A novel graphene photodetector with graphene embedded in a metamaterial perfect absorber (MPA) is proposed and its light absorption property is numerically investigated. Absorption above 40% in graphene is obtained, which is over 17 times that of a bare monolayer graphene. Both horizontally and vertically cascaded MPAs integrated with graphene are also investigated.

Titanium nitride (TiN) as a refractory plasmonic material is proposed to be used as an angle-insensitive integrated broadband solar absorber and narrowband near-infrared (NIR) emitter for solar thermo-photovoltaic (STPV) application. By constructing TiN-nanopatterns/dielectric/TiN stack metamaterial, approximately 93% light absorption in a wavelength range of 0.3–0.9 μm and near unit narrowband ($\mathrm{\Delta }\lambda /\lambda \sim 0.3$) emission in NIR ($\sim 2\mathrm{\mu m}$) were demonstrated by numerical simulation. Keeping the excellent light absorption in the visible band, the emission wavelength can be easily tuned by patterning the top TiN layer into various subwavelength structures. This dual function attributes to the intrinsic absorption and plasmonic property of TiN. In such an integrated structure, broadband absorption and narrowband emission need to be balanced for an optimized power efficiency conversion. Detailed analysis has demonstrated that the STPV system based on this integrated absorber/emitter can exceed the Shockley–Queisser limit at 1000 K.

The focus of the research in metasurfaces has mainly been on the manipulation of the electromagnetic waves in free space during the past few years, which generally require thousands of subwavelength meta-atoms or even more. In this paper, we propose a conceptually new approach that chip-integrated metasurface can behave as a promising compact platform to control the propagation of guided waves when it is integrated with optical waveguide. As a proof of the concept, geometric metasurfaces consisting of only seven rotating anisotropic antennas, both metallic and dielectric, are integrated with silicon-on-insulator waveguide. Benefiting from the geometric phase shift stemming from spin-orbit interaction in metasurfaces, linearly gradient wavefront is generated along the waveguide, which is equivalent to introduce a unidirectional effective wavevector and thus leads to directional coupling. Inspired by the spin dependent gradient wavefront, opposite light flow is excited in the integrated waveguide by switching the handedness of incidence, which may provide a potential pathway to integrated polarization sorters and switchers.

Structural color filters, which obtain color selection by varying structures, have attracted extensive research interest in recent years due to the advantages of compactness, stability, multifunctions, and so on. In general, the mechanisms of structural colors are based on the interaction between light and structures, including light diffraction, cavity resonance, and surface plasmon resonance. This paper reviews recent progress of various structural color techniques and the integration applications of structural color filters in CMOS image sensors, solar cells, and display.

Solar cells incorporated with multi-coloring capability not only offer an aesthetic solution to bridge the gap between solar modules and building decorations but also open up the possibility for self-powered colorful display. In this paper, we proposed a multi-colored semi-transparent organic solar cells (TOSCs) design containing metallic nanostructures with the both high color purity and efficiency based on theoretical considerations. By employing guided mode resonance effect, the multi-colored TOSC behave like an efficient color filter that selectively transmits light with the desired wavelengths and generates electricity with light of other wavelengths. Broad range of coloring and luminosity adjusting for the transmission light can be achieved by simply tuning the period and the duty cycle of the metallic nanostructures. Furthermore, accompanying with the efficient color filtering characteristics, the optical absorption of TOSCs was improved due to the marked suppression of transmission loss at the off-resonance wavelengths and the increased light trapping in TOSCs. The mechanisms of the light guiding in photoactive layer and broadband backward scattering from the metallic nanostructures were identified to make an essential contribution to the improved light-harvesting. By enabling efficient color control and high efficiency simultaneously, this approach holds great promise for future versatile photovoltaic energy utilization.