Laser-damage performance of optics is known to be negatively affected by microscale particle contamination induced by the operational environment. In this work, we discuss our approach to quantifying particulates found inside the grating compressor chamber in the OMEGA EP Laser System. Particulate was collected at specific locations near multilayer dielectric (MLD) gratings and MLD high reflectors and subsequently characterized using optical microscopy, scanning electron microscopy, and energy dispersive x ray spectroscopy. Initial results suggest that higher concentrations are observed near the beamline ports from the target chambers.
Understanding of the laser-induced damage threshold and impact of air–vacuum cycling of the optical components in short-pulse laser systems is of fundamental importance. We report the results of a damage-testing campaign that monitored representative pulse compression grating samples that were positioned inside the OMEGA EP grating compressor vacuum chamber during normal operation and routinely damage tested on every quarterly vent for a period of about 10 years. The evolution of their damage resistance under 10-ps and 100-ps pulse lengths are associated with a significant degradation of the laser-induced damage thresholds, which is comparatively larger at 100 ps, is described.
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 a monolithic, integrated optical platform for transparent, flat-panel holographic displays suitable for near-to-eye displays in augmented reality systems. This platform employs a guided-wave acousto-optic spatial light modulator implemented in lithium niobate in conjunction with an integrated Bragg-regime reflection volume hologram. In this paper, we depict analysis of three key system attributes that inform and influence the display system performance: 1) single-axis diffraction-driven astigmatism, 2) strobed illumination to enforce acousto-optic grating stationarity, and 3) acousto-optically driven spatial Nyquist rate.
Phoropters are the most common instrument used to detect refractive errors. During a refractive exam, lenses are flipped in front of the patient who looks at the eye chart and tries to read the symbols. The procedure is fully dependent on the cooperation of the patient to read the eye chart, provides only a subjective measurement of visual acuity, and can at best provide a rough estimate of the patient’s vision. Phoropters are difficult to use for mass screenings requiring a skilled examiner, and it is hard to screen young children and the elderly etc. We have developed a simplified, lightweight automatic phoropter that can measure the optical error of the eye objectively without requiring the patient’s input. The automatic holographic adaptive phoropter is based on a Shack-Hartmann wave front sensor and three computercontrolled fluidic lenses. The fluidic lens system is designed to be able to provide power and astigmatic corrections over a large range of corrections without the need for verbal feedback from the patient in less than 20 seconds.
Near-to-eye holographic displays act to directly project wavefronts into a viewer’s eye in order to recreate 3-D scenes for augmented or virtual reality applications. Recently, several solutions for near-to-eye electroholography have been proposed based on digital spatial light modulators in conjunction with supporting optics, such as holographic waveguides for light delivery; however, such schemes are limited by the inherent low space-bandwidth product available with current digital SLMs. In this paper, we depict a fully monolithic, integrated optical platform for transparent near-to-eye holographic display requiring no supporting optics. Our solution employs a guided-wave acousto-optic spatial light modulator implemented in lithium niobate in conjunction with an integrated Bragg-regime reflection volume hologram.
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.
Recently, the fabrication of high-resolution silver nanostructures using a femtosecond laser-based direct write process in a gelatin matrix was reported. The application of direct metal writing towards feature development has also been explored with direct metal fusion, in which metal is fused onto the surface of the substrate via a femtosecond laser process. In this paper, we present a comparative study of gelatin matrix and metal fusion approaches for directly laser-written fabrication of surface acoustic wave transducers on a lithium niobate substrate for application in integrated optic spatial light modulators.
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.
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