Electrically switchable continuous phase liquid crystal Fresnel zone plate

Area of Science:

• Photonics and Optics
• Materials Science
• Liquid Crystal Technology

Background:

• Conventional binary diffractive elements have limitations in phase profile smoothness.
• Liquid crystals (LCs) offer tunable optical properties suitable for advanced optical components.

Purpose of the Study:

• To design, fabricate, and characterize continuous phase Fresnel zone plates (FZPs) using polymerizable nematic liquid crystals.
• To demonstrate the performance of continuous phase FZPs with different phase profiles (2π and 4π radians).
• To compare the efficiency and functionality of continuous phase FZPs with traditional binary FZPs.

Main Methods:

• Utilizing two-photon polymerization direct laser writing to fabricate continuous phase FZPs in LC.
• Employing polarized optical microscopy and digital holographic microscopy for structural confirmation.
• Conducting far-field optical measurements to evaluate focusing performance and voltage-dependent behavior.

Main Results:

• Continuous phase FZPs with 2π and 4π wrapped phase profiles were successfully fabricated.
• The 2π rad FZP produced a strong focal spot at 0 Vpp, switching off at higher voltages.
• The 4π rad FZP demonstrated varifocal behavior, switching between focal lengths of 24 mm and 48 mm.
• Continuous phase FZPs showed nearly double the focusing efficiency compared to binary counterparts.

Conclusions:

• Continuous phase Fresnel zone plates in liquid crystals offer superior performance over binary designs.
• The developed FZPs enable switchable, compact, varifocal, and energy-efficient optical components.
• This technology holds promise for applications in augmented/virtual reality, adaptive optics, and advanced photonic systems.