Researches on Nanophotonics and Nanoplasmonics in Hongxing Xu’s Group in Wuhan University 2016, Volume 11, Number 2

Location
School of Physics and Technology
Wuhan University
Wuhan 430072, China

Overview
The researches on nanophotonics and nanoplasmonics in Prof. Hongxing Xu’s group are focused on exploring the light-matter interaction and the manipulation of light at the nanometer scale. Prof. Hongxing Xu is one of the pioneers of single molecule surface-enhanced Raman spectroscopy (SERS). His seminal work on the dimer of metal nanoparticles revealed that the plasmon coupling induced huge enhancement of electromagnetic field in the nanogap of two closely-spaced metal nanoparticles is the mechanism for single molecule SERS. The nanogap effect enables the amplification of weak light–matter interactions, and is the basis for many  important research directions in plasmonics, including surface-enhanced spectroscopies, optical antennas, plasmonic optical forces, plasmochemistry, quantum plasmonics and nonlinear plasmonics. Another contribution of Prof. Hongxing Xu is the researches about plasmonic nanocircuits. His group did systematic studies about the surface plasmon propagation in metal nanowire networks, and constructed a couple of nanowire-based plasmonic nanodevices, including logic gates, router, demultiplexer, and amplifier. Current research interests include nano optoelectronic devices, surface enhanced spectroscopies, ultrafast dynamics of optical systems, nanofabrication (top-down) and synthesis (bottom-up) of nanostructures, 2D topological systems, etc.

Contact
Professor Hongxing Xu
Associate Director, School of Physics and Technology
Email: hxxu@whu.edu.cn
Telephone: +86 27 68752253
Website: http://np.whu.edu.cn

Research Foci
●  Nano Optoelectronic Devices. The efforts are put on the development of fundamental nanodevices for on-chip nanophotonic circuits based on surface plasmon polaritons (SPPs), such as waveguides, couplers, modulators, routers and logic gates. The recent projects focus on high performance active nanoplasmonic/nanophotonic devices, such as ultra compact plasmonic modulators, nano light sources and detectors, and their on-chip integrations.
●  Surface Enhanced Spectroscopies. Localized surface plasmon resonances (LSPRs) in metal nanoparticles can result in strong local electromagnetic field around the nanoparticles. In the nanogaps between two coupled nanoparticles, the field enhancement is largely increased under appropriate polarization, which can enhance many weak optical phenomena, such as SERS. A nanoparticle over mirror is another representative nanogap system, which can produce intense, stable SERS signals as a result of the precise control over the nanogap. The quantum effects of surface plasmons (or quantum plasmonics), tip-enhanced Raman spectroscopy (TERS) and surface plasmon enhanced second harmonic generation are under investigation in our group.
●  Ultrafast Dynamics and Coherent Control of Optical Nanosystems. We are interested in hybrid systems composed of metals and semiconductors, organic materials and rare earth nanocompounds. Strong coupling between the collective excitations (SPPs and excitons) and their dynamics (Rabi oscillation) are being investigated, with possible applications in quantum information devices and nonlinear optics. We also focus on the dynamic studies of Fano effect, plasmon induced transparency, plasmon-assisted stimulated emissions and so on.
●  Nanofabrication and Chemical Synthesis. Nanostructures and nanodevices are prepared using state-of-art nanofabrication techniques and chemical synthesis methods. Well-developed processes include focused ion beam milling, e-beam lithography, nanoimprint lithography, UV lithography, thermal evaporation, atomic layer deposition, electroplating, reaction ion etching, various chemical wet-etching processes and hydro-thermal chemical syntheses.
●  SPPs in Topological Systems. Similar to topological insulator, p-wave or s-wave superconductor with spin-orbit coupling has nontrivial topological order under some conditions. In the topological nontrivial phase, there exist Majorana fermions as the elementary excitations. Given their exotic properties and attractive prospects for applications, topological superconductors and Majorana fermions have attracted wide theoretical interest as well as intensive consideration in experiments. Currently, we are keen on the collective excitations, especially surface plasmons in topological superconductors and insulators.