KEYWORDS: Optical transfer functions, Confocal microscopy, Sensors, Optical storage, Objectives, 3D modeling, Point spread functions, Diffraction, Luminescence, Data storage
A quasi-vector diffraction simulation tool is introduced to simulate a fluorescent bit-wise volumetric optical data storage system. Examples and a comparison of simulation results with an analytical optical transfer function calculation are presented.
We report playback performance results of volumetric optical data storage disks that are made from a new class of light-absorbing (photo-chromic) compounds. The disks are first exposed to a simulated space environment. In order to simulate the space environment, a vacuum oven bakes the disks for certain amount of time at a designated temperature. Test results in this temperature study are fit into an Arrhenius model. Disks are also exposed to radiation doses similar to those found in a space environment. Disks fail in high temperature and large proton-dose conditions. Heavy ions do not cause significant disks failure. The prevention of disk failure due to harsh space environments is also discussed.
A new dynamic test stand is built to test coupon samples for volumetric bit wise optical data storage applications. An unconventional rotating head and fixed sample design is employed. Results from media samples are reported that illustrate pulse-length/power optimization and focus sensitivity. One sample is shown to be appropriate for volumetric applications based in its focus sensitivity.
We describe a new mounting technique for rapid alignment using semi-kinematic (SK) rails. Features of the technique include structures for positioning lens elements, beam splitters, mirrors, and the like. The SK rails are less complicated to machine than traditional v-groove technology.
KEYWORDS: Finite-difference time-domain method, Near field optics, Dielectrics, Optical recording, Near field scanning optical microscopy, Near field, 3D modeling, Glasses, Diffraction, Laser scattering
The data density of the optical recording medium depends on the focused beam spot size, which is limited by diffraction. Near-field optical techniques using evanescent light have been developed to overcome the diffraction limit of the far-field optics. In particular, Betzig et al. have applied a scanning near-field optical microscope (SNOM) for magneto-optical recording. The resolution of the metal coated tapered SNOM probe is limited by the aperture size and not by the farfield diffraction limit. A resolution less than 60nm was demonstrated. However, low efficiency of the throughput of this probe limits the speed of read-out and recording. In other research, Terris et al. have developed near-field optical recording optics using the solid immersion lens (SIL). The advantage of SIL is a high optical throughput which is larger than that of conventional SNOM probe. However, there is technical difficulty in keeping the position of the relatively large flat bottom of the SIL in the near-field of the recording medium. Recently, Ghislain et al. developed a tapered SIL whose bottom is a sharp conical shape to improve the positioning of the SIL probe. We designed an alternative tapered probe whose bottom is flat, table shaped and 1/n wavelength in diameter. This diameter is large enough to propagate the incident light without significant decay of the amplitude. This probe shape also can be easily made by using a conventional lithography technique and can be applied to the flying—head for nearfield optical recording. The probe shapes and optical configurations are schematically illustrated in Fig.l. In this study, we employed three dimensional (3D) FDTD model to compute the electromagnetic field of this probe optics. A full-vector computation method of electromagnetic field, which based on the Maxwell’s equations, is necessary to design a practical near-field probe. Arbitrary probe shapes and geometries can be modeled using the 3D-FDTD method.
KEYWORDS: Optical recording, Objectives, Refractive index, Near field scanning optical microscopy, Near field optics, Head, Glasses, Liquids, Diffraction, Semiconductor lasers
The data density ofthe optical recording medium depends on the focused beam spot size, which is limited by diffraction. The beam spot size can be reduced by using a shorter wavelength light source or a larger NA objective lens. Recently, near-field optical techniques using evanescent light, have been developed to overcome the diffraction limit of far-field optics.
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