Signal beam

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

Optical information processing apparatus and optical information recording and reproducing methods using the same

Abstract: There is provided an optical information recording apparatus comprising: a light source; a light modulator in which a reference beam pattern for converting a beam emitted from the light source into a reference beam and a signal beam pattern for converting the beam into a signal beam are formed and varies the reference beam pattern at the time of multiplexing and recording optical information; and a lens allowing optical information to be recorded in an optical information storage medium by means of interference between the reference beam and the signal beam when the signal beam and the reference beam emitted from the light modulator are irradiated to the optical information storage medium. Accordingly, in an optical information processing apparatus using a coaxial optical system, it is possible to more efficiently multiplex optical information and to enhance a storage density of holographic optical information.

Experimental implementation of multiplexing/demultiplexing in digital images using virtual phase conjugation for holographic data storage

Abstract: We experimentally implemented and proved the concept of multiplexing and demultiplexing in digital images using virtual phase conjugation, which was proposed in our previous study. In the experiment, we concluded that two digital images multiplexed in a single signal beam are recorded in a holographic medium, and these images are independently and successfully reproduced. In this method, the digital images are multiplexed by superimposing them on a complex amplitude, and not using volume hologram’s multiplexing. Thus, the exposure amount in the holographic medium is constant regardless of the number of multiplexing of digital images, and the method has great potential for achieving high recording density.

Apparatus for amplifying a signal

Abstract: Apparatus for amplifying a signal beam having a normalised intensity distribution (Figure 2) comprises, an optical waveguide with a core 30, and a first cladding 10 surrounding core. There is at least one pump beam source configured to supply optical pumping. The gain medium 20 is configured to be pumped by the optical beam, and the gain medium 20 is situated in a region of the optical waveguide where the intensity of signal beam is smaller than its peak intensity. The apparatus is configured to have an effective area ratio of between one and 10. The gain medium 20 may be doped with Ytterbium to produce an amplified wavelength in the range from 950 nm to 1050 nm. The gain medium 20 may be doped with erbium to produce an amplified wavelength in the range from 1450 nm to 1600 nm. The gain medium 20 may be doped with Nd to produce an amplified wavelength in the range 850 nm to 950 nm. The first cladding 10 which may guide the optical pump beam can be surrounded by a second cladding 210 having a lower refractive index in the first cladding.

Crystal orientation dependence of the SNR for signal beam amplification in photorefractive BaTiO3

Abstract: In signal beam amplification by two-beam coupling in BaTiO 3 photorefractive crystals, beam fanning in the direction of the amplified signal reduces the signal-to-noise ratio (SNR). The dependence of the SNR and the signal beam gain on the crystal orientation are analysed using a HeNe laser. It is found that orientating the crystal for maximum gain gives poor signal-to-noise ratio. A compromise has to be made between the SNR and high gain for optimum signal amplification.

Analysis of Phase Multilevel Recording on Microholograms

Abstract: An optical phase multilevel recording technique using a microholographic system and phase-diversity homodyne detection for enhancement of optical disc capacity is investigated. In this technique, multilevel phase signals are stored as the fringe shifts along the optical axis and recovered from the arctangent of two homodyne-detected signals. For comparison, phase signals from Blu-ray Disc read-only memory (BD-ROM) and Blu-ray Disc recordable (BD-R) media obtained by phase-diversity homodyne detection are experimentally evaluated. From the experimental results, we demonstrated that phase-diversity homodyne detection is useful for detecting the phase signal modulation of the signal beam from an optical disc. Furthermore, simulation results on microholograms indicate that phase signals from the microholograms are much more stable despite the variety of their sizes than those from BD-ROM. These results demonstrate the potential of this multilevel recording method.