Hole–pillar coupled structure: a universal design model for two-dimensional gratings fabricated by dual-beam interference lithography

Dual-beam interference lithography is a core technology for two-dimensional (2D) grating fabrication. However, significant morphological deviations occur between the fabricated structures and traditional theoretical models, causing diffraction efficiency prediction discrepancies. To address this issue, this paper proposes a hole–pillar coupled design model for 2D gratings fabricated via dual-beam interference lithography. By constructing the actual three-dimensional (3D) grating morphology, the proposed model describes the grating profile evolution during fabrication accurately. Using an inverse grating design method based on the Fourier modal method, a polarization-independent 2D grating structure with high diffraction efficiency was optimized for a 670 nm working wavelength. A 2D grating with a line density of 1200 gr/mm was fabricated using dual-beam interference lithography. Experimental results show that, when transverse electric/transverse magnetic-polarized light at 670 nm is perpendicularly incident, the diffraction efficiency of the (±1,0) and (0,±1) orders exceeds 20%, with a polarization imbalance of less than 3%. Atomic force microscopy characterization reveals a correlation coefficient of 0.988 between the actual and designed grating structures, verifying the proposed model’s accuracy. The model provides a precise description of the groove profile in 2D holographic gratings, expands the grating fabrication tolerance, and provides a theoretical foundation for the development of next-generation nanoscale-precision multi-degree-of-freedom measurement systems.