Two-path solid-state interferometry using ultra-subwavelength two-dimensional plasmonic waves

We report an on-chip solid-state Mach-Zehnder interferometer operating on two-dimensional (2D) plasmonic waves at microwave frequencies. Two plasmonic paths are defined with GaAs/AlGaAs 2D electron gas 80 nm below a metallic gate. The gated 2D plasmonic waves achieve a velocity of similar to c/300 (c: free-space light speed). Due to this ultra-subwavelength confinement, the resolution of the 2D plasmonic interferometer is two orders of magnitude higher than that of its electromagnetic counterpart at a given frequency. This gigahertz proof-of-concept at cryogenic temperatures can be scaled to the terahertz-infrared range for room temperature operation, while maintaining the benefits of ultra-subwavelength confinement. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775668]