A prism-assisted inclined ultraviolet (UV) lithography technique is introduced for the fabrication of three-dimensional (3D) microstructures. Slanted structures with exposure angles ranging from 0 • to 60 • in SU-8 photoresist have been easily achieved without immersion in the index matching liquid. The fabrication process of multidirectional slanted structures can be simplified by one-step UV exposure using a prism with multidirectional side surfaces. A corner prism and a cone prism have been used in our experiment to demonstrate this concept. Upside-down tripod structures and horn structures have been fabricated in one-step exposures. The effective exposure area as one key parameter of the one-step exposure is analyzed for practical applications. Examples of various 3D microstructures fabricated by this method are presented.

The multi-frame superresolution technique is introduced to significantly improve the lateral resolution and image quality of spectral domain optical coherence tomography (SD-OCT). Using several sets of low resolution C-scan 3D images with lateral sub-spot-spacing shifts on different sets, the multi-frame superresolution processing of these sets at each depth layer reconstructs a higher resolution and quality lateral image. Layer by layer processing yields an overall high lateral resolution and quality 3D image. In theory, the superresolution processing including deconvolution can solve the diffraction limit, lateral scan density and background noise problems together. In experiment, the improved lateral resolution by ~3 times reaching 7.81 µm and 2.19 µm using sample arm optics of 0.015 and 0.05 numerical aperture respectively as well as doubling the image quality has been confirmed by imaging a known resolution test target. Improved lateral resolution on skin C-scan images has been demonstrated. For 3D SD-OCT imaging of human skin, fingerprint and retina layer, we used the multi-modal volume registration method to effectively estimate the lateral image shifts among different C-scans due to random minor unintended live body motion. Further processing of these images generated high lateral resolution 3D images as well as high quality B-scan images of these tissues.

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We demonstrate a nanoscale optical reinforcement concept for reversible holographic recording. The bone-muscle-like mechanism enables enhancement of holographic grating formation due to the collective alignment of liquid crystal (LC) molecules nearby photo-reconfigurable polymer backbones. The LC fluidity facilitates the ease of polymer chain transformation during the holographic recording while the polymer network stabilizes the LC collective orientation and the consequential optical enhancement after the recording. As such, the holographic recording possesses both long-term persistence and real-time rewritability.