Precise autofocus method employing normalized fluorescence image size in a two-photon polymerization nanofabrication...

Area of Science:

• Nanotechnology
• Materials Science
• Optical Engineering

Background:

• Precise substrate positioning is critical for two-photon polymerization (TPP) nanofabrication.
• Existing autofocus methods can lack robustness and precision in TPP processes.

Purpose of the Study:

• To develop and validate a novel autofocus method for enhancing precision in TPP nanofabrication.
• To improve the positioning accuracy of the substrate surface within the laser focal spot.

Main Methods:

• A new autofocus method was developed utilizing normalized image size, calculated from the second momentum radius (SMR) of two-photon induced fluorescence (TPIF).
• The SMR of TPIF was theoretically analyzed and experimentally compared with average TPIF intensity across different laser powers.
• Experimental validation involved fabricating ascending voxel arrays and honeycomb structures.

Main Results:

• The novel autofocus method demonstrated enhanced precision and robustness in TPP.
• The method showed immunity to input laser power variations.
• A high precision of ±0.045 μm was achieved in experimental tests.
• Successful fabrication of 300 μm × 260 μm honeycomb structures confirmed practical feasibility.

Conclusions:

• The developed autofocus method significantly improves the precision and reliability of TPP nanofabrication.
• The use of SMR of TPIF offers a robust metric for autofocusing, independent of laser power fluctuations.
• This technique is suitable for fabricating complex microstructures with high fidelity.