Lingxuan Zhang

Low-Loss Slow-Light in Periodic Plasmonic Waveguides

We have proposed and investigated two kinds of waveguide systems (i.e., dielectric-dielectric-metal and dielectric-metal-dielectric waveguides) which are able to support low-loss slow-light guided mode at telecommunication regime of 1.55 μm. Simulation results demonstrate that the propagation length of the proposed waveguides is as long as tens or even hundreds of micrometers, which is more than ten times higher than that of the traditional metal-dielectric-metal waveguides. Moreover, the proposed waveguides have better slow light performance and a figure of merit that can reach a value as high as 18 000. In addition, the slow-down factor can be flexibly tuned by adjusting the geometrical parameters. The proposed waveguide have advantages of low loss and compact configuration, which can find potential applications, such as optical buffers, in highly integrated optical communication systems.

Dispersion engineering of a As2Se3-based strip/slot hybrid waveguide for mid-infrared broadband wavelength conversion

An arsenic tri-selenide-based strip/slot hybrid waveguide with a single horizontal silica slot is proposed to achieve an extremely low and flat dispersion with three zero dispersion wavelengths. By adjusting the geometrical structural parameters of the hybrid waveguide, dispersion tailoring is fully obtained. The flat group velocity dispersion varying between ±0.08 ps2/(m) is obtained over a 1253 nm bandwidth. The parameters of effective area, nonlinear coefficient, and third-order dispersion are all investigated. Moreover, a compact on-chip all-optical wavelength converter is designed based on degenerate four-wave mixing in this waveguide. The dependencies of conversion efficiency and conversion bandwidth on the pump wavelength are discussed. The impact of pump power and signal power on the conversion efficiency is also investigated. The results show that a maximal conversion efficiency of −0.46 dB, and a 3-dB conversion bandwidth of 830 nm in the mid-infrared is achieved.

Ultra-high Q one-dimensional hybrid PhC-SPP waveguide microcavity with large structure tolerance

Abstract A photonic crystal – surface plasmon-polaritons hybrid transverse magnetic mode waveguide based on a one-dimensional optical microcavity is designed to work in the communication band. A Gaussian field distribution in a stepping heterojunction taper is designed by band engineering, and a silica layer compresses the mode field to the subwavelength scale. The designed microcavity possesses a resonant mode with a quality factor of 1609 and a modal volume of 0.01 cubic wavelength. The constant period and the large structure tolerance make it realizable by current processing techniques.

Mode Splitter Without Changing the Mode Order in SOI Waveguide

We proposed a mode splitter based on directional coupler (DC), which is capable of splitting the TE0 and TE1 modes without changing the mode order. It is found that high coupling efficiency (higher than -1 dB), low mode crosstalk (less than -16 dB), wide bandwidth (~100 nm), and large fabrication tolerance (±10 nm) can be obtained by a 24.4 μm coupling length DC structure, which is composed of a strip and a slot silicon waveguide. This design represents a first step toward mode splitter without changing the mode order, which can find important potential applications, such as optical isolation and mode division multiplexing (MDM), in large-scale photonic integrated circuits (PICs).

CMOS compatible on-chip telecom-band to mid-infrared supercontinuum generation in dispersion-engineered reverse strip/slot hybrid Si3N4 waveguide

Abstract A silicon nitride (Si3N4)-based reverse strip/slot hybrid waveguide with single vertical silica slot is proposed to acquire extremely low and flat chromatic dispersion profile. This is achieved by design and optimization of the geometrical structural parameters of the reverse hybrid waveguide. The flat dispersion varying between ±10 ps/(nm·km) is obtained over 610 nm bandwidth. Both the effective area and nonlinear coefficient of the waveguide across the entire spectral range of interest are investigated. This led to design of an on-chip supercontinuum (SC) source with −30 dB bandwidth of 2996 nm covering from 1.209 to 4.205 μm. Furthermore, we discuss the output signal spectral and temporal characteristic as a function of the pump power. Our waveguide design offers a CMOS compatible, low-cost/high yield (no photolithography or lift-off processes are necessary) on-chip SC source for near- and mid-infrared nonlinear applications.

Frequency-degenerate parametric generation through IFWM effect in nanowaveguides

We investigate highly efficient frequency-degenerate parametric generation through inverse four-wave-mixing (IFWM) in silicon nanowaveguides, which exhibits distinctly from traditional FWM phenomenon and manifests itself as a unique process producing signal and idler photon pairs with frequencies at the center of two pumps. The influences of dispersion, nonlinear coefficient and frequency detuning on the IFWM process are numerically analyzed in detail. On this basis, the optimal condition for high gain IFWM and the nanowaveguide with high nonlinearity and large normal dispersion are proposed. These results substantiate the feasibility of such frequency-degenerate parametric generation in CMOS-compatible integrated platforms, which could find important potential in signal-processing systems for photonics networks and entangled qubits generation for quantum optics.