Optical Storage Applications Research Articles

Detuned surface plasmon resonance scattering of gold nanorods for continuous wave multilayered optical recording and readout

In a multilayered structure of absorptive optical recording media, continuous-wave laser operation is highly disadvantageous due to heavy beam extinction. For a gold nanorod based recording medium, the narrow surface plasmon resonance (SPR) profile of gold nanorods enables the variation of extinction through mulilayers by a simple detuning of the readout wavelength from the SPR peak. The level of signal extinction through the layers can then be greatly reduced, resulting more efficient readout at deeper layers. The scattering signal strength may be decreased at the detuned wavelength, but balancing these two factors results an optimal scattering peak wavelength that is specific to each layer. In this paper, we propose to use detuned SPR scattering from gold nanorods as a new mechanism for continuous-wave readout scheme on gold nanorod based multilayered optical storage. Using this detuned scattering method, readout using continuous-wave laser is demonstrated on a 16 layer optical recording medium doped with heavily distributed, randomly oriented gold nanorods. Compared to SPR on-resonant readout, this method reduced the required readout power more than one order of magnitude, with only 60 nm detuning from SPR peak. The proposed method will be highly beneficial to multilayered optical storage applications as well as applications using a continuous medium doped heavily with plasmonic nanoparticles.

Efficient Synthesis and Photochromic Properties of a New Diarylethene Bearing a Condensed Aromatics Moiety

A new class of diarylethenes based on a hybrid structure of thiophene and naphthalene has been developed and its properties including photochromism, kinetics and fluorescence were investigated in detail. The results showed that the compound exhibited obvious photochromism, changing from colorless to red after irradiation with 297 nm UV light both in solution and in PMMA film. The kinetic experiments indicated that the cyclization/cycloreversion process of the compound was determined to be the zeroth/first order reaction in hexane solution. At last, the results demonstrated that the diarylethene compound had attractive properties for potential application in optical storage.

The luminescence properties of a novel electron trapped material Sr2SnO4:Sb3+ for optical storage

A novel electron trapped material Sr2SnO4:Sb3+ for optical storage is successfully obtained by conventional solid state method at 1300℃ It indicates that the 1S0 1P1 (208 nm) and 1S0 3P1 (265 nm) transitions of Sb3+ are the most efficient writing light source. Its emission covers 400700 nm and can be attributed to 3P0,1 1S0 transition of Sb3+. We can observe yellowish white light and its color coordination is (0.341, 0.395). The thermoluminescence of Sr2SnO4:Sb3+ contains four peaks at about 39 ℃, 124 ℃, 193 ℃ and 310 ℃, respectively. The intensity of peak at 39 ℃ is low and thus it has a weak afterglow which can last only 140 s. However, even after putting it in dark for 1 day, the peak at 310 ℃ can still keep 45.6% of its original intensity and can be efficiently stimulated by 980 nm infrared laser. As a conclusion, the Sr2SnO4:Sb3+ is a promising electron trapping material for application in optical storage.

Efficient Synthesis and Photochromic Properties of a New Diarylethene Bearing a Condensed Aromatics Moiety

A new class of diarylethenes based on a hybrid structure of thiophene and naphthalene has been developed and its properties including photochromism, kinetics and fluorescence were investigated in detail. The results showed that the compound exhibited obvious photochromism, changing from colorless to red after irradiation with 297 nm UV light both in solution and in PMMA film. The kinetic experiments indicated that the cyclization/cycloreversion process of the compound was determined to be the zeroth/first order reaction in hexane solution. At last, the results demonstrated that the diarylethene compound had attractive properties for potential application in optical storage.

Photoinduced write-once read-many-times memory device based on DNA biopolymer nanocomposite

We demonstrate a photoinduced write-once read-many-times (WORM) organic memory device based on DNA biopolymer nanocomposite. The device consists of a single biopolymer layer sandwiched between electrodes, in which electrical bistability is activated by in situ formation of silver nanoparticles embedded in biopolymer upon light irradiation. The device exhibits a switching effect to high conductivity above a threshold of 2.6 V and a good retention property. This facile technique, taking advantage of DNA’s affinity for metals and solution processing, can optically manipulate the properties of DNA nanocomposite thin films, which holds promise for optical storage and plasmonic applications.

Synthesis of a Novel Photochromic Diarylethene and its Application in Optical Recording Storage

A novel unsymmetrical photochromic diarylethene compound bearing dithiol-pentane unit, 1-[2-methyl-5-(1,3-dithiol-pentane)-3-thienyl]-2-[2-methyl-3-benzofuran-yl]perfluoroyclopentene(1a) has been synthesized, and its photochromic, fluorescence and optical recording strorage properties were investigated. The compound exhibited remarkable photochromism and clear fluorescent switches both in solution and in PMMA film. Using diarylethene 1b/PMMA film as recording medium and a linearly polarized 650 nm laser diode for recording and readout, polarization multiplexed image recording can be carried out in this film. The results demonstrated that the diarylethene can be potentially used as polarization multiplexing holographic recording medium.

Optically active methacrylic copolymers with side-chain azoaromatic and 9-phenylcarbazole moieties

The synthesis and structural characterization of optically active copolymers such as poly[( S)-(+)- MCPP- co-( S)- MAP- N] and poly[( S)-(+)- MCPP- co-( S)- MAP- C] has been performed in order to obtain a multifunctional photonic material for chiroptical switches and for optical storage applications. The observed chiroptical properties suggest the presence of ordered chiral conformations at least for the chain segments of the macromolecules. Spectroscopic, thermal and chiroptical characterization of these copolymers demonstrate the occurrence of significant electronic interactions between the carbazole chromophores and the azobenzene moieties. The photoinduction of birefringence of copolymer films has been investigated in order to evaluate their behavior as a material for optical data storage. Surface-relief gratings (SRG) have also been inscribed on the material. The results are interpreted in terms of copolymer composition, cooperative behavior and conformational stiffness of the chromophoric co-units.

Synthesis and Spectral Properties of Triazine-Based Dendritic Dithienylethenes

Two novel triazine-based dendrimers comprising a dithienylethene core and eight and 16 ethyl groups around the periphery were synthesised in high yields in a convergent way, without using tedious protection and chromatographic separation steps. Their optical properties such as photochromism, fluorescence emission and film-forming behaviour were investigated. The new symmetrical dendritic dithienylethenes showed typical photochromic behaviour in solution and good film-forming performance in a poly(methyl methacrylate) (PMMA) matrix. Moreover, the dendrimers have demonstrated remarkable fluorescence enhancement and good solubility in common organic solvents, compared with the corresponding small molecule diarylethene. Thus, the new dendrimers as optoelectronic materials, have potential applications in optical storage, photo-switches, and so on.

A new diarylethene and its application in optical storage

A new blue photochromic diarylethene compound, 1-[5-(3-methoxyphenyl)-2-methyl-3-thienyl]-2-[5-(3-cyanophenyl)-2-methyl-3-thienyl]perfluoroclopentene (1a), was synthesized and its photochemical properties were investigated in detail. The measurement results demonstrated that the compound has good photochromism in solution and in PMMA amorphous film, fluorescence and optical storage properties.

Synthesis and Application for polarization Optical Storage of a New Photochromic compound

A new photochromic compound 1-[2-methyl-5-(4-methyl-phenyl)-3-thienyl]-2-[2-methyl-5-(4-fluor-phenyl)-3-thienyl]perfluoroyclopentene (1a) was synthesized, its photochromic properties were examined, the result indicated that the color of the compound 1a changed from colorless to a blue one upon irradiation with 297 nm UV light, a new absorption maxima were observed at 577 and 581 nm in hexane and PMMA film, respectively. This new photochromic compound also exhibited remarkable optical storage character.

Up-Conversion Photostimulated Luminescence of Mg2SnO4 for Optical Storage

We report the first observation of up-conversion photostimulated luminescence in non-doped Mg2SnO4. Stimulated by 980 nm infrared laser (reading) after ultraviolet irradiation (writing), the phosphor shows photostimulated emission band covering 470–550 nm, which is due to the recombination of F centers with holes. After ceasing ultraviolet irradiation, the storage intensity would rapidly decrease to 59% of its original storage intensity in 2.5 h and then would not degrade anymore. It is suggested that the Mg2SnO4 has potential applications for optical storage. Accordingly, the possible photostimulated luminescence mechanisms of Mg2SnO4 are proposed.

Aggregation and Photoresponsive Behavior of Polyelectrolyte

A novel polyelectrolyte (PLJY) was synthesized based on the azobenzene chromophore containing functional groups (-C=C-) and α-methacrylic acid by radical polymerization. The PLJY was characterized by FT-IR and UV-vis spectroscopy. The thermal property was characterized using the differential scanning calorimeter (DSC). The glass transition temperatures (Tg) was 179.1 oC and showed that the PLJY had excellent thermal stability. Influences of pH values on the UV-Vis absorption spectra of PLJY were studied and polyelectrolyte solution had good pH-sensitivity and H-aggregation behavior. The photoresponsive and thermochromism behaviors were investigated for the azo polyelectrolyte PLJY solution or film. By 256 nm excitation wavelength, the PLJY solution or film appeared photo responsive behavior. At high temperature, the PLJY solution had thermochromic behavior. These results showed that the polyelectrolyte had potential applications in optical information storage and optical switch.

Fabrication of quasi-periodic micro-voids in fused silica by single femtosecond laser pulse

We demonstrate that quasi-periodic void structure can be self-formed in transparent materials by single femtosecond laser pulse. Compared to the multiple-pulse induced structures, the single-pulse induced void structures are very short and may contain absent voids. The formation mechanisms have been discussed comparatively in detail. Based on this, a technique for high-speed and large-area fabrication of micro-void arrays in transparent materials has been presented. The experimental results show that 3D micro-void structures which contain over several hundred thousand voids in micrometer scales are produced in areas of square millimeters within a few minutes, and the periods of micro-void structures can be easily varied by processing parameters. This work has potential applications in 3D optical storage, photonic crystal and integrated optics, and provides novel insight into the interaction between the single femtosecond pulse and the transparent materials.

Spectroscopic ellipsometric study of the optical properties of Ag2O film prepared by direct-current magnetron reactive sputtering

The Ag2O film, as-deposited by direct-current magnetron reactive sputtering at a substrate temperature of 150 °C, clearly shows a preferential orientation (111), and is capable of lowering the threshold value of the thermal decomposition temperature to about 200 °C, which is helpful to its application in optical and magneto-optical storage. This paper fits its optical constants in terms of a general oscillator model by using measured ellipsometric parameters. The fitted oscillator energy 2.487 eV is close to the optical direct interband transition energy value of the Ag2O film determined by Tauc equation; whereas, the fitted oscillator energy 4.249 eV is far from the fitted plasma oscillator energy 4.756 eV by single-oscillator energy. The photoluminescence spectrum centred at about 2.31 eV indicates a direct-energy gap photoluminescence mechanism of the Ag2O film.

A novel photoactive hyperbranched poly(aryl ether ketone) with azobenzene end groups for optical storage applications

A novel hyperbranched poly(aryl ether ketone) terminated by azobenzene chromophores (azo-HPAEK) was prepared using 1,3,5-tris[4-(4-fluorobenzoyl)phenoxy] benzene (B 3) as a core molecule, 4,4′-(hexafluoroisopropylidene) diphenol as an A 2 monomer and 4-(4-hydroxyphenylazo) benzonitrile as an end-capping reagent. It is shown that azo-HPAEK exhibits a high glass transition temperature (Tg), excellent thermal stability and homogeneous photochromic behavior. By exposing the spin-coated film to a laser beam interference pattern, azo-HPAEK can be used for rapid (within 30 s) fabrication of surface relief gratings (SRGs), and the azo-HPAEK gratings cannot be totally erased by heating, even at 300 °C. In particular, azo-HPAEK shows a large photoinduced birefringence intensity and good reversible optical storage upon irradiation with 532 nm Nd:YAG laser.

Optical Switch Formation in Antimony Super-Resolution Mask Layers Induced by Picosecond Laser Pulses

Sb is a classic material of a super-resolution near field structure (super-RENS) mask layer in which the optical switch formation is often realized by nanosecond laser pulse stimulation. We achieve fast and repeatable optical switching driven by picosecond laser pulses in a proper fluence range on Sb thin films. The optical properties of Sb thin films before and after switching are studied by surface-sensitive micro-area ellipsometry. The change of optical constants after switching is less than 2% in the whole visible range. The Sb mask layer is shown to be very promising for ultrafast super-resolution optical storage applications.

Study of reflection gratings recorded in polyvinyl alcohol/acrylamide-based photopolymer

High-spatial-frequency fringes associated with reflection holographic optical elements are difficult to obtain with currently available recording materials. In this work, holographic reflection gratings were stored in a polyvinyl alcohol/acrylamide photopolymer. This material is formed of acrylamide photopolymer, which is considered interesting material for optical storage applications such as holographic memories. The experimental procedure for examining the high-spatial-frequency response of this material is explained, and the experimental results obtained are presented. With the aim of obtaining the best results, the performance of different material compositions is compared.

Synthesis of Carbazole derivatives with Two-photon absorption via Solid-state method and Optical storage application

Synthesis of Carbazole derivatives with Two-photon absorption via Solid-state method and Optical storage application

Feasibility study of the application of radially polarized illumination to solid immersion lens-based near-field optics

We analyzed the behavior of the electric field in a focal plane consisting of a solid immersion lens (SIL), an air gap, and a measurement sample for radially polarized illumination in SIL-based near-field optics with an annular aperture. The analysis was based on the Debye diffraction integral and multiple beam interference. For SIL-based near-field optics whose NA is higher than unity, radially polarized light generates a smaller beam spot on the bottom surface of a SIL than circularly polarized light; however, the beam spot on the measurement sample is broadened with a more dominant transverse electric field. By introducing an annular aperture technique, it is possible to decrease the effects of the transverse electric field, and therefore the size of the beam spot on the measurement sample can be small. This analysis could have various applications in near-field optical storage, near-field microscopy, lithography at ultrahigh resolution, and other applications that use SILs for high resolution.

A miniature spindle motor with fluid dynamic bearings for portable storage device applications

This paper presents the design and fabrication of a miniature axial-gap spindle motor for small-form-factor optical storage applications. The motor features a fluid dynamic bearing (FDB) and is characterized by a high mechanical rigidity, excellent dynamic characteristics, and a zero cogging torque. The performance of this FDB motor is evaluated experimentally using a laboratory-built prototype. The results show that the motor has an excellent dynamic response, a small axial repeatable runout, a small tilt angle, a high rotational speed, and a low operating current. Furthermore, with overall dimensions of just 15.5 × 3.3 mm, the FDB motor is around 80% smaller than that presented by the current group in a previous study (Liu et al., J Magn Magn Mater 304:362–364, 2006). Consequently, the proposed motor represents an ideal solution for both existing and emerging miniaturized portable storage device applications.