Femtosecond Laser Direct Writing of 3D Silica‐like Microstructure from Hybrid Epoxy Cyclohexyl POSS

Abstract Given the importance of epoxy cyclohexyl polyhedral oligomeric silsesquioxane (epoxy‐POSS) as a silica‐like hybrid material of optical clarity, high thermal and mechanic stability, the two‐photon initiated polymerization of epoxy‐POSS using diphenyliodonium hexafluorophosphate as photoacid generators for UV lithography and femtosecond laser direct writing is studied. The hybrid resist exhibits high thermal stability: decomposition temperatures are found at ≈350 and 400 °C when calcined in air and argon, respectively. The corresponding calcined products are found as silica‐like structures with chemical formulas of C_1.5SiO_3.5 and C₅SiO₃, evidenced by energy dispersive X‐ray analysis (EDX), fourier‐transform infrared spectroscopy (FTIR), and elemental analysis. An equation regarding the two‐photon polymerized line width as functions of intensity of laser (P_laser) and scanning speed (V) is proposed in describing the effect of Gaussian light on polymerized lines. Experimental verification of the equation is given to prove a nonlinear optical process. Line width with a resolution of 250 nm is achieved on a glass substrate, while the resolution is 400 nm when fabricated on a silicon wafer. 3D structured woodpiles are fabricated and show no volumetric shrinkage upon 300 °C calcination in air environment, demonstrating a high thermal stability.