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Nanotechnology has been developed for decades and many interesting optical properties have been demonstrated. However, the major hurdle for the further development of nanotechnology depends on finding economic ways to fabricate such nanostructures in large-scale. Here, we demonstrate how to achieve low-cost fabrication using nanosphere-related techniques, such as Nanosphere Lithography (NSL) and Nanospherical-Lens Lithography (NLL). NSL is a low-cost nano-fabrication technique that has the ability to fabricate nano-triangle arrays that cover a very large area. NLL is a very similar technique that uses polystyrene nanospheres to focus the incoming ultraviolet light and exposure the underlying photoresist (PR) layer. PR hole arrays form after developing. Metal nanodisk arrays can be fabricated following metal evaporation and lifting-off processes. Nanodisk or nano-ellipse arrays with various sizes and aspect ratios are routinely fabricated in our research group. We also demonstrate we can fabricate more complicated nanostructures, such as nanodisk oligomers, by combining several other key technologies such as angled exposure and deposition, we can modify these methods to obtain various metallic nanostructures. The metallic structures are of high fidelity and in large scale. The metallic nanostructures can be transformed into semiconductor nanostructures and be used in several green technology applications.

Given the high demand for miniaturized optoelectronic circuits, plasmonic devices with the capability of generating coherent radiation at deep subwavelength scales have attracted great interest for diverse applications such as nanoantennas, single photon sources, and nanosensors. However, the design of such lasing devices remains a challenging issue because of the long structure requirements for producing strong radiation feedback. Here, a plasmonic laser made by using a nanoscale hyperbolic metamaterial cube, called hyperbolic metacavity, on a multiple quantum-well (MQW), deep-ultraviolet emitter is presented. The specifically designed metacavity merges plasmon resonant modes within the cube and provides a unique resonant radiation feedback to the MQW. This unique plasmon field allows the dipoles of the MQW with various orientations into radiative emission, achieving enhancement of spontaneous emission rate by a factor of 33 and of quantum efficiency by a factor of 2.5, which is beneficial for coherent laser action. The hyperbolic metacavity laser shows a clear clamping of spontaneous emission above the threshold, which demonstrates a near complete radiation coupling of the MQW with the metacavity. This approach shown here can greatly simplify the requirements of plasmonic nanolaser with a long plasmonic structure, and the metacavity effect can be extended to many other material systems.

Nanocavities inscribed in a gold thin film is optimized and arranged to form a metasurface. We demonstrate both numerically and experimentally that surface plasmon vortex carrying orbital angular momentum can be generated under linearly-polarized optical excitation.

Surface plasmon vortices with arbitrary pattern are synthesized via geometrical designs. The resulting vortex intensity patterns are experimentally measured using a near-field scanning optical microscope and are in good agreements as compared to numerical results.

A nanocavity in a gold thin film is optimized and arranged to form a metasurface. We numerically demonstrate that surface plasmon vortex carrying orbital angular momentum can be generated under linearly-polarized optical excitation.

We numerically demonstrate the shape (“c”, triangle and diamond) and orientation of surface plasmon vortex intensity distribution can be arbitrarily tailored within a plasmonic spiral through simple geometrical design.

Surface plasmon (SP) vortices typically have annular intensity patterns. Here we show that fractional SP vortices with arbitrary, asymmetric intensity patterns can be synthesized via simple geometric arrangements. We provide the direct experimental observations over the existence of fractional SP vortices. Triangular SP vortex intensities are synthesized by circularly polarized plane waves. On the other hand, subwavelength focusing with user-desired patterns is also experimentally demonstrated. The synthesized SP vortex and focusing patterns are experimentally measured using a near-field scanning optical microscope with uncoated fiber probe and are found in good agreements as compared to numerical results.