Optical Storage Systems Research Articles

Adaptive Regulation of Tracking Servo for Next Generation Optical Data Storage Systems

The tracking servo control has played an important role in the data storage servo systems. In the next generation optical data storage systems, i.e. the near-field recording system, the tracking error of the servo system should be below 10 nanometers under various unknown situations. However, higher data transfer rate and higher data density make it difficult to maintain the desired tracking precision during normal disk operation. It is proposed in this paper to use an adaptive regulation approach to maintain the tracking error below its desired value, despite unknown track eccentricity and external force disturbance. The performance of the proposed control approach is analyzed and simulation results are presented to illustrate the capability of the proposed adaptive regulator to achieve and maintain the desired tracking precision.

Two-Photon Three-Dimensional Optical Storage of a New Photobleaching Material

Two-photon three-dimensional optical data storage is an important method to realize high density storage and ultra-high density storage. This paper introduces the the basic principle of two-photon photobleaching optical storage, describes two-photon three-dimensional optical storage system and the absorption and fluorescence spectra of a new type of photobleaching materials BASF in detail, carries out the experimental study that two-photon information is written and read out against a new photobleaching material of BASF using femtosecond pulse laser wavelength is 800nm, and realize two layers of optical information storage, the information point spacing is 8μm and the interlayer distance is 15μm; two-layer information point signal strength is recognized using Recognition algorithm. The experiment proved that new photobleaching material of BASF can be used for two-photon three-dimensional optical storage, that has laid a solid foundation for the high-density and ultra-high density optical information storage materials research.

Optimizing the optical field distribution of near-field SIL optical storage system using five-zone binary phase filters

Five-zone binary phase filters (FBPFs) are proposed for decreasing the spot size and/or increasing the focal depth of the near-field optical storage system with a hemisphere solid immersion lens (SIL). The design of filters is based on the vector diffraction theory and the MATLAB optimizing toolbox. Three FBPFs with rotationally symmetrical pupil function have been designed, where the one FBPF is for increasing the focal depth as big as possible, the second FBPF is for improving the resolution as high as possible, and the third FBPF integrate the increase of focal depth with the improvement of resolution. Numerical results show that compared with the three-zone amplitude filter, the designed five-zone binary phase-only filters have more prominent performances in improving the focal depth and the resolution of the near-field SIL optical storage system.

On frequency response and stability of an optical front–end with variable‐gain current amplifier using a bipolar junction transistor translinear loop

ABSTRACTA comparative analysis of implementations of an optical front–end with variable transimpedance intended for optical storage systems in two different BiCMOS technologies is given in this article. The variable‐gain current amplifier within the optical front–end is designed by using a modified balanced type of the bipolar junction transistors translinear loop. The predictions of the optical front–end mathematical models are confirmed by the measured results. They show that a 0.6‐µm BiCMOS silicon technology implementation with worse bipolar junction transistor parameters (unity‐gain frequency, current gain β, and the Early voltage) gives much better stability than a 0.35‐µm BiCMOS silicon‐germanium technology implementation. As a consequence, the useful measured transimpedance dynamic range of the proposed optical front–end is 17.5 times larger in the 0.6‐µm BiCMOS silicon technology than that in the 0.35‐µm BiCMOS silicon‐germanium technology. Copyright © 2012 John Wiley & Sons, Ltd.

Focusing Error Detection Method in Microholographic Data Storage System Using Polarization Characteristics

We present a disk-focusing error detection method for microholographic data storage systems using polarization characteristics. In high-speed optical storage systems, disturbances exist along the vertical direction of a disk. The diffraction efficiency of a readout signal depends on the distance between the focusing point of the reference beam and the vertical center of the microholographic grating. The proposed disk focusing error detection method uses only one laser source, unlike most existing systems, which use two laser sources. By using polarization characteristics, disk-focusing and reading beams are inserted in the media without interference, and the proposed system achieves the simultaneous reading of microholograms and disk-focusing control. By evaluating the focus error signal, we verified the reliability of the optical path and tolerable S-curve (FES) balance (1.8%) for the proposed system. It is possible to achieve a diffraction efficiency of over 90% at the best focus position using the proposed disk-focusing method.

The Hardware and Software Design of Dual Pick-up Head Three-Dimensional Optical Storage System

Femtosecond laser two-photon three-dimensional optical data storage is an effective method for high capacity data storage. In this paper, system construction is analyzed in detail from hardware and software aspects for dual pick-up head three-dimensional optical storage systems. Three-dimensional optical storage system is conposed of the fluorescence reader module and the servo control module, firstly analyzes the read and write process of three-dimensional optical storage by 89c52 MCU controling from the hardware. Then, the software is analyzed in detail, the software consists of two parts: the lower computer software and PC software. lower computer software achieves communication and control related to hardware, PC software is used to facilitate the control of the experimental system. Two CPU control software is introduced, and controlling process of PC software control is analyzed in detail. These work has laid a solid foundation for the practical of three-dimensional optical storage technology.

From Spheric to Aspheric Solid Polymer Lenses: A Review

This paper presents a new approach in the use of MEMS technology to fabricate micro-optofluidic polymer solid lenses in order to achieve the desired profile, focal length, numerical aperture, and spot size. The resulting polymer solid lenses can be applied in optical data storage systems, imaging systems, and automated optical inspection systems. In order to meet the various needs of different applications, polymer solid lenses may have a spherical or aspherical shape. The method of fabricating polymer solid lenses is different from methods used to fabricate tunable lenses with variable focal length or needing an external control system to change the lens geometry. The current trend in polymer solid lenses is toward the fabrication of microlenses with a high numerical aperture, small clear aperture (<2 mm), and high transmittance. In this paper we focus on the use of thermal energy and electrostatic force in shaping the lens profile, including both spherical and aspherical lenses. In addition, the paper discusses how to fabricate a lens with a high numerical aperture of 0.6 using MEMS and also compares the optical characteristics of polymer lens materials, including SU-8, Norland Optical Adhesive (NOA), and cyclic olefin copolymer (COC). Finally, new concepts and applications related to micro-optofluidic lenses and polymer materials are also discussed.

Resolution-limited optical recording in 3D

We present an optical write/read system for high density optical data storage in 3-D. The microholographic approach relies on submicron-sized reflection gratings that encode the digital data. As in conventional optical data storage, the physical limitations are imposed by both the diffraction of light and resolution of the recording material. We demonstrate resolution-limited volume recording in photopolymer materials sensitive in the green and violet spectral range. The volume occupied by a micrograting scales down by the transition in the write/read wavelength. Readout yields a micrograting width of 306 nm at 532 nm and 197 nm at 405 nm. To our knowledge these are the smallest volume holograms ever recorded. The recordings demonstrate the potential of the technique for volumetric optical structuring, data storage and encryption.

Research on the Application of DVD Pick-Up Head in Three-Dimensional Optical Storage

Two-photon three-dimensional optical data storage is an effective method for high capacity data storage. Based on DVD pick-up head and two-photon absorption, two-photon three-dimensional optical disk storage system is built, and operating principle of the overall system is in detail. In the servo module of three-dimensional optical disk storage system, DVD circuit control board (MT1389SE) is conducted on three-point improvement: extract focus servo error signal and servo error signal, increase four communications interfaces，increase photoelectric detectors; the extraction of focus and track servo signal on reading and writing module is analyzed in detailed. The measured principles and methods of the voice coil motor characteristic curve of Sanyo DVD pick-up head (SF-HD60S) are analyzed in detailed by using dual-frequency laser interferometer, which can be well meet the layer selection requirements of three-dimensional optical storage. DVD pick-up head applied in three-dimensional optical storage overcomes the limitations of three-dimensional scanning stage, integrates with existing DVD servo technology, and lays a solid foundation for practical use of two-photon three-dimensional optical storage.

Plasmonic nanofocusing of light in an integrated silicon photonics platform

The capability to focus electromagnetic energy at the nanoscale plays an important role in nanoscinece and nanotechnology. It allows enhancing light matter interactions at the nanoscale with applications related to nonlinear optics, light emission and light detection. It may also be used for enhancing resolution in microscopy, lithography and optical storage systems. Hereby we propose and experimentally demonstrate the nanoscale focusing of surface plasmons by constructing an integrated plasmonic/photonic on chip nanofocusing device in silicon platform. The device was tested directly by measuring the optical intensity along it using a near-field microscope. We found an order of magnitude enhancement of the intensity at the tip's apex. The spot size is estimated to be 50 nm. The demonstrated device may be used as a building block for "lab on a chip" systems and for enhancing light matter interactions at the apex of the tip.

Improving longitudinal shifting selectivity of volume holographic optical elements by introducing a light pipe

We propose a new scheme to enhance the longitudinal Bragg selectivity of a volume hologram with use of a light pipe. Longitudinal shifting selectivity of the system is shown to be obviously enhanced in both experimental measurement and theoretical calculation. Such a technique is not only useful in the volume holographic 3-D imaging but also useful in the shift multiplexing holographic optical storage system.

A 78.4 dB Photo-Sensitivity Dynamic Range, 285 T$\Omega$Hz Transimpedance Bandwidth Product BiCMOS Optical Sensor for Optical Storage Systems

An optical sensor with variable transimpedance for optical storage systems in 0.6 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\hbox {m}}$</tex> </formula> BiCMOS technology is presented. A PIN photodiode, a voltage-controlled current amplifier, and a current-to-voltage converter are monolithically integrated. A balanced type of the BJT translinear loop based voltage-controlled current amplifier is used. A linearity error smaller than 3.6%, a transimpedance dynamic range of 8323 (78.4 dB) with the largest transimpedance of 12.9 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${\hbox{M}}\Omega$</tex></formula> , a maximum photo-sensitivity of 6824 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\hbox{mV}}/\mu{\hbox {W}}$</tex></formula> at 675 nm, an offset voltage below 2.2 mV, a maximum power consumption of 9.1 mW, a bandwidth up to 463 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$~$</tex></formula> MHz, a transimpedance bandwidth product up to 285 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\hbox {T}}\Omega{\hbox {Hz}}$</tex></formula> , and an output noise power down to <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$-$</tex></formula> 72.5 dBm (at 50 MHz and a resolution bandwidth of 30 kHz) are achieved.

Two‐Photon 3D Optical Data Storage via Aggregate Switching of Excimer‐Forming Dyes

A novel optical data storage (ODS) system that relies on the optically-induced switching of the aggregation state and fluorescence of a two-photon absorption dye in a polymer matrix is reported. Well-defined, ∼3 × 3 × 6 μm large voxels are written with single focused laser pulses and read by confocal laser scanning microscopy.

Dynamic Recording of 200 Gbytes in Three-Dimensional Optical Disk by a 405 nm Wavelength Picosecond Laser

We present experimental results of our volumetric optical data storage system. To achieve volumetric recording over a wide depth range of 250 µm in a recording medium, we developed a relay lens system for compensating for the spherical aberration of a high-numerical-aperture (0.85) objective lens. The disk employs a single monolithic recording layer and a reference layer for servo control. A 405-nm-wavelength titanium:sapphire laser that exhibits 2 ps pulse duration and a more than 2 kW peak power is used for recording. We adopted void formation and mark position as recording principles. We have experimentally demonstrated 34-layer dynamic recording, corresponding to a capacity of 200 Gbytes.

Nonlinear Modeling for Super-RENS Disc Using a Simplicial Canonical Piecewise-Linear Adaptive Filter

A correct and accurate model of an optical storage system is very important in the development and performance evaluation of various data detection algorithms. In this paper, we present a nonlinear modeling of a super-resolution near-field structure (super-RENS) read-out signal using the simplicial canonical piecewise-linear (SCPWL) model. The validity of this model is tested using radio frequency (RF) signal samples obtained from a super-RENS disc. The experiment results on modeling indicate that the SCPWL model can be efficiently utilized for the nonlinear modeling of the super-RENS systems.

A Survey of Control Issues in Optical Data Storage Systems

AbstractThis paper presents a survey of control issues in optical storage data systems. Servo control has the important role of moving the optical pick to a track and regulating it to read and write data along the track. The performance of the servo system determines total system performance, such as access time, data rate, and latency. In this regard, we review servo control systems and walk readers through key issues of servo control technology. We also discuss servo control issues in some new storage technologies, such as near-field recording systems. Although optical data storage systems are highly precise mechatronic systems, they have not yet been considered extensively in the literature of the control engineering society. This review provides a description of servo control issues in optical data storage systems from specification to implementation of control theory. We thus believe that this paper will be useful for readers practicing control theory both in academia and in industry.

The glass-molding process for planar-integrated micro-optical component

This paper presents a precision glass-molding process to fabricate planar-integrated micro-optical components (PIMOC) applied to a micro projection display system, optical interconnection system and optical storage system. The PIMOC was designed based on wave propagation theory, and fabricated using a glass molding process. Experimental results are discussed in this article. The experiment showed that the PIMOC fabricated in a vacuum environment meets the design value with precision glass-molding technology (PGMT) at a molding force of 2.75 kN, a molding temperature of 750 °C and a cooling rate of 49 °C/min.

A BJT translinear loop based optoelectronic integrated circuit with variable transimpedance for optical storage systems

A 0.35 μm SiGe BiCMOS optical receiver with voltage-controlled transimpedance is presented. A variable-gain current amplifier using a BJT translinear loop is applied. A transimpedance dynamic range of 1554 (63.8 dB) with the largest transimpedance of 2.84 M?, a bandwidth up to 379 MHz, and a transimpedance bandwidth product up to 168 T?Hz are achieved.

A two-dimensional constant-weight sparse modulation code for volume holographic data storage

In order to simplify the threshold determination, reduce the inter-pixel cross-talk, and improve the storage density for high-density volume holographic data storage, a two-dimensional constant-weight sparse modulation code is proposed. The evaluation criteria and design rules are investigated based on the page-oriented optical data storage system. Coding parameters are optimized to achieve large channel capacities. An 8:16 modulation code is designed to reduce the raw bit error rate and its performances are experimentally evaluated. A raw bit error rate of the magnitude of 10−4 is obtained with a single-data-page storage and 10−3 with multiplexing.

Synthesis, thermal and optical properties of metal(II) complexes with a novel ligand derived from pyrazolone-5

Three novel metal(II) complexes, CoL2, NiL2 and CuL2 (L = (Z)-4-(2-(1,3-dimethyl-5-oxo-1H-pyrazol-4(5H)-ylidene)hydrazinyl)-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one were synthesized. Their structures were postulated based on elemental analyses, 1H NMR, ESI-MS, FT-IR spectra and UV-vis spectra. The effect of different central metal(II) ions on absorption bands of the metal(II) complexes in CHCl3 solutions was researched. The result indicates that the bathochromic shift is CuL2 > NiL2 > CoL2. The absorption properties of thin films and thermal stability of these complexes are also discussed. In addition, the optical constants (complex refractive index N=n+ik) and thickness of the complex thin films on polished single-crystal silicon substrates were measured by spectroscopic ellipsometry. Results indicate that the metal(II) complexes would be a promising recording medium candidate for blu-ray recordable optical storage system due to good absorption at 405 nm, high thermal stability and sharp thermal decomposition, and a high n values of 1.35–1.45 and a low k values of 0.33–0.39.