Hybrid Plasmonic Waveguides and Devices: Theory, Modeling and Experimental Demonstration

Xiao Sun

Mojahedi and Aitchison Groups, Photonics

Abstract:

Plasmonic wave guiding has attracted much interest because of its ability to confine light to a very small area. At optical wavelengths, metal has a complex refractive index and as a result plasmonic waveguides suffer from significant propagation loss. In an attempt to achieve a satisfactory compromise between loss and confinement, our group has proposed a hybrid plasmonic waveguide (HPWG). HPWG consist of a metal plane separated from a high index medium (silicon) by a low index spacer (silica). Power carried by the guide is concentrated in the low index region. Its fabrication is compatible with silicon on insulator (SOI) technology and it offers the possibility of integration of silicon photonics with plasmonics.

A combination of low propagation loss, high power density, and large confinement is useful for many applications. We have compared different types of plasmonic waveguides based on these criteria. The results show that HPWG offers a better compromise between loss and confinement as compared to pure plasmonic waveguides.

Another interesting property of the HPWG is its polarization diversity. In the HPWG the TE and TM modes reside in different layers. By properly adjusting the dimensions of the hybrid waveguide we can make the propagation loss of the TM mode much higher than that of the TE mode. We have designed a hybrid TE-pass polarizer using this property. Its properties such as propagation loss, extinction ratio, bandwidth, and wavelength dependency are investigated.

The polarizer was characterized using a tunable laser at telecommunication wavelength range. The device shows low insertion loss of the TE mode with a high extinction ratio for a 30 micron long hybrid section. The device is very compact; its fabrication is completely compatible with SOI technology and its performance compares favorably against previously reported silicon based integrated optic TE-pass polarizers. This is the first experimental demonstration of a compact, broadband, and SOI compatible TE-pass polarizer. It provides a possibility to shorten the integrated optical circuits where a TE-pass polarizer is needed.

Biography:

Xiao Sun is a PHD student in the photonics group under the supervision of Prof. Mo. Mojahedi and Prof. Stewart Aitchison. Her research is on the propagation properties of plasmonic waveguides.