Application of moire techniques to holography

Collective oscillation of spins in magnetic lattice known as spin waves (magnons) possess relatively long coherence length at room temperature, which makes it possible to build submicrometer scale holographic devices similar to the devices developed in optics. In this paper, we present a prototype 2-bit magnonic holographic memory. The memory consists of the double-cross waveguide structure made of Y3Fe2(FeO4)3 with magnets placed on the top of waveguide junctions. Information is encoded in the orientation of the magnets, while the read-out is accomplished by the spin waves generated by the microantennas placed on the edges of the waveguides. The interference pattern produced by multiple spin waves makes it possible to build a unique holographic image of the magnetic structure and recognize the state of each magnet. The development of magnonic holographic devices opens a new horizon for building scalable holographic devices compatible with conventional electronic devices.

Magnonic Holographic Memory

Methods for forming holographically processes polymer-liquid crystal composites (HPP7LCC) films and electrically switchable gratins utilizing HPP/ICCS are disclosed. These involve imaging a complex mask (10') which may be computer generated, containing the pattern to be imaged onto a film (12) of an HPP-LCC by use of a pair of interfering wavefronts (14A, 14B) as shown in the figure. By suitably selecting the angle between the pair of interfering wavefronts (14A, 14B), a desired submicron holographic pattern can be formed in the HPP/LCC film (12) in order to achieve optimum diffraction efficiency, with the pattern being modulated by the pattern in the mask to achieve the desired optical effect. Alternatively, the imaging may use contact lithography, where the mask (10') is in direct contact with the HPP/LCC film (12) as shown in figure 2 or the mask may be a focussing Fresnel element (10) as shown in figure 3.

Optical components containing complex diffraction gratings and methods for the fabrication thereof

Various examples of out-of-plane multicolor waveguide holography systems, methods of manufacture, and methods of use are described herein. In some examples, a multicolor waveguide holography system includes a planar waveguide to convey optical radiation between a grating coupler and a metasurface hologram. The grating coupler may be configured to couple out-of-plane optical radiation of three different color incident at three different angles into the planar waveguide. The combined multicolor optical radiation may be conveyed by the waveguide to the metasurface hologram. The metasurface hologram may diffractively decouple the three colors of optical radiation for off-plane propagation to form a multicolor holographic image in free space.

Out-of-Plane Computer-Generated Multicolor Waveguide Holography

The physical principles of holography involve the recording of the interference pattern formed between two beams of light and the subsequent illumination of that recorded pattern by one of the beams to recreate the other beam. In the specific case of holographic data storage, one beam is an information beam containing a two-dimensional pattern of 1s and Os representing digital data. Think of it as a special image. The other beam is a reference beam used to form the interference pattern that is recorded and subsequently used to reconstruct the information beam. Storage densities as high as 100 Gbits/inch2 and data rates of 1.0 Gbits/s can be realized.

History and Physical Principles

The current status of holography and its applications are discussed with some historical background to place the current activity in perspective. Basic types of holograms are described together with their properties. Applications in optical image formation include photography, microscopy, image storage and image replication. Acoustic, X-ray, electron beam and microwave holography are briefly commented upon. The second major area of application is contour generation and interferometry. Finally, the current status of holographic optical elements is assessed.

https://iopscience.iop.org/article/10.1088/0034-4885/41/5/001/pdf

B J Thompson

Papers

Applications of holography