Signal beam

About: Signal beam is a research topic. Over the lifetime, 1881 publications have been published within this topic receiving 20717 citations.

Volume holographic data storage system using a beam pattern from a tapered optical fiber

Abstract: A volume holographic data storage(VHDS) system incorporates therein a tapered optical fiber for generating a speckle beam pattern from the tapered optical fiber for increasing the amount of holograms to be stored into a photorefractive crystal. The VHDS system includes a light source for generating a coherent light beam, a beam splitter for splitting the coherent light beam into a reference and a signal beams, a storage medium for storing the multiple holograms thereinto, a mirror for directing the signal beam to the storage medium, a coupler for coupling the reference beam to the tapered optical fiber, wherein one end of the tapered optical fiber has a tapered structure to give perturbation in the form of a speckle pattern to the reference beam from the tapered optical fiber and the reference beam containing the speckle pattern travels to the storage medium after being transmitted through the tapered structure, thereby the speckle pattern reference beam interfering with the signal beam in the storage medium.

Hologram reconstructing apparatus and hologram reconstructing method

Abstract: A hologram reconstructing apparatus configured to irradiate a hologram recording medium that stores an interference pattern of a signal beam spatially modulated by data displayed on a spatial modulator and a reference beam emitted simultaneously with the signal beam with a reconstructing reference beam and to reconstruct data by capturing a reconstruction signal beam generated at the hologram recording medium being irradiated includes an image pickup unit that receives a partial reconstruction signal beam that constitutes part of the reconstruction signal beam by a full light-receiving plane; and a moving unit that relatively move the light-receiving surface of the image pickup means within an irradiation range of the reconstruction signal beam. All information included in the reconstruction signal beam is reconstructed by receiving the reconstruction signal beam corresponding to the entire irradiation range by relatively moving the image pickup means within the irradiation range of the reconstruction signal beam.

Nonlinear negative refraction by difference frequency generation

Abstract: Negative refraction has attracted much interest for its promising capability in imaging applications. Such an effect can be implemented by negative index meta-materials, however, which are usually accompanied by high loss and demanding fabrication processes. Recently, alternative nonlinear approaches like phase conjugation and four wave mixing have shown advantages of low-loss and easy-to-implement, but associated problems like narrow accepting angles can still halt their practical applications. Here, we demonstrate theoretically and experimentally a scheme to realize negative refraction by nonlinear difference frequency generation with wide tunability, where a thin Beta barium borate slice serves as a negative refraction layer bending the input signal beam to the idler beam at a negative angle. Furthermore, we realize optical focusing effect using such nonlinear negative refraction, which may enable many potential applications in imaging science.

Optical retrodirective tracking system approach using an array of phase conjugators for communication and power transmission

Abstract: A new concept for a retrodirective tracking system applicable for communication and power transmission is proposed. In the proposed concept, the power transmitter utilizes a receiver's pilot signal to obtain information about its direction by conjugating the signal's phase inside a nonlinear medium. Power is therefore transmitted back to the receiver by the phase-conjugated signal beam. The power can be concentrated by an array of phase conjugators, which provides a large aperture so that the intensity can be increased on the receiver's photovoltaic panels compared to a single element. Controlling the phase and the direction of the readout beams in the four-wave-mixing process provides control over the interference pattern, its position, and its size. A numerical analysis is given for the phase and spot size control, and measurements with two Co-doped SrxBa1−xNb2O6 (Co:SBN) crystals confirm the occurrence of interference that is achieved for the case of two beams.

Apparatus and method for recording digital data on a holographic storage system

Abstract: A holographic apparatus includes a mask for modulating a signal beam to generate a modulated signal beam; a conical prism, which has a cone portion and a base portion, for refracting a reference beam to generate a refracted reference beam, wherein the refracted reference beam interferes with the modulated signal beam in a holographic medium to thereby record data thereon, the base portion facing the holographic medium. The holographic apparatus can be miniaturized by a positional relationship between the conical prism and the holographic medium.