High dioptric power micro-lenses fabricated by two-photon polymerization

Area of Science:

• Biomedical Optics
• Microfabrication
• Materials Science

Background:

• Specimen-induced aberrations limit in vivo optical imaging depth due to light scattering in non-homogenous tissues.
• Existing solutions often involve complex optical systems, hindering in vivo application.
• Implantable micro-optics offer a potential solution by correcting aberrations at the source.

Purpose of the Study:

• To design, fabricate, and test a single micro-optical element for in vivo imaging.
• To achieve high dioptric power and high numerical aperture (NA) with reduced complexity for biocompatibility.
• To minimize spherical aberrations in laser beams penetrating living tissues.

Main Methods:

• Designed quasi-parabolic aspheric microlenses inspired by metalens phase functions.
• Fabricated microlenses using two-photon polymerization in biocompatible SZ2080 photoresist.
• Optimized fabrication for speed and robustness, achieving optical smoothness (λ/20).

Main Results:

• Successfully fabricated high-NA (up to 1.25 in water) microlenses with varying focal lengths.
• Quantified dioptric power and magnification over an aberration-free field of view (200 × 200 µm).
• Demonstrated suitability for both linear and nonlinear excitation imaging modalities.

Conclusions:

• The developed microlenses effectively reduce tissue-induced spherical aberrations.
• Biocompatible and implantable design facilitates closer proximity to the observation volume.
• These micro-optics enhance imaging capabilities for in vivo applications.