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© 2018 SPIE. We have previously introduced a femtosecond laser micromachining-based scheme for the fabrication of anisotropic waveguides and isotropic Bragg reflection gratings in lithium niobate for application in future integrated-optic spatial light modulators. In this paper, we depict progress in fabrication and characterization of anisotropic Bragg reflection gratings fabricated in lithium niobate via Type I femtosecond laser-based permittivity modulation. We furthermore depict an electromagnetic analysis of such multilayer grating structures based around coupled-wave theory for thick holographic gratings., U.S. Army Research Laboratory (Contract FA8650-14-C-6571)

© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. In recent years, structural color has burgeoned into a vibrant and dynamic field of study. Many structurally colored organisms rely on comparatively few materials to create a large diversity of optical responses and a broad array of compelling and functional features. Scientists and engineers often explore such systems as examples of sustainable, robust solutions to complex problems. By looking to existing hierarchical material systems in biological systems, we aim to determine guidelines for fabrication of material structures with pre-determined functionality and properties. Here, we compare approaches for producing surfaces that reflect color and discuss tunable design parameters. Methods discussed include bottom up self assembly, abstracted lithographic replication of structures, and top down systematically designed surfaces. We consider existing techniques and levers available to control output, and present the components of an inverse design approach. We compare different methods on the basis of scalability, tunability, and achievable responses, and provide practical guidelines for producing bio-inspired surface structures. Our proposed designs are constrained for realizable fabrication using additive direct laser writing techniques such as two-photon polymerization that are suitable for producing arbitrary structures with sub-wavelength resolution. These evaluated and characterized structures could eventually be adapted to roll to roll or imprint based systems for scale-up and manufacturing on a commercial scale. Here we contribute to a broader vision of systematic materials design by exploring tools for generating color.

© 2018 SPIE. We have previously introduced a femtosecond laser micromachining-based scheme for the fabrication of anisotropic waveguides and isotropic Bragg reflection gratings in lithium niobate for application in future integrated-optic spatial light modulators. In this paper, we depict progress in fabrication and characterization of anisotropic Bragg reflection gratings fabricated in lithium niobate via Type I femtosecond laser-based permittivity modulation. We furthermore depict an electromagnetic analysis of such multilayer grating structures based around coupled-wave theory for thick holographic gratings.

We have previously introduced an anisotropic leaky-mode modulator as a waveguide-based, acousto-optic solution for spatial light modulation in holographic video display systems. Waveguide fabrication for these and similar surface acoustic wave devices relies on proton exchange of a lithium niobate substrate, which involves the immersion of the substrate in an acid melt. While simple and effective, waveguide depth and index profiles resulting from proton exchange are often non-uniform over the device length or inconsistent between waveguides fabricated at different times using the same melt and annealing parameters. In contrast to proton exchange, direct writing of waveguides has the appeal of simplifying fabrication (as these methods are inherently maskless) and the potential of fine and consistent control over waveguide depth and index profiles. In this paper, we explore femtosecond laser micromachining as an alternative to proton exchange in the fabrication of waveguides for anisotropic leaky-mode modulators.

Waveguide holography refers to the use of holographic techniques for the control of guided-wave light in integrated optical devices (e.g., off-plane grating couplers and in-plane distributed Bragg gratings for guided-wave optical filtering). Off-plane computer-generated waveguide holography (CGWH) has also been employed in the generation of simple field distributions for image display. We have previously depicted the design and fabrication of a binary-phase CGWH operating in the Raman-Nath regime for the purposes of near-to-eye 3-D display and as a precursor to a dynamic, transparent flat-panel guided-wave holographic video display. In this paper, we describe design algorithms and fabrication techniques for multilevel phase CGWHs for near-to-eye 3-D display.

We have previously introduced a femtosecond laser micromachining-based scheme for the fabrication of anisotropic waveguides in lithium niobate for use in a guided-wave acousto-optic spatial light modulator. This spatial light modulation scheme is extensible to off-plane waveguide holography via the integration of a Bragg reflection grating. In this paper, we present femtosecond laser-based direct-write approaches for the fabrication of (1) waveguide in-coupling gratings and (2) volume Bragg reflection gratings via permanent refractive index changes within the lithium niobate substrate. In combination with metal surface-acoustic-wave transducers, these direct-write approaches allow for complete fabrication of a functional spatial light modulator via femtosecond laser direct writing. Keywords: guided-wave acousto-optics, femtosecond laser micromachining, laser-written waveguides, laser-written gratings, lithium niobate, volume gratings, United States. Air Force. Research Laboratory (Contract FA8650-14-C-6571), MIT Media Lab Consortium

Thesis: S.M., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2016., Cataloged from PDF version of thesis., Includes bibliographical references (pages 193-200)., Due to advances in design generation and digital fabrication, novice designers are able to access more and more tools to bring their visions to life. As materials begin to evolve and change shape, having a set of rules with which to evaluate, interpret, and design them will become increasingly important. In moving towards tools that allow us to design and create our own materials these the two worlds of creation and curation must be (re)connected: in this work I strive to quantify and understand the emotive aspects of materials, such as haptic responses to, cognitive evaluation of, and emotive perception of materials; in order to understand how materials communicate meaning. My aim is to produce a set of guidelines that enable designers and scientists to communicate and help creators understand the implications of emerging material combinations. For those without the resources to conduct time intensive user studies for every project and without the intuitive knowledge of a professional, it can be very difficult to predict the implications of materials and their impact on the interaction. In this thesis, a repeatable methodology for exploring these impacts was implemented and evaluated. As a result, it will be possible to create a holistic material selection process. By combining materials to maximize properties, I plan to go beyond existing databases and fabricate objects designed to evoke specific reactions. Developing an effective methodology would enable fabrication of more engaging objects. Through this research, I plan to establish guidelines and provide a common language that enables designers to influence materials development and connect designers and researchers in a more effective way than is currently possible. This will promote unique research of materials and expand their range of use. Such a tool will enable new design practices by adding emotive factors that are not rigorously understood to the material selection and fabrication process. At its core, by Bianca C. Datta., S.M.