In the past half-century, surface plasmon resonance in noble metallic nanoparticles has been an important research subject. Recent advances in the synthesis, assembly, characterization, and theories of traditional and non-traditional metal nanostructures open a new pathway to the kaleidoscopic applications of plasmonics. However, accurate and precise models of plasmon resonance are still challenging, as its characteristics can be affected by multiple factors. We herein summarize the recent advances of plasmonic nanoparticles and their applications, particularly regarding the fundamentals and applications of surface plasmon resonance (SPR) in Au nanoparticles, plasmon-enhanced upconversion luminescence, and plasmonic chiral metasurfaces.

Network survivability and protection mechanisms are very important and necessary in optical networks. The long-reach passive optical network (LR-PON) proposed in this paper extends the access network to hundreds of kilometers, and it can support more optical network units by wavelength division multiplexing technology. We propose an efficient protection mechanism for the whole LR-PON. Optical encoders are used to monitor the whole network, and a network management system in the central office will initialize the protection process by monitoring the information it collects. When the network works normally, space division multiplexing technology is adopted to reduce the loss and crosstalk of signals. The designed system propagates the upstream and downstream signals in different fiber rings to mitigate the influence of Rayleigh backscattering. The proposed protection mechanism can protect the network from the multi-faults of fiber links with the designed switches. Furthermore, the loss, availability, costs, and network performance are also studied. The results obtained prove the feasibility of the proposed network. The network is costless and reliable, and it has high availability of up to 99.9992% by the protection mechanism.

We propose a liquid-crystal-based reconfigurable chiral metasurface absorber and numerically investigate its chiro-optical properties. The chiral metasurface absorber consists of a metal-insulator-metal structure with the substrate, which can strongly absorb a circularly polarized wave of one spin state and reflects that of the opposite spin, resulting a strong circular dichroism (CD). A birefringent liquid crystal (LC) is exploited to serve as the insulator layer in the metal-insulator-metal structure. We could then vary the circular state of the incident light by controlling the alignment of the LC molecules, hence inversing the CD. The simulation results show that the CD will change the sign as the LC molecules are realigned from 0° to 90°. The absorption efficiency for the specific circularly polarized wave is larger than 80% and the CD is nearly 70%. The simple and compact design of our proposed chiral metasurface absorber is especially favorable for integration, and such a reconfigurable chiral absorber could find many potential applications in biological detection/sensing, polarimetric imaging, and optical communications.

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In this paper, we design and experimentally demonstrate a 4-channel full-band WDM device based on multimode interference (MMI) in silicon dioxide material platform. The simulation and performance analysis of WDM devices are carried out by beam propagation method (BPM) and finite-difference time-domain method (FDTD). With a simple structure, the device is in small size, and easy to implement in process. The experimental results show that the device achieves wavelength separation of 1.28 μm, 1.34 μm, 1.52 μm and 1.58 μm. The insertion losses and a contrast between two channels are also displayed.

In this paper, we propose and experimentally demonstrate a multiuser wavelength-division-multiplexing passive optical network (WDM-PON) system combining with orthogonal frequency division multiple (OFDM) technique. A tunable multi-wavelength optical comb (MOC) is designed to supply flat optical lines for assisting the configuration of the proposed multiple source-free optical network units (ONUs) enhanced WDM-OFDM-PON system. Schematized by cascading a phase modulator and an intensity modulator with a recirculation loop, the MOC can output 29 ideal channel optical comb lines with the flatness of 0.85 dB. For the MOC enabled WDM-OFDM-PON system, source-free and interference-free multiuser upstream transmission over a single fiber can be efficiently supported, whilst downstream transmission channels can convey the baseband data stream and radio frequency (RF) OFDM signals simultaneously so that the proposed system can be connected to wire-line users and wireless users simultaneously.