We report on the efficient surface plasmon amplification by stimulated emission of radiation (spaser) from a gold nanorod coated with proper gain media. Numerical simulations show that the threshold of the nanorod-based spaser is nearly 1 order of magnitude lower than that of the core-shell nanosphere, which is verified by analysis with electrostatic theory. Furthermore, it is found that the nanorod-based nanosystem possesses unique optical properties such as wavelength tunability and polarization sensitivity.

As an important electron transportation phenomenon, Bloch oscillations have been extensively studied in condensed matter. Due to the similarity in wave properties between electrons and other quantum particles, Bloch oscillations have been observed in atom lattices, photonic lattices, and so on. One of the many distinct advantages for choosing these systems over the regular electronic systems is the versatility in engineering artificial potentials. Here by utilizing dissipative elements in a CMOS-compatible photonic platform to create a periodic complex potential and by exploiting the emerging concept of parity-time synthetic photonics, we experimentally realize spatial Bloch oscillations in a non-Hermitian photonic system on a chip level. Our demonstration may have significant impact in the field of quantum simulation by following the recent trend of moving complicated table-top quantum optics experiments onto the fully integrated CMOS-compatible silicon platform.

The combination of graphene and a silicon photonic crystal cavity provides an ideal structure for realizing sensitive all-optical modulation. In this paper, an all-optical tuning of a graphene-cladded photonic crystal cavity is demonstrated. A 3.5 nm resonance wavelength shift and a 20% quality factor change are observed as a 1064 nm continuous-wave control laser is focused on the cavity. The resonance wavelength shift is nearly 2 times that realized with electrical modulation and can be further improved with increasing laser power. Meanwhile, it is found that the laser power to reach the saturation absorption state of graphene is nearly 2 orders of magnitude lower than that for monolayer graphene on silica. The experimental results are attributed to optically induced transparency and hot carrier effects. This study opens up a promising way to construct a sensitive all-optical modulator, which is a necessary device in an all-optical integrated circuit, by using a graphene-cladded photonic crystal cavity.

We theoretically and experimentally study the side coupling between guided modes and cavity modes in a one-way waveguide that is composed of a regular photonic crystal and a gyromagnetic photonic crystal. At the cavity resonant wavelength, the backward mode can be completely blocked while the forward mode is only slightly influenced in the transmissivity for a specially designed waveguide. This unique light transport property can be exploited to construct a unidirectional band stop filter and a unidirectional channel-drop filter that can selectively process a light signal propagating only along a particular direction.