Voxels Optimization in 3D Laser Nanoprinting.

Voxels, the 3D equivalent of 2D pixels, are obtained by individual point exposures in 3D laser nanoprinting, and are the building blocks of laser printed 3D micro/nano-structures, and their optimization is important in determining the resolution of printed 3D objects. Here, we report what is believed the first detailed study of the voxel size dependence on the z-potion of the laser spot in 3D nano-printing. That is, we study the evolution and the low-limit size (diameter and length) of voxels fabricated in the vicinity of the substrate/resin interface. We use two-photon absorption in a photopolymerizable resin, and we vary the position of the laser's focal spot, with respect to the cover glass/resin interface; i.e. in the longitudinal direction (z-direction). We found that the minimum lateral and the longitudinal sizes of complete voxels depend on the extent of penetration of the laser focal spot inside the resin. Truncated voxels, which are fabricated by partial overlap of the resin and the laser spot, allow for the fabrication of nano-features that are not diffraction limited, and we achieved near 100 nm feature sizes in our 3D fabricated objects. Our work is of central interest to 3D nanoprinting, since it addresses the spatial resolution of 3D printing technology, and might have potential impact for industry.

Photoassisted Holography in Azo Dye Doped Polymer Films.

Holographic storage is one of the most important applications in the field of optics, especially for recording and retrieving data, and information storage by interference patterns in photosensitive materials are no exception in this regard. In this work, we give evidence that holograms recorded by interference of two coherent laser beams in azo dye doped polymer films can be controlled by a third incoherent assisting laser beam. We show that light diffraction can be increased or decreased by an assisting beam depending on the respective orientation of the polarizations of the recording and the assisting beams. We also found that photomanipulation of polarization holograms, prepared by polarization modulation, does not depend on the polarization of the assisting beam, whereas, photomanipulation of holograms prepared by intensity modulation strongly depends on the polarization of the assisting beam. Photoselection is shown to play a major role in the photoassisted diffraction process.