Huge field enhancement in microwave range achieved by λ/2000-width antennas

We observe strong electromagnetic field enhancement in extreme subwavelength antenna structures in microwave regime (Ku band, wavelength = 16.67~25 mm). Transmission spectra of antenna arrays with positive and negative geometries, fabricated by conventional photolithography technique, are measured by vector network analyzer (VNA) and waveguide setup. Estimated field enhancement of the negative antenna is ~130 and positive antenna also shows similar performance. These ultrathin-width antennas are good candidates for molecular sensing or nonlinear devices.