Polarized holographic lithography system for high-uniformity microscale patterning with periodic tunability

Gaopeng Xue,Qihang Zhai,Qian Zhou,Xiaohao Wang,Haiou Lu,Kai Ni,Liyu Lin,Xinghui Li

doi:10.1038/s41378-021-00256-z

Abstract

Periodic microscale array structures play an important role in diverse applications involving photonic crystals and diffraction gratings. A polarized holographic lithography system is proposed for patterning high-uniformity microscale two-dimensional crossed-grating structures with periodic tunability. Orthogonal two-axis Lloyd’s mirror interference and polarization modulation produce three sub-beams, enabling the formation of two-dimensional crossed-grating patterns with wavelength-comparable periods by a single exposure. The two-dimensional-pattern period can also be flexibly tuned by adjusting the interferometer spatial positioning. Polarization states of three sub-beams, defining the uniformity of the interference fringes, are modulated at their initial-polarization states based on a strict full polarization tracing model in a three-dimensional space. A polarization modulation model is established considering two conditions of eliminating the unexpected interference and providing the desired identical interference intensities. The proposed system is a promising approach for fabricating high-uniformity two-dimensional crossed gratings with a relatively large grating period range of 500–1500 nm. Moreover, our rapid and stable approach for patterning period-tunable two-dimensional-array microstructures with high uniformity could be applicable to other multibeam interference lithography techniques.

Highlights

Uniform, periodic micro- and nanoscale array structures are utilized in diverse applications involving photonic crystals[1,2,3], optical metamaterials[4,5], photodetectors[6,7], and diffraction gratings[8,9,10,11]
The half-wave plates (HWPs) play an integral part in the optimization required to realize the preferred 2D interference fringes in this approach
We found that route 1 ((a)→(b)) more efficiently eliminates the influence of additional interference in the incident angle range of [0°–43.8°], whereas route 2 ((b)→(a)) affords a performance similar to route 1 in the remaining incident angle range of [43.8°–90°]

Summary

Introduction

Periodic micro- and nanoscale array structures are utilized in diverse applications involving photonic crystals[1,2,3], optical metamaterials[4,5], photodetectors[6,7], and diffraction gratings[8,9,10,11]. Two-dimensional (2D) crossed gratings with equal pitches along two orthogonal directions (the X- and Y-directions) are commonly employed in planar/surface optical encoder systems for multiaxis displacement measurements; these gratings are key components that provide a measurement reference. The grating pitch must be as small as possible to reduce the interference signal period and improve the encoder system measurement resolution[8,17]

Methods

Results

Conclusion