We propose a design of an ultra-broadband absorber based on a thin metamaterial nanostructure composed of a periodic array of titanium-silica (Ti-SiO₂) cubes and an aluminum (Al) bottom film. The proposed structure can achieve nearly perfect absorption with an average absorbance of 97% spanning a broad range from visible to near-infrared (i.e., from 354 nm to 1066 nm), showing a 90% absorption bandwidth over 712 nm, and the peak absorption is up to 99.8%. The excitation of superior surface plasmon resonance combined with the resonance induced by the metal-insulator-metal Fabry-Perot (FP) cavity leads to this broadband perfect absorption. The polarization and angle insensitivity is demonstrated by analyzing the absorption performance with oblique incidences for both TE- and TM-polarized waves. In addition, we discuss the impact of various metal materials and geometry structure on absorption performance in detail. The proposed broadband metamaterial absorber shows a promising prospect in applications such as solar cell, infrared detection, and imaging. Moreover, the use of a thin titanium cap and an aluminum film instead of noble metals has the potential to reduce production cost in applications.

Monolayer MoS₂ has shown excellent photoresponse properties, but its promising applications in high-sensitivity photodetection suffer from the atomic-thickness-limited adsorption and band gap-limited spectral selectivity. Here we have carried out investigations on MoS₂ monolayer-based photodetectors with and without decoration of ZnO quantum dots (ZnO-QDs) for comparison. Compared with monolayer MoS₂ photodetectors, the monolayer ZnO-QDs/MoS₂ hybrid device exhibits faster response speed (1.5 s and 1.1 s, respectively), extended broadband photoresponse range (deep UV-visible), and enhanced photoresponse in visible spectrum, such as higher responsivity over 0.084 A/W and larger detectivity of 1.05 × 10¹¹ Jones, which results from considerable injection of carries from ZnO-QDs to MoS₂ due to the formation of I-type heterostructure existing in the contact interface of them.

Photodetectors are optoelectronic devices with excellent photoelectric conversion abilities.

Highly nonlinear multimode optical integrated devices hold great promise for the emerging large-capacity mode division multiplexing (MDM) technology, and they correspondingly enable multimode optical signal processing at nodes of the MDM network. Here, we propose a highly nonlinear multimode organic-silicon slot waveguide (HN-OSSW) whose nonlinearity is greatly improved by the intensive optical field confinement in the nano-gaps filled with highly nonlinear organic material. Specifically, the achieved nonlinear coefficients of the HN-OSSW under TE0 and TE1 modes are estimated higher than 7000 W-1m-1 and 5800 W-1m-1, respectively. Also, by phase mismatch optimization, this nanostructure exhibits superior intramode four-wave mixing conversion efficiency but ignorable intermode crosstalk. Coupling efficiency of the mode multiplexer and the optimal nonlinear interaction length are discussed in detail. Based on the HN-OSSW, we then numerically demonstrate a multimode all-optical hexadecimal addition and subtraction for sixteen phase-shift keying (16PSK) signals with the operation rate of 1.28Tb/s. Six different logic operations including A+B-C, A+C-B, B+C-A, A+B, A-B and B-A are simultaneously obtained with good performance evaluations, indicating the promising prospect of the HN-OSSW applied in ultrafast multimode signal processing.

This review introduces recent advances in the materials, fabrication and application of pulsed-laser deposition for high performance photo-detectors from an overall perspective. Challenges and future development trends are also discussed.