Deep subwavelength interference lithography with tunable pattern period based on bulk plasmon polaritons.

Interference lithography based on surface plasmon polaritons has been proven to break the diffraction limit and deliver the high imaging resolution. However, most previously reported studies suffer from the inflexible pattern pitch for a certain structure ascribed to fixed excitation mode, which limits the applications in micro-/nano- fabrications. In this work, the large area deep subwavelength interference lithography with tunable pattern period based on bulk plasmon polaritons (BPPs) is proposed. By simply tuning the incident angle, the spatial frequencies of the selected BPPs modes squeezed through hyperbolic metamaterial changes correspondingly. As a result, the pitch of the interference pattern is continuously altered. The results demonstrate that one-dimensional and two-dimensional periodic patterns with pitch resolution ranging from 45 nm (λ/10) to 115 nm (λ/4) can be generated under 436 nm illumination. Additionally, the general method of designing such an interference lithography system is also discussed, which can be used for nanoscale fabrication in this fashion.