We present a light-by-light photonic crystal configuration consisting of a bent waveguide with three embedded Kerr-type nonlinear rods and a T-branch waveguide. We show that such a configuration can also demonstrate all-optical AND gate operation with extremely high contrast between the OFF state and the ON state in its transmission. The photonic crystal configuration of all-optical light-by-light switching is simple and thus facilitates the fabrication of practical all-optical devices and further large-scale optical integration.

Dielectric loaded graphene plasmon waveguide (DLGPW) is proposed and investigated. An analytical model based on effective-index method is presented and verified by the finite element method simulations. The mode effective index, propagation loss, cutoff wavelength of higher order modes and single-mode operation region were derived at mid-infrared spectral region. By changing Fermi energy level, the propagation properties of fundamental mode could be tuned flexibly. The structure of the DLGPW is simple and easy for fabrication. It provided a new freedom to manipulate the graphene surface plasmons, which may led to new applications in actively tunable integrated optical devices.

We propose a broadband terahertz absorber consisting of nonstructured graphene loaded with arrays of elliptic dielectric cylinders. The relative bandwidth for the absorption above 90% reaches about 65%. The working mechanism of broad bandwidth mainly comes from two aspects. One is that the nonstructured graphene loaded with elliptic dielectric cylinders provides multiple discrete graphene plasmon resonances with large relative frequency interval. The other is that, for each discrete resonance, there exists a set of continuous plasmon resonances because the width of the dielectric structure varies continuously and gradiently. The broadband terahertz absorber we demonstrate here, based on geometrically gradient dielectric structures and nonstructured graphene, avoids the graphene processing, which shows great potential applications in related devices.

Graphene has unique properties which make it an ideal material for photonic and optoelectronic devices. However, the low light absorption in monolayer graphene seriously limits its practical applications. In order to greatly enhance the light absorption of graphene, many graphene-based structures have been developed to achieve perfect absorption of incident waves. In this review, we discuss and analyze various types of graphene-based perfect absorption structures in the visible to terahertz band. In particular, we review recent advances and optoelectronic applications of such structures. Indeed, the graphene-based perfect absorption structures offer the promise of solving the key problem which limits the applications of graphene in practical optoelectronic devices.

Broadband optical absorption structures in the near infrared by coupling monolayer-graphene with periodical metal structures are proposed and demonstrated numerically. Optical absorption of graphene with over-50%-absorption bandwidth up to hundreds of nanometer caused by magnetic dipole resonances and magnetic coupling effect are investigated in detail, and the demonstrated bandwidths are one order higher than those caused by dielectric guiding mode resonances. In addition, the influences of geometrical parameters of structures are fully analyzed and these demonstrated structures show angular-insensitive absorption for oblique incidence in a large angular range. The demonstrated absorption structures in this work provide new design ideas in the realization of advanced graphene-based optoelectronic devices.