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High-Density Topological Defect Array by Two-Step Interference Photoalignment.

Sunqian Liu¹, Inge Nys¹, Kristiaan Neyts²

¹Liquid Crystals and Photonics Group, Department of Electronics and Information Systems, Ghent University, Ghent, Belgium.

Advanced Materials (Deerfield Beach, Fla.)

|February 20, 2026

Summary

This summary is machine-generated.

Researchers developed a scalable two-step photoalignment method to create high-density liquid crystal (LC) topological defects. This technique significantly increases defect density for advanced optical applications.

Keywords:

grating interference illumination liquid crystal photoalignment topological defect

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Area of Science:

Nematic liquid crystals (LCs)
Topological defect engineering
Photonic device fabrication

Background:

Topological defects in nematic LCs are crucial for generating laser beams with orbital angular momentum.
Previous methods using spatial light modulators or digital mirror devices achieved defect arrays but limited defect density.
Pixel-based approaches restrict the achievable density of topological defects in LC devices.

Purpose of the Study:

To propose and demonstrate a scalable method for achieving a significantly higher density of topological defects in LCs.
To overcome the limitations of pixel-based photoalignment techniques.
To enable the fabrication of novel optical components with enhanced functionalities.

Main Methods:

A two-step interference illumination process was employed for photoalignment.
Step 1: Interference of two circularly polarized beams to generate a rotating director pattern.
Step 2: Two-beam interference for amplitude modulation to introduce defects, with controlled illumination doses and angles.

Main Results:

Achieved a much higher density of topological defects compared to previous methods.
Fabricated 2D defect patterns with a minimum spacing of 1.25 micrometers.
Demonstrated the generation of a high defect density grid through a scalable two-step photoalignment procedure.

Conclusions:

The proposed two-step interference illumination method is a scalable and effective technique for creating high-density LC topological defects.
This approach bridges the gap between liquid crystal topological optics and metasurfaces.
Enables the development of optical components with large-angle diffraction capabilities.