Subwavelength nanolithography based on unidirectional excitation of surface plasmons

A subwavelength nanolithography technique based on unidirectional excitation of surface plasmons is proposed and numerically demonstrated by finite-difference time-domain analysis. Normal incident light impinging on a specially designed mask can excite two unidirectional surface plasmon waves (SPWs) with counter propagating directions on the unilluminated side. The simulation results show that the interference of these face-to-face SPWs launched by the mask could deliver about 50 nm half-pitch patterns at the operating wavelength of 365 nm, going far beyond the free space diffraction limit. This technique provides an effective fabrication method for nanostructures.