In heat assisted magnetic recording, near field optical transducer is a key component for its success. Due to the near field
properties, the transducer design has to be done combining with media. FePt is a potential recording material for heat
assisted recording. In this paper, the measured optical constant of FePt thin film was introduced, and the design and
simulation of c-aperture transducer with FePt media for multiple Tb/in2 heat assisted magnetic recording application
were performed. The light spot sizes of around 15nm with high efficiency were obtained. Optical transducer is used to
heat the media locally. Its final target is to generate smaller thermal profile to meet the requirement of recording density.
Therefore, using obtained beam spot as heat source, thermal simulations were carried out with media material's thermal
parameters. The simulation results show that recording density of 3Tb/in2 is possible.
The current limitation in pixel count of a single spatial light modulator (SLM) is one of the technological hurdles that must be overcome to produce a holographic 3-D display with a large image size. A conventional approach is to tile subholograms that are predivided from a reconfigurable computer-generated hologram (CGH) with a high pixel count. We develop a new approach to achieve a 50 Mpixel display by tiling reconstructed subholograms computed from a predivided 3-D object. The tiling is done using a two-axis scanning mirror device with a new tiling sequence. A shutterless system design is also implemented to enable effective tiling of subholograms. A high-speed digital micromirror device (DMD) at 6 kHz with 1920×1080 pixels is utilized to reconstruct the subholograms. Our current system shows the potential to tile up to 120 subholograms, which corresponds to about 240 Mpixels. The approach we demonstrate gives a scalable solution to achieve a gigapixel-level display in the future.
In this paper the focusing effect of flat metallic-slit array in micro-meter scale area is discussed and the role of
surface plasmons waves inside slits is recognized. A proximate relationship between the equivalent focal length
and slit material, slit geometrical parameters is built. The theoretically derived focal length and that from Finite
Difference Time Domain (FDTD) simulation is proved to be in good agreement. Additionally, FWHM of focal
point, focal depth and intensity of focal point for the slit array with invariant slit width and the slit array with
variant slit width are compared as well. The slit array with varied slit width is found to have the better
performance than slit array with invariant slit width.
The modeling for investigating the thermal effect on slider in heat assisted magnetic recording is built and its verification
is conducted by comparing the simulation results and experiment results. The temperature distribution on the slider
induced by locally heated media in 1Tb/in2 is simulated and the results show that the effect is within a very small zone
on the bottom surface. The temperature changes on other surfaces are less than 0.1°C, which can be negligible.
Surface plasmon propagation properties for nano-sized metal aperture and nano-wire structures are studied based on the
waveguide theory. It is verified that there are only TM0 and HE1 mode existing in both structures. For nano-wire
structure, however, there is no cut-off radii for both TM0 and HE1 mode. On the contrast, there is a cut-off radius for
nano-sized silver aperture structure, and even more, there are several characteristic radius coefficients a/ λ, -0.32, 0.73.
For each section, the EM wave may takes on different features, e.g., totally-bounded features along the aperture interface
for a/ λ >0.73, or oscillation inside core or strong attenuation along z direction for 0.32<a/ λ<0.73). HE1 mode of metal
aperture doesn't show cut-off radius as well, but the wave-number along z direction monotonically increase with the
radius coefficient a/ λ in contrast with existence of a characteristic radius coefficient a/ λ of 0.41 for nano-wire.
Before reaching the true heat assisted magnetic recording, which is in optical near-field case for high recording density, the component level researches are needed. This requires a platform to support these kinds of researches. In this talk, the platform structure is introduced and its functions of researching on media material and structures, interface, overcoat and lubricant are discussed. Finally, some experimental results are presented.
This paper reviews the past analytical and non-analytical approaches for the Surface Plasmons (SPs) effect, present a simple description to the widely adopted curvilinear coordinate method. Based on the concept of Fourier decomposition of any complicated grating profiles, a comprehensive analysis is given to the contribution of every order components to the overall behavior of the practical zero-order metal gratings. It successfully predicts the energy gap, resonant SPs modes, the red-shift behavior and the broadening effect of energy gap by higher order components. At the same time, it's found that within certain wavelength range of interest, only first several orders of components are needed to be taken into account to predict the behavior of the non-sinusoidal gratings. As an application, this analysis approach is extended to behavior of the triangular gratings. The limitation and possible generalization of this method are also discussed.
The three-dimensional model of the packaging device is established based on ANSYS simulation platform. The thermal properties such as time response, axial and radial temperature distributions at different applied voltages are exhibited. With aids of Real Time Optical Spectrum Analyzing System and IR Camera System, time response of the device and axial temperature distribution along the coated fiber with intracore FBG are both demonstrated. Temperature responses to different applied voltages are achieved after measuring voltage induced wavelength shift and temperature dependent wavelength shift. Simulation shows results in agreement with those of experiment. Finally, regulations on length of the metal coating, size of the package, power consumption and tuning properties of the packaging device are discussed.
Lithium Niobate is an important material in optical communication due to its special characteristics (high electrooptic coefficients and high optical transparency in the near infrared wavelengths). In this paper, we investigated the effects of 775-nm, femtosecond laser radiation on the Lithium Niobate crystal. By focusing the laser beam through a microscope objective, a certain refractive index change may be induced in Lithium Niobate substrate. Based on this effect, channel waveguides and other waveguide structures were fabricated. The output optical fields through them were measured, and the refractive index change of ~6×10-4 was calculated with the Near-field Method. The properties of these waveguide structures were discussed. We also investigated the waveguides effect induced with different fabrication conditions. The experimental results revealed that different fabrication conditions affect the waveguide effect greatly.
The out-radial movements of pickup head in optical data storage systems are studied, and its influences on Push-pull track error signals and Differential Phase Detection (DPD) track error signals are analyzed.
The limitations of the conventional optical storage technology are first analyzed in this paper. The fundamental issues regarding terabytes optical recording are then discussed. Finally, the storage capacity of various approaches is presented.
Recently, the near field recording using a Solid Immersion Lens (SIL) is getting much attention to be a promising candidate of super high density optical recording. The high density recording is achieved by introducing a highindex SIL between the recording medium and the objective lens, thereby increasing the numerical aperture (NA) of the optical system and reducing the focal spot size. The SIL lens is usually a hemisphere or a super-hemisphere. The preliminary analyses of readout signal in this case have been reported.
With the development of high density optical disk storage, the characteristic size of the interaction object is comparable to the wavelength of the light which is used to read/write the disk. In this resonance region, the conventional scalar diffraction theory can not be applied to analyze the system anymore. Vector diffraction theories have been proposed to address this problem: thin film theory for treatment of the multilayer structure of flat surface, rigorous grating theory for treatment of the pre-grooved multilayer coated disk, finite methods for treatment of the pre-grooved multilayer coated disk with the presence of irregular data marks. Among the various finite methods, finite-difference time-domain (FDTD) method can treat the complex disk structure and is relatively easy to implement.5,6* But when treating focusing problem, the incident focusing beam was approximated as Gaussian plane beam previously. This is not the case in high NA optical storage system. In this paper, we propose a three dimensional FDTD method which can be used to analyze the high NA optical disk storage system.
A variety of CD and DVD recordable and rewritable disc formats have or shortly will transition into mass market products. Apart from the inherent manufacturing complexity, this development has created very demanding requirements on unit manufacturing cost, production yields, and quality. The dynamic storage marketplace has placed additional, constantly evolving demands on product capabilities. All of this is reflected in the current approach to optical disc manufacturing equipment through their emphasis on modularity, flexibility, and upgradeability. The developments in the CD-R arena encapsulate and serve to highlight these issues and will be used as a case study.
Near-field optical recording is a potential way to get higher recording density. In this technology, the Solid Immersion Lens is used to increase optical system numerical aperture, thus reduce the focused beam spot.
The development of phase change recording is spurred by the demand of high capacity, low cost and rewritable optical data storage. In phase change optical disk, recording and erasing are achieved by laser heating that induces the crystallographic structural changes in the media. The difference in reflectivities of crystalline and amorphous states determines the information stored. Hence the dependence of optical and thermal effects arising from the laser irradiation on the disk needs to be thoroughly investigated. In today’s competitive marketplace, companies are looking into ways of producing better product at lower cost and shorter development time. Thus the capability of performing interactive computer modeling and analyses of the optical disk becomes inevitable to achieve these ends.
Vibration analysis is an integral part of the design process for precise components, especially for higher density optical disk drives (e.g. DVD ROM/RAM). The designer often encounters challenges arising due to undesirable vibration modes in the components. The demands for precise track accessing and focusing are of importance in higher density optical disk drives. However, structural resonant vibration of mechanical components in the optical pickup head limits the tracking and focusing servo performances. Such tighter design specifications require the designer to have in-depth understanding of how structured resonance of the actuator in the optical pickup head responds to its tracking or focusing mechanism.
The tolerances of Supersphere Solid Immersion Lens (SSIL) system in aberration were analyzed. The maximum deviation between objective lens and SSIL was given in several different optical parameters. The optical coupling efficiency of the SSIL to the air space were also calculated in these cases.
A new thermal model to study the laser induced temperature profile of a multilayered phase change optical recording disk is proposed. The new model considers the thermal effect generated by both the transmission and reflection light. The calculation formulae are listed. The model is used to simulate the Ge2Sb2Te5 phase change optical disks with five layers structure. In order to study the differences between the new and existing models, simulations are carried out using both models and the differences are compared. The differences get larger as the phase change layer becomes thinner. It is also revealed that the differences get larger as the wavelength becomes shorter. The idea proposed in this paper is also suitable for the analysis of magneto-optical disks as well as for improved accuracy in the measurement of thermal parameters.