Enhancement of optics-to-THz conversion efficiency by metallic slot waveguides.
A metallic slot waveguide, with a dielectric strip embedded within, is investigated for the purpose of enhancing the optics-to-THz conversion efficiency using the difference-frequency generation (DFG) process. To describe the frequency conversion process in such lossy waveguides, a fully-vectorial coupled-mode theory is developed. Using the coupled-mode theory, we outline the basic theoretical requirements for efficient frequency conversion, which include the needs to achieve large coupling coefficients, phase matching, and low propagation loss for both the optical and THz waves. Following these requirements, a metallic waveguide is designed by considering the trade-off between modal confinement and propagation loss. Our numerical calculation shows that the conversion efficiency in these waveguide structures can be more than one order of magnitude larger than what has been achieved using dielectric waveguides. Based on the distinct impact of the slot width on the optical and THz modal dispersion, we propose a two-step method to realize the phase matching for general pump wavelengths.
Ruan
Zhichao
Z
Ginzton Laboratory, Stanford University, Stanford, California 94305, USA. zhichao@stanford.edu
Veronis
Georgios
G
Vodopyanov
Konstantin L
KL
Fejer
Marty M
MM
Fan
Shanhui
S
D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008027:Light; D008670:Metals / Q000737:chemistry*; D008962:Models, Theoretical; D055096:Optical Devices; D012031:Refractometry / Q000295:instrumentation*; D012542:Scattering, Radiation; D020349:Surface Plasmon Resonance / Q000295:instrumentation*; D055069:Terahertz Imaging / Q000295:instrumentation*; D055053:Terahertz Radiation; D014159:Transducers
D008670:Metals