Infrared-surface-plasmon-assisted thermal probe nanolithography using a radially polarized vortex and continuous-wave laser

Surface plasmonic polaritons (SPPs) break Abbe’s diffraction limit in the near field and provide a promising solution for high-resolution nanolithography without reducing illuminating wavelength. However, the resolution of the normal plasmonic lithography method based on ultraviolet exposure of a photoresist heavily relies on the size of the elaborate nanostructures, which usually require precise nanofabrication. Meanwhile, a high-cost pulsed laser is required as the light source to further reduce the lithography linewidth. Here, we establish a high-resolution and low-cost scanning probe nanolithography system based on the infrared surface plasmons. An easy-fabrication probe is designed by tailoring four concentric annular slits with a moderate width of 200 nm, which couples the incident radially polarized beam into SPPs, resulting in an ultra-strong spot at the tip apex. Such superfocusing mode is demonstrated to apply to the thermal field through the optical-thermal effect so as to cause the heat accumulation with a more restricted heating area, which is utilized for the thermal probe nanolithography. Experimental results indicate that the subwavelength feature with a linewidth down to 13 nm is realized using an inexpensive 1064 nm wavelength continuous-wave laser. Our scheme shows great potential in fabrication of planar optical elements with small size and high flexibility, and can also find extensive applications in areas such as single-molecule spectra, biological detection, and optical microscopy.