Fabrication of waveguide spatial light modulators via femtosecond laser micromachining

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

Progress in off-plane computer-generated waveguide holography for near-to-eye 3D display

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

Progress on characterization and optimization of leaky-mode modulators for holographic video

We give a summary of the progress we have made in the fabrication of guided wave devices for use in holographic video displays. This progress includes identifying anisotropic leaky-mode modulators as a platform for holographic display, the development of a characterization apparatus to extract key parameters from leaky-mode devices, and the identification of optimized waveguide parameters for frequency-controlled color display.United States. Air Force Research Laboratory (Contract FA8650-14-C-6571

Direct fringe writing architecture for photorefractive polymer-based holographic displays: analysis and implementation

An optical architecture for updatable photorefractive polymer-based holographic displays via the direct fringe writing of computer-generated holograms is presented. In contrast to interference-based stereogram techniques for hologram exposure in photorefractive polymer (PRP) materials, the direct fringe writing architecture simplifies system design, reduces system footprint and cost, and offers greater affordances over the types of holographic images that can be recorded. This paper reviews motivations and goals for employing a direct fringe writing architecture for photorefractive holographic imagers, describes our implementation of direct fringe transfer, presents a phase-space analysis of the coherent imaging of fringe patterns from spatial light modulator to PRP, and presents resulting experimental holographic images on the PRP resulting from direct fringe transfer.MIT Media Lab ConsortiumUnited States. Office of the Director of National Intelligence. Intelligence Advanced Research Projects Activity (Air Force Research Laboratory Contract FA8650-10-C-7034

Progress in fabrication of waveguide spatial light modulators via femtosecond laser micromachining

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 gratingsUnited States. Air Force. Research Laboratory (Contract FA8650-14-C-6571)MIT Media Lab Consortiu

Gallium phosphide optical metasurfaces for visible light applications.

There are few materials that are broadly used for fabricating optical metasurfaces for visible light applications. Gallium phosphide (GaP) is a material that, due to its optical properties, has the potential to become a primary choice but due to the difficulties in fabrication, GaP thin films deposited on transparent substrates have never been exploited. In this article we report the design, fabrication, and characterization of three different amorphous GaP metasurfaces obtained through sputtering. Although the material properties can be further optimized, our results show the potential of this material for visible applications making it a viable alternative in the material selection for optical metasurfaces