We have studied two-photon absorption (TPA) recording in photochromic diarylethenes for a three-dimensional (3D) optical memory, and demonstrated the TPA recording for the first time using a laser diode with a pulse width of 2 ns without a thermal influence. In comparison with the recording sensitivity by a femtosecond fiber laser, it was found that the peak power can be greatly reduced and the TPA sensitivity has squared characteristics depending on the pulse width range from 94 fs to 2 ns. Finite difference time domain (FDTD) analysis of optical intensity through refractive pits suggests that 3D recording in multilayered medium is more suitable, because optical aberrations induced by the lens effect of refractive pits are greatly reduced and the reflectance from a pit is improved, in comparison with that in a bulk medium.
The relationship between the size of films in a dry foam and the size of the bubbles is investigated. The study was carried out using foam structures simulated using Surface Evolver, with the structures covering a wide range of poly-dispersities. It was found that the most important factor influencing the size of a film is the size of the smaller bubble to which it is attached. The larger bubble does have an influence, but it is much smaller, with the film size increasing by approximately 80% as the larger bubble goes from the same size as the smaller bubble to infinitely large. The relationship between a film's size and the size of the two bubbles to which it is attached was found to be independent of the underlying bubble size distribution, with the probability distribution for the size of the film depending only on the size of the neighbouring bubbles.
The use of CD-ROM has become widespread. PC users have generally been satisfied with the performance CD-ROM's, however, there is also a demand for larger-capacity removable rewritable media for “Multimedia” applications. The “PD” system offers users an optical disk which is easily handled such as floppy disks presently in use. In addition, “PD” can also read CD-ROM at fourtimes of the speed using a single common slot for both CD-ROM and PD media. The PD system (name of the new optical disk system prososed by Matsushita Electric Industrial. Co., Ltd.) has good compatibility for pit and groove recording. We calculated the reflectivity, tracking error, and ROM modulation, and varied the groove depth and width to maximize performance. A signal was written on various pregroove depths, and the reproduced signal ratio was measured. We obtained good results by using a phase-change material with the PD optical disk.
Diffraction ef~:ciencies of a reflection-type blazed holographic optical element (HOE) are analyzed and optimized L0r use in a totally integrated optical head. The HOE, consisting of four-step phase levels, was fabricated by a double-etching process. By controlling each etching depth, signal light power efficiency was maximized to 16% and the power ratio of noise components relative to signal light power was suppressed to 21%. Diffraction efiiciencies were made uniform over the entire HOE in oblique positioning by controlling the respective step widths of the HOE.
A very small holographic optical pick-up head with a movable single-assembly optical system was proposed. The optical system measures 11 mm(W)×4 mm(D)×4 mm(H) and weighs only 0.34 grams. The basic performance of the optical system mounted on a conventional actuator was demonstrated experimentally.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.