Computer-generated Volume Holograms Research Articles

Large-scale high-quality full-color computer-generated volume hologram fabricated by the stacking and tiling technique.

A technique is presented to produce very high-quality full-color holographic 3D images in large-scale computer holography, which uses over a billion pixels. In this technique, three large-scale computer-generated holograms, printed using laser lithography, are transferred to three computer-generated volume holograms (CGVH) using a method called tiling contact-copy. Then, the full-color holographic image is created by stacking the three CGVHs. We demonstrate a 10-cm square stacked CGVH that reconstructs full-parallax full-color 3D images at high quality with a viewing angle of more than 35°.

High-quality full-parallax full-color three-dimensional image reconstructed by stacking large-scale computer-generated volume holograms.

A novel technique is presented for the full-color reconstruction of large-scale computer-generated holograms (CGHs). In this method, three printed CGHs are transferred to three volume holograms at the wavelengths corresponding to red-green-blue (RGB) colors and then stacked to superimpose the RGB color images. The developed CGHs are compact and portable. The reconstructed image is sharp and vivid as compared with that developed using RGB color filters. A technique for correcting the original CGHs is proposed to compensate for the aberration caused by the thick glass substrate because the RGB images exhibit a considerable position shift owing to the aberration. Fabricated large-scale full-color CGHs are demonstrated to verify the techniques.

Dynamic wave field synthesis: enabling the generation of field distributions with a large space-bandwidth product.

We present a novel approach for the design and fabrication of multiplexed computer generated volume holograms (CGVH) which allow for a dynamic synthesis of arbitrary wave field distributions. To achieve this goal, we developed a hybrid system that consists of a CGVH as a static element and an electronically addressed spatial light modulator as the dynamic element. We thereby derived a new model for describing the scattering process within the inhomogeneous dielectric material of the hologram. This model is based on the linearization of the scattering process within the Rytov approximation and incorporates physical constraints that account for voxel based laser-lithography using micro-fabrication of the holograms in a nonlinear optical material. In this article we demonstrate that this system basically facilitates a high angular Bragg selectivity on the order of 1°. Additionally, it allows for a qualitatively low cross-talk dynamic synthesis of predefined wave fields with a much larger space-bandwidth product (SBWP ≥ 8.7 × 10(6)) as compared to the current state of the art in computer generated holography.

Direct rapid-prototyping fabrication of computer-generated volume holograms in the millimeter-wave and terahertz regime.

Computer-generated volume holograms (CGVHs) are gradient refractive index (GRIN) devices that consist of a superposition of multiple periodic diffraction gratings. Fabrication of these components for the visible range is difficult due to the small length-scale requirements but is more tenable in the terahertz (THz), as the length scales become more practical (≥ 10-5 m). We successfully utilized polymer-based 3D additive rapid-prototyping technology to fabricate, to our knowledge, the world's first 3D THz CGVH in approximately 50 minutes, using $12 of consumables. This demonstration suggests that this technique could be extended to fabricate THz volumetric optics with arbitrary electromagnetic profiles.

Aperiodic computer-generated volume holograms improve the performance of amplitude volume gratings

We study the performance of amplitude computer-generated volume holograms (CGVH) in terms of efficiency and angular/frequency selectivity. We compare CGVHs to interferometrically-recorded amplitude volume holograms. Theoretical results show that amplitude CGVHs can increase the efficiency as well as the angular and wavelength selectivity relative to optically recorded amplitude volume holograms. We fabricate the CGVHs using femtosecond laser pulse micromachining in the bulk of glass and demonstrate results consistent with the theory. These results show that aperiodic three-dimensional structures provide the degrees of freedom necessary to improve the performance of volume diffractive optics. They suggest that, under certain circumstances, a departure from the Bragg paradigm provides enhanced volume diffraction properties.

Computer-Generated Volume Holograms Optimize Degrees of Freedom in 3D Aperiodic Structures

Research continues in the construction of useful optical systems based on diffraction.

Computer-generated volume holograms fabricated by femtosecond laser micromachining

We define computer-generated volume holograms (CGVHs) as arbitrary 3D refractive index modulations designed to perform optical functions based on diffraction, scattering, and interference phenomena. CGVHs can differ dramatically from classical volume holograms in terms of coding possibilities, and from thin computer-generated holograms in terms of efficiency and selectivity. We propose an encoding technique for designing such holograms and demonstrate the concept by scanning focused femtosecond laser pulses to produce localized refractive index modifications in glass. These CGVHs show a significant increase in efficiency with thickness. Consequently, they are attractive for photonic integration with free-space and guided-wave devices, as well as for encoding spatial and temporal information.

Reduction in the reconstruction error of computer-generated holograms by photorefractive volume holography

We suggest a method for coding high-resolution computer-generated volume holograms. It involves splitting the computer-generated hologram into multiple holograms, their individual recording as volume holograms by use of the maximal resolution available from the spatial light modulator, and subsequent simultaneous reconstruction. We demonstrate the recording and the reconstruction of a computer-generated volume hologram with a space-bandwidth product much higher than the limitation imposed by the interfacing spatial light modulator. Finally, we analyze the scheduling procedure of the multiple holographic recording process in photorefractive medium in this specific application.