Based on the successful single-photon 3D light field photolithography we demonstrated in the last year, we extend the methodology to femtosecond 3D light field lithography. Compared with our previous single-photon work with UV LED light, using femtosecond light and the associated two-photon light absorption in 3D light field lithography can cure photoresist only around designed voxel locations in a 3D space. Such a two-photon scheme can prevent the unwilling curing of photoresists along the optical paths of rays before arriving at designed voxel locations, which is observed in our previous UV LED-based single-photon 3D light field lithography. The experimental scheme of femtosecond two-photon 3D light field lithography starts from delivering uniform femtosecond laser pulses to a spatial light modulator. The designed pixel map is presented on the spatial light modulator and then delivered to a microlens array to construct a 3D virtual image in the free space. By compressing the 3D virtual image in a photoresist layer with a microscope system, we can successfully generate different microscale 3D patterns without relying on scanning processes as in traditional 3D lithography. In this study, we present preliminary results of (a) algorithms developed to generated 3D patterns with femtosecond light, which should satisfy additional constraints when femtosecond light is used, and (b) 3D patterns generated in photoresists with femtosecond two-photon 3D light field lithography.

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