermal radiation is nominally broadband, incoherent, and isotropic, so controlling the spectral, temporal, and directional characteristics of thermal emission is an important frontier in imaging and chemical fingerprinting. The use of thermal metasurfaces, whose emission properties can be finely tailored, has recently become of great interest. Here we theoretically demonstrate the thermal emission of a metasurface arising from the coupled emission from a plasmonic mode in graphene nanoribbons and the guided mode resonance of a 1D photonic crystal. We also discuss the utility of a computationally cheap approach based on coupled-mode theory to model the device scattering characteristics.
Vapor condensation plays a crucial role in solar water-purification technologies. Conventional condensers in solar water-purification systems do not provide sufficient cooling power for vapor condensation, limiting the water production rate to 0.4 L m-2 hour-1. On the other hand, radiative dew condensation, a technique used by existing radiative dew condensers, only works at nighttime and is incompatible with solar water-purification technologies. Here, we develop daytime radiative condensers that reflect almost all solar radiation, and can thus create dew water even in direct sunlight. Compared to stateof- art condensers, our daytime radiative condenser doubles the production of purified water over a 24-hour period.
Efficient theoretical modeling of metasurface is highly desired for designing metasurfaces. However, most of current modeling of metasurfaces relies on full-wave numerical simulation methods that solve the Maxwell’s equations. As a metasurface typically consists of many meta-units, solving Maxwell’s equations is computationally expensive and thus inefficient for designing metasurface. Here, we develop a general theoretical framework for modeling metasurface based on the coupled mode theory (CMT), which fully describes the interaction between the meta-units and light by a simple set of coupled-mode equations. Consequently, the CMT formulism is far less computationally demanding than the Maxwell’s equations. We show that our CMT approach allows us to quickly and efficiently optimize the design of a beam-steering metagrating. The optimal design obtained from our CMT model is further validated by numerical simulation. The proposed CMT model provides an efficient tool to model and design optical devices based on multiple optical resonators.
Sensing the direction of sounds provides animals clear evolutionary advantage. For large animals in which the distance between the ears is larger or comparable to the audible sound wavelength, directional hearing is simply accomplished by recognizing the intensity and time differences of the wave impinging on the two ears. In small (subwavelength) animals, angle sensing seems instead to rely on coherent coupling of soundwaves from the two ears. Inspired by this natural design, here we present a subwavelength photodetection pixel that can measure both the intensity and the incident angle of light. It consists of two silicon nanowire optical resonators spaced at subwavelength distance that are electrically isolated but optically coupled. We exploit this effect to fabricate a subwavelength angle-sensitive pixels.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.