A novel phase-sensitive scanning near-field optical microscope

Phase is one of the most important parameters of electromagnetic waves. It is the phase distribution that determines the propagation, reflection, refraction, focusing, divergence, and coupling features of light, and further affects the intensity distribution. In recent years, the designs of surface plasmon polariton （SPP） devices have mostly been based on the phase modulation and manipulation. Here we demonstrate a phase sensitive multi-parameter heterodyne scanning near-field opti- cal microscope （SNOM） with an aperture probe in the visible range, with which the near field optical phase and amplitude distributions can be simultaneously obtained. A novel architecture combining a spatial optical path and a fiber optical path is employed for stability and flexibility. Two kinds of typical nano-photonic devices are tested with the system. With the phase-sensitive SNOM, the phase and amplitude distributions of any nano-optical field and localized field generated with any SPP nano-structures and irregular phase modulation surfaces can be investigated. The phase distribution and the interference pattern will help us to gain a better understanding of how light interacts with SPP structures and how SPP waves generate, localize, convert, and propagate on an SPP surface. This will be a significant guidance on SPP nano-structure design and optimization.

High-sensitivity integrated devices based on surface plasmon resonance for sensing applications

A metallic nanostructured array that scatters radiation toward a thin metallic layer generates surface plasmon resonances for normally incident light. The location of the minimum of the spectral reflectivity serves to detect changes in the index of refraction of the medium under analysis. The normal incidence operation eases its integration with optical fibers. The geometry of the arrangement and the material selection are changed to optimize some performance parameters as sensitivity, figure of merit, field enhancement, and spectral width. This optimization takes into account the feasibility of the fabrication. The evaluated results of sensitivity(1020 nm/RIU)and figure of merit(614 RIU^(-1)) are competitive with those previously reported.

A review of recent progress in plasmon-assisted nanophotonic devices

Plasmonics squeezes light into dimensions far beyond the diffraction limit by coupling the light with the surface collective oscillation of free electrons at the interface of a metal and a dielectric. Plasmonics, referred to as a promising candidate for high-speed and high- density integrated circuits, bridges microscale photonics and nanoscale electronics and offers similar speed of photonic devices and similar dimension of electronic devices. Various types of passive and active surface plasmon polariton （SPP） enabled devices with enhanced deep-subwavelength mode confinement have attracted increasing interest including waveguides, lasers and biosensors. Despite the trade-off between the unavoidable metal absorption loss and extreme light concentration, the ever-increasing research efforts have been devoted to seeking low-loss plasmon-assisted nanophotonic devices with deep-subwavelength mode confinement, which might find potential applications in high-density nanophotonic integration and efficient nonlinear signal processing. In addition, other plasmon-assisted nanophotonic devices might also promote grooming functionalities and applica- tions benefiting from plasmonics. In this review article, we give a brief overview of our recent progress in plasmon-assisted nanophotonic devices and their wide applications, including long-range hybrid plasmonic slot （LRHPS） waveguide, ultra-compact plasmonic microresonator with efficient thermo-optic tuning, high quality （Q） factor and small mode volume, compact active hybrid plasmonic ring resonator for deep-subwave- length lasing applications, fabricated hybrid plasmonic waveguides for terabit-scale photonic interconnection, and metamaterials-based broadband and selective generation of orbital angular momentum （OAM） carrying vector beams. It is believed that plasmonics opens possible new ways to facilitate next chip-scale key devices and frontier technologies.