Microfabricated THz-regime Waveguides

Event Date: June 17, 2007
Authors: S. Sengele, B. Yang, A. Marconnet, N. Dias, K. Willis, H. Jiang, I. Knezevic, J. Booske, S. Hagness, D. van der Weide, N. Ferrier, A. Betterman, and S. Limbach
Journal: IEEE Pulse Power and Plasma Science Conference
Paper URL: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4345954
IEEE 34th International Conference on Plasma Science, 2007, pp. 648-648.

Vacuum electronic sources of THz regime (0.1-10 THz) radiation will require advanced methods to precisely fabricate miniature waveguides. We are exploring the design and fabrication of THz-regime waveguides using bulk silicon-based microfabrication, specifically, deep reactive ion etching. Due to the waveguide's dimensions it is advantageous to fabricate it in halves on two separate silicon wafers. Final assembly consists of metallizing the halves and thermocompressively bonding them together. Finding an appropriate diffusion barrier and bonding technique is vital to the success of this design and has recently been our primary focus. Along with the development of THz-regime waveguides, we are exploring a novel coupling technique that consists of a tapered silicon tip, made by wet chemical etching. These silicon tips, fabricated from square silicon rods approximately the size of the waveguide, can be fabricated with a tolerance of less than one micron by monitoring the electrolytic current in the etchant bath and controlling the submersion depth of the silicon rod via robotic controls. In conjunction with the development of the waveguides and couplers, we are also investigating how THz regime radiation interacts with metallic thin films. We are developing computational models to predict effective RF conductivity of metallic thin films at THz frequencies, including the effects of surface roughness scattering at the interfaces. Experimentally, our micro fabricated THz-regime waveguides provide us with an excellent platform for validating the model. By measuring the throughput power for different lengths of waveguide, we can determine the ohmic loss per unit length. This presentation will discuss the latest developments in all of these research efforts namely the fabrication of THz regime waveguides, coupling techniques and our investigation into electron transport in metallic thin films at THz frequencies.