Superfocusing effect of V-groove metallic structure for terahertz wave

Focusing THz waves into a sub-wavelength area is a crucial issue for THz spectroscopy of minute samples and also for high-spatial resolution THz-imaging. Recently, super-focusing phenomena of THz waves, or more generally, those of electromagnetic waves are under intense investigation with theoretical and experimental studies using tapered metallic waveguiding structures. In this report we present our experimental study on a super-focusing effect of a V-groove metallic structure for THz pulsed waves with an opening angle about 10 degrees. Without coupling substrate lens, a 17% amplitude transmission of THz broadband waves (0~2.5 THz) through a 2-μm bottom-width was observed without significant waveform distortion and phase delay.