Diffraction-grating beam splitter, interferometric-lithography nanopatterning with a multilongitudinal-mode diode laser

Large-area, oblique-incidence interferometric nanopatterning using a low-cost multilongitudinal-mode diode laser as the source and a spin-on-glass based diffraction-phase-mask grating beam splitter is demonstrated. The phase mask is engineered to have only two equal intensity orders (0th and −1st), dramatically simplifying the optical arrangement and decreasing the propagation distance between the beam splitter and the sample. The low-cost, high-power (150 mW) TEM00 405-nm diode laser operates with a large number of longitudinal modes, resulting in an impractical mask-to-sample-gap proximity requirement. A dual-grating-mask, achromatic interferometric scheme is introduced to extend this gap dimension to easily accessible scales. Uniform nanopatterns with a periodicity of 600 nm were fabricated over a 1 cm diameter area using this multimode diode laser. This technique is scalable and has the potential for large-area nanopatterning applications.