Efficient fabrication method for non-periodic microstructures using one-step two-photon lithography and a metal...

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Non-periodic microstructures are crucial for advanced optical devices like focal plane polarimeters.
• Micro-polarizer arrays (MPAs) are key components requiring precise fabrication of sub-wavelength structures.
• Existing fabrication methods can be complex and inefficient for non-periodic designs.

Purpose of the Study:

• To develop a mask-less, efficient, and high-resolution fabrication method for non-periodic microstructures.
• To design and optimize sub-wavelength micro-polarizer arrays (MPAs) for far-infrared applications.
• To demonstrate the viability of one-step two-photon lithography (TPL) for MPA fabrication.

Main Methods:

• Utilized finite element method for optimizing MPA structural parameters in the far-infrared region.
• Employed one-step two-photon lithography (TPL) with a femtosecond laser for direct photoresist exposure.
• Incorporated a metal lift-off process to create the aluminum MPA.
• Characterized fabricated MPAs using optical microscopy and atomic force microscopy (AFM).

Main Results:

• Optimized MPA design achieved TM transmittance >55% and extinction ratio ≥7 dB.
• Fabricated single-layer sub-wavelength MPAs with 3 µm period, 0.35-0.5 duty cycle, and 150 nm height.
• Demonstrated efficient fabrication via a single laser scan in TPL.
• Confirmed structural integrity and dimensions using microscopy techniques.

Conclusions:

• One-step TPL is a viable and efficient method for fabricating non-periodic microstructures.
• The developed technique enables the creation of high-performance micro-polarizer arrays.
• This approach offers a flexible and scalable solution for micro- and nanostructure fabrication.