Third-harmonic generation microscopy of undeveloped photopolymerized structures

Abstract

Third-harmonic generation (THG) microscopy is demonstrated as a powerful technique 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.

Ultrafast Laser Additive Manufacturing: A Review

“…Triple harmonic generation (THG) microscopy has also been applied to visualize photopolymerized structures, which offers a similar advantage of using the same laser source at a lower average power [241]. However, the in situ results appear to have comparatively low contrast (Figure 22d).…”

“…If a portion of the fabrication beam is used to simultaneously scan the sample, it could possibly operate as a real-time monitoring technique and enable real-time process control. Triple harmonic generation (THG) microscopy has also been applied to visualize photopolymerized structures, which offers a similar advantage of using the same laser source at a lower average power [241]. However, the in situ results appear to have comparatively low contrast (Figure 22d).…”

Probing compositional engineering effects on lead-free perovskite-inspired nanocrystal thin films using correlative nonlinear optical microscopy

“…In the past, we have used this microscope to investigate NLO effects in a variety of nanostructures. [41][42][43] Briefly, a femtosecond laser (with a wavelength of 1060 nm, a repetition rate of 80 MHz, and a pulse length of 140 fs) was used as an excitation source. The laser beam output was spatially filtered, expanded, and directed towards a high numerical aperture microscope objective (Nikon CFI LU Plan Fluor Epi P, NA 0.8, magnification 50×), which was then used to focus light onto the sample mounted on a piezoscanner.…”