Fabrication of subwavelength periodic nanostructures using liquid immersion Lloyd's mirror interference lithography.

We have developed a liquid immersion Lloyd's mirror interference lithography system to fabricate subwavelength periodic nanostructures. In this approach, we construct the Lloyd's mirror interferometer within a liquid medium to increase the ambient index. The light wavelength is scaled by the refractive index of the immersion fluid, reducing the minimum interference pattern period and increasing the spatial resolution. The all-liquid system ensures continuous fluid contact with the sample without an external mechanism, allows rapid adjustment of pattern period with subwavelength resolution, and retains the passive vibration-correction capability of Lloyd's mirror interferometers. Using this approach, we have successfully fabricated a grating structure with 112 nm period using a laser with 325 nm wavelength, attaining a numerical aperture of 1.45. The proposed immersion strategy can be adapted to improve pattern resolution of more complex interference lithography systems.