Developing highly efficient nanoscale coherent light sources is essential for advances in technological applications such as integrated photonic circuits, bioimaging, and sensing. An on-chip wavelength convertor based on second harmonic generation (SHG) would be a crucial step toward this goal, but the light-conversion efficiency would be low for small device dimensions. Here we demonstrate strongly enhanced SHG with a high conversion efficiency of 4 × 10 −5 W −1 from a hybrid plasmonic waveguide consisting of a CdSe nanowire coupled with a Au film. The strong spatial overlap of the waveguide mode with the nonlinear material and momentum conservation between the incident and reflected modes are the key factors resulting in such high efficiency. The SHG emission angles vary linearly with excitation wavelength, indicating a nonlinear steering of coherent light emission at the subwavelength scale. Our work is promising for the realization of efficient and tunable nonlinear coherent sources and opens new approaches for efficient integrated nonlinear nanophotonic devices.

Electrically driven ultrafast plasmon sources with narrow line width and wide-range wavelength tunability are desirable choices for integrated nanophotonic circuits. These have a wide range of applications from the optical communication to the data processing. Here, we demonstrate a compact metal−insulator−metal tunneling junction as a plasmon source to meet these requirements simultaneously. It is consisted by a Ag nanowire (covered by a monolayer thiol molecular) cross-placed on a Au nanostripe. Cavity plasmons are excited by inelastic tunneling electrons as applying a bias voltage. The electroluminescence spectrum shows multiple peaks with line widths as narrow as tens of nanometers due to the excitation of third to fifth order cavity plasmon modes. The linearly tunable range of the third order cavity plasmon exceeds 200 nm by varying the diameter of the Ag nanowire ∼70 nm. Our work can be further developed for the multichannels and on-chip photonic light sources.

An electrically driven optical antenna (EDOA) provides a nanoscale light-emitting scheme that is appealing for biosensors, plasmonic displays, and on-chip optoelectronic circuits. The EDOA (consisting of metal nanoparticles (NPs)) excited by inelastic tunneling electrons has attracted broad interest due to its terahertz modulation bandwidth and microelectronics-compatible dimensions. Currently, the efficient fabrication of EDOA is hampered by the ultrasmall size of NPs and the requirement of controllable preparation. Here, we overcome this limitation by accurately positioning thiol-covered gold NPs onto predesigned electrodes using dielectrophoresis trapping. The combination of a high-quality molecule tunnel barrier and the template trapping ensures that the EDOA can operate stably in ambient conditions. More importantly, the template trapping allows fabrication of EDOA with different numbers and arrangements of NPs by controlling the size and orientation of the template. This technology provides a way to fabricate controllable optoelectronic devices based on NPs and is promising for compact and smart photonic devices.

Although plenty of two-dimensional (2D) semiconductor heterostructure photodetectors have been studied, there is still a lack of systematic comparison and analysis about photovoltaic and photoconductive 2D semiconductor photodetectors. Taking advantage of the 2D semiconductor van der Waals heterostructure, this work constructs a photovoltaic (PV) GeSe/MoS2 and a photoconductive (PC) GeSe/graphene photodetector, respectively. The PC GeSe/graphene photodetector achieves relatively higher photoresponsivity (R), where R can reach up to 104 AW−1. The PV GeSe/MoS2 photodetector, by contrast, obtains a faster photoresponse speed. More importantly, the photoresponse properties of the PV GeSe/MoS2 photodetector can remain constant under the reverse bias, due to the minority carrier conduction in its depletion region at this time. The different characteristics of the two type 2D photodetectors are explored in detail, which can play a guiding role in the construction of high-performance photodetectors.

We synthesized CdS nanorods through a conventional solvothermal method and studied their photoluminescence and electric transport properties before and after annealing. High-resolution transmission electron microscopy indicated that the surface layer of the annealed CdS nanorods was well crystallized, while that of the unannealed nanorods was amorphous. Energy-dispersive x-ray spectrography, x-ray photoelectron spectrography and thermogravimetric analysis were used to demonstrate that the amorphous layer at the surface of the as-prepared nanorods was pure CdS. The photoluminescence spectra showed that after annealing the intensity of the band-edge emission increased several times and the surface state emission at 548 nm disappeared. The unannealed CdS nanorods had approximately linear I-V characteristics and the conductance suddenly increased about 100 times upon visible light illumination by a halogen lamp. The annealed CdS nanorods exhibited nonlinear conductance with a turn-on voltage at about 2.2 V. These properties show that CdS nanorods have potential applications in nanophotoelectric or sensing devices.