Abstract

Liquid crystal polarization optics based on photoalignment technique has found pervasive applications in next-generation display platforms like virtual reality and augmented reality. Its large-scale fabrication, however, remains a big challenge due to the high demands in small feature size, fast processing speed, and defects-free alignment quality during the photoalignment process, especially for large-angle reflective devices. Here we propose a new concept of holo-imprinting based on non-contact replication of polarization pattern with a reflective liquid crystal hologram as a template. Our theoretical analysis and experimental results validate the possibility of generating a high-quality polarization pattern exploiting the self-interfering beams of reflective holograms. The method can be extended to numerous devices, from transmissive to reflective, from small angle to large angle, and from grating, lens, to freeform optics. Its widespread impact on the fabrication of liquid crystal polarization optics for advanced display and imaging systems is foreseeable.

Highlights

  • Polarization optics based on photo-aligned liquid crystal (LC) enables the versatile modulations of light with various functionalities and dynamic tunability, from transmissive/reflective diffractive optical elements[1–3], to selforganized soft photonic crystals[4,5] and stimuli-response devices[4,6]

  • For the feasibility study, the size of our fabricated master holograms is only ~1 cm in diameter, a much larger master hologram for mass-production can be readily obtained by combining the interferometer with a translation stage

  • The pattern size of an individual optical element may be in the order of several centimeters, like, for example, the out-coupler grating for a waveguide augmented reality (AR) display combiner, or the combiner lens for Maxwellian-AR display

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Summary

Introduction

Polarization optics based on photo-aligned liquid crystal (LC) enables the versatile modulations of light with various functionalities and dynamic tunability, from transmissive/reflective diffractive optical elements[1–3], to selforganized soft photonic crystals[4,5] and stimuli-response devices[4,6]. The LC layer (only a few microns) placed atop selfassembles into a functional optical layer with excellent image quality and diffraction efficiency. Such an ultra-thin LC film is extremely attractive for optical systems pursuing a compact form factor. The LC alignment methods have evolved from early mechanical buffing to non-contact photoalignment based on linear photo-polymerization[8,9] for high-resolution multi-domain liquid crystal displays (LCDs), to azo-dye-based photoalignment for polarization holography[2,10]. Due to the simple fabrication process and excellent alignment quality, azo-dye-based photoalignment has lately been extensively adopted to fabricate various types of LC polarization optics[2]

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