University of Kentucky
Surface-Plasmon Waveguide Devices for Optical Communications
Institution
University of Kentucky
Faculty Advisor/ Mentor
J. Todd Hastings
Abstract
The overall goal of this project is to determine the suitability of surface-plasmon waveguides for routing and manipulating light on an optical chip. Surface-plasmons are electromagnetic waves that propagate along the interface between dielectrics and certain metals with negative real parts of their dielectric constants. Metal stripes several nanometers thick and a few microns wide can serve as surface-plasmon waveguides. These waveguides are relatively simple to fabricate, can carry both optical and electrical signals, and are predicted to have low loss for communications wavelengths (λ ≈ 1550 nm). As a result, surface-plasmon waveguides offer an interesting alternative to dielectric waveguides for miniaturizing and integrating optical components for faster, less expensive and more robust data communications. We have developed a method to fabricate polymer-clad surface-plasmon waveguides with gold cores as small as 20 nm x 3 µm. The waveguides are fabricated on silicon substrates with a benzocyclobutene (BCB) polymer (Cyclotene®, Dow Chemical) serving as the cladding. We define the waveguide pattern in photoresist using optical lithography and a special procedure to produce an undercut resist profile. Next, we electron-beam evaporate gold over the entire substrate, and we “lift-off” the excess gold when removing the photoresist. Finally, we spin-coat another layer of BCB over the waveguides to form the top cladding. We are now in the process of fabricating a wide range of surface-plasmon waveguides and characterizing their absorption, scattering, and bending losses.
Surface-Plasmon Waveguide Devices for Optical Communications
The overall goal of this project is to determine the suitability of surface-plasmon waveguides for routing and manipulating light on an optical chip. Surface-plasmons are electromagnetic waves that propagate along the interface between dielectrics and certain metals with negative real parts of their dielectric constants. Metal stripes several nanometers thick and a few microns wide can serve as surface-plasmon waveguides. These waveguides are relatively simple to fabricate, can carry both optical and electrical signals, and are predicted to have low loss for communications wavelengths (λ ≈ 1550 nm). As a result, surface-plasmon waveguides offer an interesting alternative to dielectric waveguides for miniaturizing and integrating optical components for faster, less expensive and more robust data communications. We have developed a method to fabricate polymer-clad surface-plasmon waveguides with gold cores as small as 20 nm x 3 µm. The waveguides are fabricated on silicon substrates with a benzocyclobutene (BCB) polymer (Cyclotene®, Dow Chemical) serving as the cladding. We define the waveguide pattern in photoresist using optical lithography and a special procedure to produce an undercut resist profile. Next, we electron-beam evaporate gold over the entire substrate, and we “lift-off” the excess gold when removing the photoresist. Finally, we spin-coat another layer of BCB over the waveguides to form the top cladding. We are now in the process of fabricating a wide range of surface-plasmon waveguides and characterizing their absorption, scattering, and bending losses.