M. Z. Alam

Propagation characteristics of hybrid modes supported by metal-low-high index waveguides and bends

Hybrid-mode waveguides consisting of a metal surface separated from a high index medium by a low index spacer have attracted much interest recently. Power is concentrated in the low index spacer region for this waveguide. Here we investigate the properties of the hybrid mode in detail and numerically demonstrate the possibility of realizing compact waveguide bends using this wave guiding scheme.

Compact and silicon-on-insulator-compatible hybrid plasmonic TE-pass polarizer

Hybrid plasmonic waveguides consisting of a metal plane separated from a high-index medium by a low-index spacer have recently attracted much interest. Here we show that, by suitably choosing the dimensions and material properties of the hybrid waveguide, a very compact and broadband TE-pass polarizer can be implemented. Finite-difference time-domain simulation indicates that the proposed device can provide large extinction ratio with low insertion loss for the TE mode.

Super mode propagation in low index medium

We investigate a novel waveguide geometry consisting of a high dielectric medium adjacent to a metal plane with a thin low dielectric spacer. The mechanism of operation is explained and simulation results are presented.

Experimental demonstration of a hybrid plasmonic transverse electric pass polarizer for a silicon-on-insulator platform

We experimentally demonstrate a transverse electric (TE)-pass polarizer using the recently proposed hybrid plasmonic waveguide. The device consists of a silicon film separated from a chromium layer by a silica spacer. The device was characterized using a tunable laser in the 1.52-1.58 μm wavelength range. For a 30 μm long polarizer, the extinction ratio in this wavelength range varies from 23 to 28 dB and the insertion loss for the TE mode is 2-3 dB. The device is compact; its fabrication is completely compatible with silicon-on-insulator technology, and its performance compares favorably against previously reported silicon-based integrated optic TE-pass polarizers.

Compact hybrid plasmonic polarization rotator

We propose a novel ultracompact (5 μm) hybrid plasmonic polarization rotator operating at telecommunication wavelength for integrated silicon photonic circuits. The polarization mode of a silicon waveguide is rotated with >14 dB polarization extinction ratio and low total insertion losses of 2.1 dB.

Compact hybrid TM-pass polarizer for silicon-on-insulator platform

Hybrid waveguides consisting of a metal plane separated from a high-index medium by a low-index spacer have recently attracted a lot of interest. TM and TE modes are guided in two different layers in these structures and their properties can be controlled in different manners by changing the waveguide dimensions and material properties. We examine the effects of different parameters on the characteristics of the two modes in such structures. We show that by properly choosing the dimensions, it is possible to cut off the TE mode while the TM mode can still be guided in a well-confined manner. Using this property of the hybrid guide, we propose a TM-pass polarizer. The proposed device is very compact and compatible with the silicon-on-insulator platform. Finite-difference time-domain simulation indicates that such a polarizer can provide a high extinction of the TE mode for a reasonable insertion loss of the TM mode.

Gain assisted surface plasmon polariton in quantum wells structures

In this paper we propose a structure to compensate the propagation loss of surface plasmons by using multiple quantum wells as a gain medium. We analyze the required gain for lossless surface plasmon propagation for different thicknesses and widths of the metallic guiding layer. We study the effects of the gain layers and a finite height superstrate on the surface plasmon mode and its propagation loss. It is shown that the gain required for lossless plasmon propagation is achievable with present technology.

Compact low loss and broadband hybrid plasmonic directional coupler.

We propose a novel broadband coupler for silicon photonics using a hybrid plasmonic waveguide section. The hybrid plasmonic waveguide is used to create an asymmetric section in the middle of a silicon nanowire waveguide coupler to introduce a phase delay to allow for a 3-dB power coupling ratio over a 150 nm bandwidth around 1.55 µm. The device is very compact (<8.5 µm) and has a low insertion loss (<0.15 dB).

Dual Polarization Measurements in the Hybrid Plasmonic Biosensors

A novel affinity biosensor is proposed based on the hybrid plasmonic platform. The proposed biosensor benefits from the high sensitivity of the surface plasmon resonance (SPR), while at the same time, it is capable of performing measurements in both the TM and TE polarizations (p- and s-polarizations). Unlike the conventional SPR biosensors, the polarization diversity of the hybrid sensor allows for decoupling of the bulk index variations in the fluidic channels (due to variations in concentration, decomposition, temperature, and so on) from the surface properties of the attached molecules. Compatibility of the proposed hybrid plasmonic biosensor with standard Si-processing techniques and the simplicity of its design are other advantages of the sensor which makes its fabrication straightforward. The best figure of merit for the biosensor is defined based on the minimum detection limit and a genetic algorithm is used to optimize the device. A method of de-convolving the surface and bulk effects is also discussed.

Theoretical Analysis of Hybrid Plasmonic Waveguide

We investigate the properties of the modes supported by the hybrid plasmonic waveguide consisting of a metal surface separated from a high-index slab by a low-index spacer. We examine the variations of the effective mode indices and field profiles of the hybrid modes for various choices of waveguide dimensions. We show that the observed variations of the modal properties can be explained from the fact that these modes result from the coupling of the surface plasmons, supported by the metal-dielectric interface, and the dielectric waveguide mode, supported by the high-index slab. The method of analysis is very general and can be used to explain the modal properties of the hybrid plasmonic waveguides for a wide range of material properties and waveguide dimensions.