The relationship between playback laser power and bit error increase caused by continuous playback is considered. In the Te system write-once media, bit errors increase gradually due to the phase chage of media. Playback laser power should be designed so as media temperature is not overly increased. In TbFe system magneto-optical recording media, bit errors don't increase when playback laser power is lower than threshold recording power.

Theoretical and experimental results are presented for angle-multiplexed and wavelength-multiplexed holographic recording. The recording medium is a cerium doped Sr1-XBaXNb2O6 (SBN) single crystal, and the light sources are a laser diode excited second harmonic generation (SHG) laser and a tunable laser diode. The SBN single crystal has high recording sensitivity, high diffraction efficiency and high temperature stability. The laser diodes miniaturize the holographic recording system. Crosstalk between hologram pages is theoretically calculated by using modified coupled-wave equations, and is also experimentally measured. The experimental results agree well with the theoretical results. Two-dimensional alphabetical character images are recorded using angle- and wavelength-multiplexed holographic methods, and are successfully reconstructed. The theoretical results indicate that several hundred multiplexed holograms can be recorded with little crosstalk using the proposed system. This multiplexed holographic recording technique will enable high-density recording and high data-transfer rates.

In this paper, a linear array of 4 leaf-shaped bowtie slot antennas is proposed for use in quasi-millimeter wave band. The slot antennas array is designed to operate at 28GHz frequency band. The leaf-shaped bowtie slot antenna is a type of self-complementary antenna with low profile and low cost of fabrication. The proposed antenna structure offers improvement in radiation pattern, gain, and -10dB impedance bandwidth. Through out of this paper radiation pattern, actual gain, and -10dB impedance bandwidth are evaluated by Finite Different Time Domain (FDTD) simulation. Antenna characteristics are analyzed in the frequency range of 27GHz to 29GHz. To improve antenna characteristics such as actual gain and -10dB impedance bandwidth, a dielectric superstrate layer with relative permittivity of 10.2 is placed on top of ground plane of the slot antennas array. Three antenna structures are introduced and compared. With two layers of dielectric superstrate on top of the antennas ground plane, analysis results show that -10dB impedance bandwidth occupies the frequency range of 27.17GHz to 28.39GHz. Therefore, the operational impedance bandwidth is 1.22GHz. Maximum actual gain of the slot antennas array with two dielectric superstrate layers is 20.49dBi and -3dB gain bandwidth occupies the frequency range of 27.02GHz to 28.57GHz. To validate the analysis results, prototype of the designed slot antennas array is fabricated. Characteristics of the slot antennas array are measured and compared with the analysis results.

Holographic data storage (HDS) is a next-generation optical storage that uses the principles of holography. The multiplex holographic recording method is an important factor that affects the recording capacity of this storage. Various multiplex recording methods have been proposed so far. In this study, we focus on shift multiplexing with spherical waves and propose a method of shift multiplex recording that combines the in-plane direction and thickness direction of the recording medium. In conventional shift multiplexing with spherical waves, shift multiplexing is usually carried out with respect to the direction parallel to the plane of the recording medium. By focusing on the fact that shift selectivity is also in the thickness direction, we examined the possibility of a multiplex recording method that combines multiple shift directions. Simulation and experimental verification shows that the proposed method is effective in principle.

Recently, a lot of UWB antennas have been reported by many research groups. Most of the reported antennas have omnidirectional radiation characteristics. The disadvantage of using omnidirectional antennas is that the antenna performance can be degraded by adjacent walls or metals. If unidirectional UWB antennas are utilized, the degradation on the antenna performance due to omnidirectionality can be avoided. Another important topic in UWB antennas is the waveform distortion caused by antennas' transmission characteristics. In impulse-based UWB communications, waveform distortions of transmitted and received pulses caused by antennas deteriorate the communication performance. Therefore, the development of UWB antennas having small waveform distortions is highly desirable. In this paper, we propose a novel bowtie antenna using leaf-shaped radiating elements and a flat reflector. This antenna has unidirectional radiation patterns over the frequency range of 3.0 to 10.5 GHz. The actual gain in the maximum radiation direction is 6.0-9.0 dBi in the frequency range of 4.5-9.4 GHz (relative bandwidth of 71%). The cross-correlations between source pulse and received pulse waveforms are 0.89-0.94, and hence the waveform distortion caused by this antenna is relatively small. As a result, the proposed antenna is useful for impulse-based UWB communication systems using correlation detection.

An image NRD guide-fed dielectric rod antenna, which is suitable for use at millimeter-wave frequencies, is presented in this paper. The antenna is composed of a linearly tapered dielectric rod connected to the image NRD guide. First, radiation characteristics of the dielectric rod antenna directly protruded from the end of the image NRD guide are investigated by FDTD analysis and measurements at 30 GHz band. For this case, the degradation of the radiation pattern and the decrease of the gain, which are due to the strong radiation from the guide-to-antenna discontinuity, are observed. In order to minimize this radiation and to realize reasonable radiation characteristics, a transition from the image NRD guide-to-rod antenna is proposed. A simple procedure to determine the optimum dimensions of the transition is described. This procedure is based on parametric study of the transition's dimensions, and is performed using FDTD analysis. Based on the results, the dielectric rod antenna having a length of 10 λ0 is designed, and its performance is analyzed and measured. The results show that radiation patterns with the half power beamwidth of 22, sidelobe level of -21 dB and reasonable gain of 18.5 dBi can be realized by employing the transition having the optimum dimensions.

In this paper, we presented a computer simulation analysis of high-density hologram recording, which is a promising mass optical memory technique. A simulation method for off-axis speckle-shift multiplexed recording by three-dimensional computer simulation analysis was presented, as well the signal evaluation of recording and reproduction. By this simulation method, the characteristic features of recording and reproduction are studied from the viewpoints of signal-to-noise-ratio and the reproduced image's quality, and a high-density speckle-shift multiplexed recording condition is proposed.

The optical recording of video signals in real-time and in a high band color mode has been achieved using diode lasers whose light pulse duration is emphasized according to the RF frequency.