Xiliang Peng

Improved Slow Light Capacity In Graphene-based Waveguide

We have systematically investigated the wideband slow light in two-dimensional material graphene, revealing that graphene exhibits much larger slow light capability than other materials. The slow light performances including material dispersion, bandwidth, dynamic control ability, delay-bandwidth product, propagation loss, and group-velocity dispersion are studied, proving graphene exhibits significant advantages in these performances. A large delay-bandwidth product has been obtained in a simple yet functional grating waveguide with slow down factor c/vg at 163 and slow light bandwidth Δω at 94.4 nm centered at 10.38 μm, which is several orders of magnitude larger than previous results. Physical explanation of the enhanced slow light in graphene is given. Our results indicate graphene is an excellent platform for slow light applications, promoting various future slow light devices based on graphene.

Dynamic control of wideband slow wave in graphene based waveguides.

Enlarged group index has been reported previously when surface plasmons propagate through the graphene sheet, yet a clear slow wave performance in graphene has not been explored. We proposed and numerically analyzed here for the first time to the best of our knowledge an extremely wideband slow surface wave in a graphene-based grating waveguide. The strongly delayed wave (120Δf>0.7 THz) can be dynamically controlled via the gate-voltage dependent optical properties of graphene. Our results suggest that graphene may be a very promising slow light medium, promoting future slow light devices based on graphene.

An Active Absorber Based on Nonvolatile Floating-Gate Graphene Structure

An active absorber with nearly zero static power consumption is proposed based on nonvolatile floating-gate graphene structure. Such absorber has almost no static power consumption benefited from the nonvolatile design. In such design, the central graphene can capture the tunneled electrons under the positive applied voltage, but cannot release these electrons after removing the voltage since it is electrically isolated from the external electrodes. Therefore, no extra power is needed to sustain the conductivity of graphene. Moreover, our proposed absorber exhibits an extremely strong absorption capacity. Even taking the strict condition for the bandwidth where all the absorptivity inside the bandwidth are larger than 90% as criterion, the proposed absorber provides more than 60 GHz absorption bandwidth which is twice larger than previous results. Furthermore, the proposed absorber shows high tolerance against large incidence angle (

Terahertz modulator based on graphene-embedded waveguide

60^\circ

Graphene-aluminum oxide metamaterial for a compact polarization-independent modulator

), different polarizations and nonideal factors of graphene. The results may promote various future nonvolatile absorber designs.

Plasmonic transmission lines with zero crosstalk

We reported a novel terahertz modulator based on graphene-embedded waveguide. Comparing to previous solution, the terahertz wave-matter interaction in the modulator structure is enhanced greatly. In theory, the modulation depth can be nearly 100% as the simulation results show. Experimental characterisations are carried out through continuous terahertz wave system and the terahertz time-domain spectroscopy (TDZ) system respectively. The best experimental modulation depth is 29.53%, which is much larger than state-of-art results.

Large slow light capacity in graphene-based grating waveguide

Former study shows that the graphene-embedded modulator can only work in TE mode while cannot achieve enough extinction ratio in TM mode. However, an optical modulator which can work in both TE mode and TM mode is required by the mode multiplexing technology. By simply growing a graphene-aluminum oxide metamaterial layer on the silicon waveguide, an optical-absorption modulator which can achieve a large extinction ratio in both TE mode and TM mode is designed in this letter. In addition, our modulator can achieve a very compact footprint which is only 10 μm.

Tunable slow wave waveguides based on graphene

A hybrid plasmonic parallel transmission line scheme constructed by a spatial single-mode with time-domain multi-line waveguide is presented in this paper. The proposed configuration enables a nanometer field localization with zero crosstalk between data channels. Furthermore, the proposed plasmonic transmission line shows the advantages of enabling an integrated circuits (IC) with a large number of parallel transmission channels, as well as a good robustness with respect to the fabrication tolerances.

Highly efficient graphene-on-gap modulator by employing the hybrid plasmonic effect

We have systematically investigated the slow light performances based on two-dimensional material graphene, giving the conclusion that graphene exhibits much larger slow light capability than other materials. A large delay-bandwidth product has been obtained in a simple yet functional graphene-based waveguide with slow down factor c / υg at 109 and slow light bandwidth Δω at 14.5 nm, which is several orders of magnitude larger than previous results.

Highly Efficient Graphene-Based Optical Modulator With Edge Plasmonic Effect

The dynamic control of wide band slow surface wave in a graphene-based grating waveguide is proposed here. The extreme large bandwidth and strongly delay has been obtained and the group index can be dynamically tuned.