Diffractive microoptics in porous silicon oxide by grayscale lithography

Area of Science:

• Optics and Photonics
• Materials Science
• Additive Manufacturing

Background:

• Traditional microoptic fabrication often requires complex support structures, increasing time and limiting design.
• Two-photon polymerization (TPP) is a common microfabrication technique, but can be limited in speed and accuracy.
• Porous materials offer unique integration possibilities for micro-optics.

Purpose of the Study:

• To demonstrate focusing and imaging capabilities of diffractive microoptics fabricated using 2GL within porous silicon oxide.
• To showcase the advantages of 2GL over standard TPP, including improved shape accuracy and throughput.
• To present a novel fabrication approach that integrates microoptics directly into a supporting porous matrix.

Main Methods:

• Diffractive microoptics were fabricated using two-photon polymerization grayscale lithography (2GL) within a porous silicon oxide (SiO2) matrix.
• Singlet diffractive lenses (500 µm diameter, NA up to 0.6) were created and characterized by measuring focal plane and optical axis intensity distributions.
• A doublet lens system (600 µm diameter, <60 µm thickness) was designed, fabricated, and tested for imaging performance using a USAF 1951 resolution test chart.

Main Results:

• The 2GL process enabled high shape accuracy and increased fabrication throughput compared to standard TPP.
• Singlet lenses demonstrated effective focusing capabilities.
• The doublet lens system achieved a resolution of 287 line pairs per millimeter (lp/mm), validating its imaging performance.

Conclusions:

• 3D printing diffractive microoptics into porous SiO2 using 2GL offers a promising, integrated solution.
• This technique reduces fabrication time, design constraints, and increases the optically active area.
• The method holds potential for creating complex and unconventional microoptical systems.