3 μm aperture probes for near-field terahertz transmission microscopy

摘要

The transmission of electromagnetic waves through a sub-wavelength aperture is described by Bethe's theory. This imposes severe limitations on using apertures smaller than ∼1/100 of the wavelength for near-field microscopy at terahertz (THz) frequencies. Experimentally, we observe that the transmitted evanescent field within 1 μm of the aperture deviates significantly from the Bethe dependence of E ∝ a3. Using this effect, we realized THz near-field probes incorporating 3 μm apertures and we demonstrate transmission mode THz time-domain near-field imaging with spatial resolution of 3 μm, corresponding to λ/100 (at 1 THz).