Third-Harmonic Generation Microscopy Of Undeveloped Photopolymerized Structures

Third-harmonic generation (THG) microscopy is demonstrated as a powerful tech-nique to visualize undeveloped photopolymerized microstructures within a negative photoresist film. By comparing the THG microscopy images of developed and undeveloped single-photon polymerized structures in a SU-8 film, THG was found to provide sufficient contrast for distinguishing polymerized and unpolymerized regions. This also suggests that the technique can be used as a complementary technique to visualize the effect of photoresist development where microstructure shrinkage could occur. In addition, we applied the technique to visualize a three-photon polymerized microstructure that was fabricated in the same microscopy setup. This demonstrates the potential of the technique for in situ microscopy of photopolymerized microstructures in three dimensions. (c) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement