Plasmonics for Laser Beam Shaping

This paper reviews our recent work on laser beam shaping using plasmonics. We demonstrated that by integrating properly designed plasmonic structures onto the facet of semiconductor lasers, their divergence angle can be dramatically reduced by more than one orders of magnitude, down to a few degrees. A plasmonic collimator consisting of a slit aperture and an adjacent 1-D grating can collimate laser light in the laser polarization direction; a collimator consisting of a rectangular aperture and a concentric ring grating can reduce the beam divergence both perpendicular and parallel to the laser polarization direction, thus achieving collimation in the plane perpendicular to the laser beam. The devices integrated with plasmonic collimators preserve good room-temperature performance with output power comparable to that of the original unpatterned lasers. A collimator design for one wavelength can be scaled to adapt to other wavelengths ranging from the visible to the far-IR regimes. Plasmonic collimation offers a compact and integrated solution to the problem of laser beam collimation and may have a large impact on applications such as free-space optical communication, pointing, and light detection and ranging. This paper opens up major opportunities in wavefront engineering using plasmonic structures.      

Plasmonics and enhanced magneto-optics in core-shell co-ag nanoparticles

We present theoretical and experimental studies that explain the observed strong enhancement of the magneto-optical (MO) Faraday rotation in all-metal core-shell Co-Ag nanoparticles (NPs) attributed to localized surface plasmon resonance (LSPR). We also explain why the optical absorption and MO spectra peaks appear blue-shifted with increased Co core size while keeping the NP size constant. Further, we demonstrate direct correlation between the strong LSPR induced electromagnetic fields and the enhanced MO activity of the NPs.     

石墨烯及碳纳米管实空间等离激元学的最新进展

表面等离激元是金属和掺杂半导体中光子与电子的杂化激发模式。表面等离激元的强局域电场增强效应和强限域效应可以为在亚波长尺度操控光提供新的机遇。在这篇综述中,我们将首先讨论二维石墨烯等离激元在实空间中所展示出的各种新奇物理现象的最新进展。之后我们将总结在实空间观测到的一维金属以及半导体单壁碳纳米管中的Luttinger液体等离激元。石墨烯和碳纳米管为操控等离激元响应提供了非常有前景的研究平台,同时也为探索新奇量子现象和实现纳米光电器件提供了新的可能性。     

Rational Design of Metal Nanoframes for Catalysis and Plasmonics

Recently, metal nanoframes have received increased attention due to their unique spatial and physicochemical, e.g., catalytic and plasmonic properties. So far, a variety of synthetic procedures have been developed to fabricate metal nanoframes with different shapes, sizes and compositions. Typical synthesis of metal nanoframes involves two stages: 1) formation of solid nanocrystals and 2) hollowing out the interiors and side faces. In this review, solution‐phase synthetic strategies are summarized, based on galvanic replacement reactions, oxidative etching, the Kirkendall effect, electrodeposition, and template‐assisted growth, as well as one‐pot synthesis. Their potential applications in catalysis and optical sensing are overviewed as well.     

The Quest for Zero Loss: Unconventional Materials for Plasmonics

There has been an ongoing quest to optimize the materials used to build plasmonic devices: first the elements were investigated, then alloys and intermetallic compounds, later semiconductors were considered, and, most recently, there has been interest in using more exotic materials such as topological insulators and conducting oxides. The quality of the plasmon resonances in these materials is closely correlated with their structure and properties. In general gold and silver are the most commonly specified materials for these applications but they do have weaknesses. Here, it is shown how, in specific circumstances, the selection of certain other materials might be more useful. Candidate alternatives include Ti_xN, VO₂, Al, Cu, Al-doped ZnO, and Cu–Al alloys. The relative merits of these choices and the many pitfalls and subtle problems that arise are discussed, and a frank perspective on the field is provided.     

Liquid Plasmonics: Manipulating Surface Plasmon Polaritons via Phase Transitions

This paper reports the manipulation of surface plasmon polaritons (SPPs) in a liquid plasmonic metal by changing its physical phase. Dynamic properties were controlled by solid-to-liquid phase transitions in 1D Ga gratings that were fabricated using a simple molding process. Solid and liquid phases were found to exhibit different plasmonic properties, where light coupled to SPPs more efficiently in the liquid phase. We exploited the supercooling characteristics of Ga to access plasmonic properties associated with the liquid phase over a wider temperature range (up to 30 °C below the melting point of bulk Ga). Ab initio density functional theory-molecular dynamic calculations showed that the broadening of the solid-state electronic band structure was responsible for the superior plasmonic properties of the liquid metal.