Three-dimensional optical Yagi-Uda nanoantenna array are fabricated using Nanospherical-Lens Lithography (NLL). The fabrication method can produce nanoantenna array that covers large area and with high throughput. The individual Yagi-Uda nanoantenna is consisted with 3 Au nanodisks separated by a thin layer of SiO2 obtained through sequential evaporation using NLL. The operation wavelength of the nanoantenna is designed is in the near infrared, which can be easily controlled by varying the structural parameters during NLL. We believe the results shown in this study can be applied to obtain directional antenna of nano-emitters and receivers in the near future.
In this research, nonlinearly two-photon pumped vortex lasing was firstly observed from perovskite metasurface. The lasing occurred at room temperature is based on the quasi-bound states in the continuum (QBIC) mode with a lasing threshold of 4.5mJ/cm2. The corresponding quality factor is around 1100. The vortex lasing mode is theoretically estimated to be a magnetic dipole mode with a topological charge of +1. In addition, the finite array size effect is found to be able to modulate the lasing. Results shown in this study should provide new ways to engineer more complex vortex beam lasing.
In this study, we demonstrate the ability to exclude the thermal effect and detect the generation of non-thermal hot carriers by surface plasmon using an AlGaN/GaN high-electron-mobility transistor. We will also provide a theoretical model to explain the detecting mechanism. This proposed platform is very sensitive, which is at least two orders of magnitude more sensitive compared to the previous reports, can detect the hot carriers generated from discrete nanostructures illuminated by a continuous wave light. The quantitative measurements of hot carrier generation also open a new way to optimize the plasmonic nanoantenna design in many applications.
In this study, we will demonstrate the fabrication of a free-standing Au membrane with designed nano-patterns using Nanospherical-Lens Lithography. First, we will fabricate the Au membrane with designed nano-holes on top of the photoresist thin film. Then, the Au membrane is released in solvent and recovered on top of another thick metal membrane with larger holes. The surface plasmon resonance of the designed nano-holes is in the spectral range of mid infrared, which should be able to demonstrate surface-enhanced infrared absorption spectrum. We are currently measuring several IR-active molecules to demonstrate surface enhanced infrared absorption.
Conventional precision nanofabrication method, such as electron-beam lithography or focused-ion beam milling, can be used to fabrication of two-dimensional (2D) nanostructures. These 2D nanostructures, which are now referred as “metasurfaces”, have shown interesting optical properties and are intensely studied by researchers around the world in recent years. There are several phenomena, however, only exist in a 3D nanostructures. It is highly desirable to be able to overcome the obstacles to fabricate 3D nanostructures, which will possible open new applications for Plasmonics.
In this study, nanofabrication of various 3D nanostructures using a method combining Nanospherical-Lens Lithography and Hole Mask Lithograph will be demonstrated. The fabricated nanostructures would cover large-area and fabricated with high-throughput. The fabricated nanostructures can be made from various materials that can be evaporated. Nanostructures made from plasmonic metal, including Au, Ag and Al can be used for plasmonic applications. We will present several 3D nanostructures that can be fabricated using the proposed method. Several applications that take advantage of the fabricated nanostructures will also be introduced.
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.
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