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Nowadays, state-of-the-art for optical data storage (ODS) have emerged as a leader in the competition of data storage technologies. However, the development of optical storage technology based on optically stimulated luminescence (OSL) encounter the serious problems, of single storage mode and easily decoding. In this study, a series of Ba 2 SiO 4 (denoted as BS): Eu2+, Ln3+ (Ln = Dy, Ho) phosphors with adjustable trap distributions (trap depths of 0.6–0.8 eV) have been developed by high-temperature solid-phase method and exhibit intense green emission peak located at 504 nm under excitation of 360 nm. Typically, BS: 0.02Eu2+, 0.02Ho3+ phosphor owns a shallow trap depth of 0.696 eV and BS: 0.02Eu2+, 0.02Dy3+ phosphor shows a deep trap depth of 0.81 eV. Interestingly, the flexible optical information storage film prepared by BS: 0.02Eu2+, 0.02Ho3+ phosphor through spin-coating technique can storage the "National Water Conservation Logo" pattern under NUV irradiation and reappear even after more than 60 days at 75 °C. Subsequently, multimodal anti-counterfeiting strategy is proposed by BS: Eu2+, Ln3+ (Ln = Dy, Ho) phosphors with adjustable trap depths and the flexible information coding device with high transmittance has been developed, in which encrypted message of "HELLO" and "86068" can be recognized at 75 °C and 130 °C, respectively. This work not only lays the foundation for realizing the durability of optical information storage, but also provides high security with multiple levels of retrievability. [ABSTRACT FROM AUTHOR]

Alkaline earth stannate is characterized by good physicochemical stability. It has been applied in the field of optical information storage by coupling photoluminescence intensity modulation and photochromic performance, which has attracted the attention of researchers. The development of alkaline earth stannate ceramics with high light intensity modulation properties and non-destructive reading of optical information is of great research value. In this study, Er3+-doped Ca 2 SnO 4 photochromic ceramics were prepared by high-temperature solid-phase reaction method. Alternating UV light irradiation and thermal stimulation, the ceramics achieve a reversible transition between light and dark gray. Er3+ doping gives the ceramics dual-mode luminescence light intensity modulation performance. When the doping amount of Er3+ is 0.01 mol, there is a maximum down-conversion luminous intensity modulation ratio of 93%, which is higher than most of the same type of photochromic materials. The photochromic behavior is explained using the capture-release model of traps for carriers, and the dual-mode luminescence light-intensity modulation behavior is analyzed through the energy transfer mechanism. The optical radiation response properties were investigated and the optimum light response wavelength is found to be 290 nm, which is related to the optical band gap E g. And the selection of the optimal light response wavelength can effectively improve the performance of photochromic and light intensity modulation. This study provides a promising strategy for performance enhancement of photochromic materials. [ABSTRACT FROM AUTHOR]

The big data era demands an efficient and permanent data storage technology with the capacity of PB to EB scale. Optical data storage (ODS) offers a good candidate for long-lifetime storage, as the developing far-field super-resolution nanoscale writing technology improves its capacity to the PB scale. However, methods to efficiently read out this intensive ODS data are still lacking. In this paper, we demonstrate a sub-diffraction readout method based on polarization modulation, which experimentally achieves the sub-diffraction readout on Disperse Red 13 thin film with a resolution of 500 nm, exceeding the diffraction limit by 1.2 times (NA = 0.5). Differing from conventional binary encoding, we propose a specific polarization encoding method that enhances the capacity of ODS by 1.5 times. In the simulation, our method provides an optical data storage readout resolution of 150 nm, potentially to 70 nm, equivalent to 1.1 PB in a DVD-sized disk. This sub-diffraction readout method has great potential as a powerful readout tool for next-generation optical data storage. [ABSTRACT FROM AUTHOR]

In the current data age, the fundamental research related to optical applications has been rapidly developed. Countless new-born materials equipped with distinct optical properties have been widely explored, exhibiting tremendous values in practical applications. The optical data storage technique is one of the most significant topics of the optical applications, which is considered as the prominent solution for conquering the challenge of the explosive increase in mass data, to achieve the long-life, low-energy, and super high-capacity data storage. On this basis, our review outlines the representative reports for mainly introducing the functional systems based on the newly established materials applied in the optical storage field. According to the material categories, the representative functional systems are divided into rare-earth doped nanoparticles, graphene, and diarylethene. In terms of the difference of structural features and delicate properties among the three materials, the application in optical storage is comprehensively illustrated in the review. Meanwhile, the potential opportunities and critical challenges of optical storage are also discussed in detail. [ABSTRACT FROM AUTHOR]

Optical data storage (ODS) materials have attracted much attention due to their unparalleled advantages, including outstanding low cost, high speed, and high storage density. The dynamic readout of high-resolution optical information in a single medium has always been a hotspot in the design of ODS materials. This work successfully developed a multi-mode dynamic luminescent material LiGaO 2. By adjusting the defect states in different synthetic atmospheres, LiGaO 2 materials with different luminescence properties were obtained, it appears green glow in air and nitrogen atmospheres and orange-red glow in reductive atmospheres. LiGaO 2 material synthesized in a reduction atmosphere (R–LiGaO 2) not only has the characteristics of rapid filling, but also has more abundant trap distribution, so it has a good optical information storage capacity, which is very suitable for the field of ODS. Through the analysis and characterization of R–LiGaO 2 material in thermally-stimulated luminescence (TSL) and photostimulated luminescence (PSL), it is found that the dynamic optical information readout based on intensity-color-wavelength multiplexing in undoped single ODS materials is realized through the synergistic effect of trap centers and luminescence centers. This work provides a new strategy for the design and application of ODS materials. [ABSTRACT FROM AUTHOR]

Photon-mode ultracapacity storage media made of inorganic photochromic luminescent materials are highly anticipated, and widely explored in the development of new optical data storage (ODS) technologies. Despite some recent breakthroughs, the optical storage capacity of defect-rich photochromics is still limited to low luminescent readout abilities. Herein, oxygen vacancy rich and bismuth doped K 0.5 Na 0.5 NbO 3 :Eu3+ ceramics were designed, and synergistically boost the luminescence intensity, photochromic efficiency, and luminescent modulation properties, then effectively improving the luminescence readout abilities. The luminescence modulation ratio reaches up to 97.5% from 68.4% with the increase of oxygen vacancy concentrations due to hetero-valent bismuth doping, accompanied by high photochromic efficiency (35.7% from 21.9%) and excellent reproducibility. These results demonstrate that the synergistic engineering of oxygen vacancy and doping is a promising strategy for obtaining high-performance photochromic materials. [ABSTRACT FROM AUTHOR]

Long-term optical data storage (ODS) technology is essential to break the bottleneck of high energy consumption for information storage in the current era of big data. Here, ODS with an ultralong lifetime of 2×107 years is attained with single ultrafast laser pulse induced reduction of Eu3+ ions and tailoring of optical properties inside the Eu-doped aluminosilicate glasses. We demonstrate that the induced local modifications in the glass can stand against the temperature of up to 970 K and strong ultraviolet light irradiation with the power density of 100 kW/cm2. Furthermore, the active ions of Eu2+ exhibit strong and broadband emission with the full width at half maximum reaching 190 nm, and the photoluminescence (PL) is flexibly tunable in the whole visible region by regulating the alkaline earth metal ions in the glasses. The developed technology and materials will be of great significance in photonic applications such as long-term ODS.

The big data era demands an efficient and permanent data storage technology with the capacity of PB to EB scale. Optical data storage (ODS) offers a good candidate for long-lifetime storage, as the developing far-field super-resolution nanoscale writing technology improves its capacity to the PB scale. However, methods to efficiently read out this intensive ODS data are still lacking. In this paper, we demonstrate a sub-diffraction readout method based on polarization modulation, which experimentally achieves the sub-diffraction readout on Disperse Red 13 thin film with a resolution of 500 nm, exceeding the diffraction limit by 1.2 times (NA = 0.5). Differing from conventional binary encoding, we propose a specific polarization encoding method that enhances the capacity of ODS by 1.5 times. In the simulation, our method provides an optical data storage readout resolution of 150 nm, potentially to 70 nm, equivalent to 1.1 PB in a DVD-sized disk. This sub-diffraction readout method has great potential as a powerful readout tool for next-generation optical data storage.

In the current data age, the fundamental research related to optical applications has been rapidly developed. Countless new-born materials equipped with distinct optical properties have been widely explored, exhibiting tremendous values in practical applications. The optical data storage technique is one of the most significant topics of the optical applications, which is considered as the prominent solution for conquering the challenge of the explosive increase in mass data, to achieve the long-life, low-energy, and super high-capacity data storage. On this basis, our review outlines the representative reports for mainly introducing the functional systems based on the newly established materials applied in the optical storage field. According to the material categories, the representative functional systems are divided into rare-earth doped nanoparticles, graphene, and diarylethene. In terms of the difference of structural features and delicate properties among the three materials, the application in optical storage is comprehensively illustrated in the review. Meanwhile, the potential opportunities and critical challenges of optical storage are also discussed in detail.

The information burst in modern society poses new challenges to information preservation technology, both in storage efficiency, capacity, and security. Multi‐dimensional optical data storage based on the femtosecond laser direct writing technique is a promising way to face these challenges. Herein, a new optical storage method based on femtosecond laser‐induced local darkening of CdSe quantum dots doped glass is reported. Photoluminescence image and spectrum indicate that highly luminescent well‐crystallized CdSe quantum dots can be amorphized by a single femtosecond laser pulse and reconstructed by thermal treatment, resulting in reversible luminescence modulation, in which the luminous efficacy of CdSe quantum dots in glass matrix was well recovered after each cycle of writing and erasing. Complicated patterns written inside the glass and multi‐layer information are also successfully inscribed and well demonstrated. Data bit could be written by just one 380 fs single pulse with pulse energy as low as 100 nJ. The present work provides a potential way for three‐dimensional optical information storage and data encryption with low power consumption, fast writing speed, large capacity, and high security. [ABSTRACT FROM AUTHOR]

Storage capacity of a conventional optical disc can be enhanced significantly by recording data within the three-dimensional volume. However, spherical aberrations and light-scattering limit the number of layers that can be efficiently recorded and retrieved. In this paper, we show that by optimizing the multi-layer data recording and reading parameters, the number of fabricated layers could be tripled to 60 in commercial grade poly-methyl-methacrylate polycarbonate and reduce the read laser power by a factor of 7 by the 20th layer. Influence of spherical aberration on write laser spot size was studied by using vector diffraction theory and compared with experimental values obtained by monitoring the threshold energy of the write laser with depth. Scattering losses of the read laser were studied by simulating the propagation of light through multi-layered micro-structured material. The main advantage of our technique is its practical implementation, as it refrains from the use of index-matching liquids and specialized optics during the read–write process. [ABSTRACT FROM AUTHOR]

Encoding information in light polarization is of great importance in facilitating optical data storage (ODS) for information security and data storage capacity escalation. However, despite recent advances in nanophotonic techniques vastly enhancing the feasibility of applying polarization channels, the data fidelity in reconstructed bits has been constrained by severe crosstalks occurring between varied polarization angles during data recording and reading process, which gravely hindered the utilization of this technique in practice. In this paper, we demonstrate an ultra-low crosstalk polarization-encoding multilayer ODS technique for high-fidelity data recording and retrieving by utilizing a nanofibre-based nanocomposite film involving highly aligned gold nanorods (GNRs). With parallelizing the gold nanorods in the recording medium, the information carrier configuration minimizes miswriting and misreading possibilities for information input and output, respectively, compared with its randomly self-assembled counterparts. The enhanced data accuracy has significantly improved the bit recall fidelity that is quantified by a correlation coefficient higher than 0.99. It is anticipated that the demonstrated technique can facilitate the development of multiplexing ODS for a greener future.

In this paper, the inscription of polarization‐sensitive birefringent structures of two types by femtosecond laser pulses is described. Depending on the laser beam parameters, the orientation of the slow axis of birefringent structures can be either parallel or perpendicular to the polarization of the laser beam. The dependence of retardance and slow axis of birefringence on laser exposure parameters is revealed. The thermal stability of both types of structures is examined. The possibility of highly secure data storage based on the different thermal behavior of the laser‐modified region is demonstrated. [ABSTRACT FROM AUTHOR]

Storage capacity of a conventional optical disc can be enhanced significantly by recording data within the three-dimensional volume. However, spherical aberrations and light-scattering limit the number of layers that can be efficiently recorded and retrieved. In this paper, we show that by optimizing the multi-layer data recording and reading parameters, the number of fabricated layers could be tripled to 60 in commercial grade poly-methyl-methacrylate polycarbonate and reduce the read laser power by a factor of 7 by the 20th layer. Influence of spherical aberration on write laser spot size was studied by using vector diffraction theory and compared with experimental values obtained by monitoring the threshold energy of the write laser with depth. Scattering losses of the read laser were studied by simulating the propagation of light through multi-layered micro-structured material. The main advantage of our technique is its practical implementation, as it refrains from the use of index-matching liquids and specialized optics during the read–write process.

Newly long afterglow phosphor-in-glass (PiG) plays pivotal roles in the region of optical data storage. By using solid-phase reactions and unique spectrum modulation methods, a color-tunable PiG with decent persistent phosphorescence which can be tuned from green to blue has been fabricated. Lu 3 Al 2 Ga 3 O 12 : Ce3+, Cr3+ (LuAGG: Ce3+, Cr3+) based on TBZNA glass could emit bright green light signal located at 350 and 420 nm ascribed to the 5d 1 /5d 2 -4f transitions when corresponding optical data was being loadout. The doping of Cr3+ increases the density of the trap and provides additional traps between the shallow trap and the deep trap to capture more electrons, further improving afterglow decay time. And the storage time and cyclic reading times are derived by the method of thermal stimulation. Thereinto, tunable emission color has been obtained via changing the concentration of Ga3+, using UV excitation. Moreover, the influence of the Cr3+/Ga3+ on luminescence properties of long-afterglow-PiG materials have been described in detail. Achieved results confirm that it makes LuAGG-PiG as a long afterglow PiG matrix, demonstrating its promising application in optical data storage. [ABSTRACT FROM AUTHOR]

We investigate and report on the kinematics of photoisomerization processes of polymer composite thin films based on azo dye methyl red (MR) hosted in polymethylmethacrylate (PMMA) incorporated with Benzyl dimethyl ketal (BDK) as a photo-initiator. Understanding photoisomerization mechanisms is crucial for several optical applications such as Read/Write/Erase (WRE) optical data storage media, UV light Read/Write heads, and UV light sensors. The as-prepared polymer composite thin films are characterized using UV–Vis spectroscopy. Furthermore, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) are employed to investigate the optical, chemical, and morphological properties of trans- and cis-states of PMMA-BDK-MR polymer composite thin films. The presence of the azo dye MR in the composite is essential for the efficient performance of the cis ↔ trans cycles through illumination ↔ thermal relaxation for Write/Read/Erase optical data storage and UV-light sensors. Moreover, UV–Vis and FTIR results confirm the hysteresis cycle of trans- and cis-states and that PMMA-BDK-MR thin films may be regarded as potential candidates for successful Write/Read/Erase optical data storage and UV-light sensors. In addition, the morphology of the thin film surface is investigated by SEM technique. The SEM images indicate that uncured surfaces of PMMA-BDK-MR thin films are inhomogeneous compared with the corresponding surfaces after curing. The transformation from inhomogeneous surfaces to homogeneous surfaces is attributed to the polymerization of thin films by UV curing.

In this paper, shift multiplex recording of phase data pages on a volume polarization-sensitive medium by retardagraphy is demonstrated. The origin of shift selectivity in volume retardagraphy is explained. In the experiment, four-valued phase data pages are used. Then, a coding method is proposed to correct a reconstructed phase pattern. The recorded phase data pages are reconstructed using the feature of the coding method. By comparing the reconstructed phase data pages with recording phase data pages, symbol error rates of less than 11% are achieved. From the experimental result, it is verified that volume retardagraphy is applicable to optical memory.

A new physical insight into the ultrafast information communication can be gained from the reversible and robust petahertz (PHz, 10 ^15 Hz) current induced by a strong few-cycle optical waveform in large band-gap dielectrics. We explore an asymmetric conduction of the petahertz current using a heterojunction of low-hole-mass and low-electron-mass dielectrics and devise various functionalities enabling the petahertz signal processing, like diode, switch, and diode transistor. We then propose a model of one-bit optical nonvolatile random-access memory (RAM) by assembling those functionalities and demonstrate its petahertz operation. Further, we suggest the scalability up to a four-bit data manipulation based on the 2 × 2 array of four one-bit RAM elements.

Optical data storage was performed with various thin polymer films containing coumarin-based derivatives and by using femtosecond laser pulses as well as two-photon absorption processes. Exploring the photodimerization attribute of coumarin derivatives and using appropriate irradiation wavelengths, recording/erasing processes could be carried out in the same area. Second harmonic generation microscopy was used to read the stored information. [ABSTRACT FROM AUTHOR]

Optical data storage was performed with various thin polymer films containing coumarin-based derivatives and by using femtosecond laser pulses as well as two-photon absorption processes. Exploring the photodimerization attribute of coumarin derivatives and using appropriate irradiation wavelengths, recording/erasing processes could be carried out in the same area. Second harmonic generation microscopy was used to read the stored information.

We describe an encrypted communication principle that forms a secure link between two parties without electronically saving either of their keys. Instead, random cryptographic bits are kept safe within the unique mesoscopic randomness of two volumetric scattering materials. We demonstrate how a shared set of patterned optical probes can generate 10 gigabits of statistically verified randomness between a pair of unique 2 mm3 scattering objects. This shared randomness is used to facilitate information-theoretically secure communication following a modified one-time pad protocol. Benefits of volumetric physical storage over electronic memory include the inability to probe, duplicate or selectively reset any bits without fundamentally altering the entire key space. Our ability to securely couple the randomness contained within two unique physical objects can extend to strengthen hardware required by a variety of cryptographic protocols, which is currently a critically weak link in the security pipeline of our increasingly mobile communication culture. [ABSTRACT FROM AUTHOR]

Nature offers exciting examples for functional wetting properties based on superhydrophobicity, such as the self-cleaning surfaces on plant leaves and trapped air on immersed insect surfaces allowing underwater breathing. They inspire biomimetic approaches in science and technology. Superhydrophobicity relies on the Cassie wetting state where air is trapped within the surface topography. Pressure can trigger an irreversible transition from the Cassie state to the Wenzel state with no trapped air--this transition is usually detrimental for nonwetting functionality and is to be avoided. Here we present a new type of reversible, localized and instantaneous transition between two Cassie wetting states, enabled by two-level (dual-scale) topography of a superhydrophobic surface, that allows writing, erasing, rewriting and storing of optically displayed information in plastrons related to different length scales. [ABSTRACT FROM AUTHOR]

In recent years, there have been many research studies focusing on next generation optical data storage technologies, such as near-field recording and holographic data storage systems. Many studies from several disciplines have been perfoed and merged to realize of the next generation optical data storage. The technologies that have been developed for optical data storage are also essential for the other research areas. These technologies can be widely applied to various fields, such as near-field optics-based microscopy, small-sized imaging systems, plasmonic nanolithography using a solid immersion lens (SIL) and a nanoscale aperture, and bio-applications. In this paper, the applications and concepts of the next generation of optical storage technologies are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The recent discovery of photoconvertible and photoswitchable fluorescent proteins (PCFPs and RSFPs, respectively) that can undergo photoinduced changes of their absorption/emission spectra opened new research possibilities in subdiffraction microscopy and optical data storage. Here we demonstrate the proof-of-principle for read only and rewritable data storage both in 2D and 3D, using PCFPs and RSFPs. The irreversible burning of information was achieved by photoconverting from green to red defined areas in a layer of the PCFP Kaede. Data were also written and erased several times in layers of the photochromic fluorescent protein Dronpa. Using IrisFP, which combines the properties of PCFPs and RSFPs, we performed the first encoding of data in four colours using only one type of fluorescent protein. Finally, three-dimensional optical data storage was demonstrated using three mutants of EosFP (d1EosFP, mEosFP and IrisFP) in their crystalline form. Two-photon excitation allowed the precise addressing of regions of interest (ROIs) within the three-dimensional crystalline matrix without excitation of out-of-focus optical planes. Hence, this contribution highlights several data storage schemes based on the remarkable properties of PCFPs/RSFPs. [Copyright &y& Elsevier]

We designed a superparaboloidal solid immersion mirror (SP-SIM) using a tilted parabolic mirror that applied total internal reflection to an optical flying head for near-field recording. As an SP-SIM does not need an objective lens or folding mirror, the height and weight of the optical flying head can be reduced. Using theoretical ray tracing, we found the optimal parameters for rotational symmetric beam intensity on a high-numerical-aperture (NA) focus. The effective NA of the SP-SIM was 132 for both the sagittal and meridional focuses. A 408-nm laser source and high refractive index material, NbFD13, was used for the simulation. The minimum spot sizes at full width l/e2 intensity were 237 and 232 nm in the sagittal and meridional directions, respectively, at normal incidence. The size of the beam spot was kept nearly uniform within a maximum 5% deviation as the field angle changed within ±0.15°. The SP-SIM measured 0.83 mm x 0.95 mm x 0.27 mm (W x L x H) and weighed ca. 0.6 mg. [ABSTRACT FROM AUTHOR]

A novel sol-gel processing route has been developed for the production of tellurium oxide (TeO2) and tellurium suboxide (TeO x) thin films. The process has been used to deposit thin films on glass substrates by the dip coating process. These films have been shown to undergo thermally induced, reversible changes in optical properties on heating at appropriate temperatures. Formation of TeO x was found to occur at low temperatures by direct breakdown of the sol-gel derived material even in the absence of reducing agents whilst the principal optical effects corresponded to the formation of TeO x and α-TeO2 at temperatures of <200°C and <450°C respectively. The relatively low temperatures required to induce significant optical effects are comparable with conventionally prepared TeO x and offer the potential application of these materials in optical data storage systems. [ABSTRACT FROM AUTHOR]

Yellow-emitting optical data storage phenomena were observed in a series of Ca 2 BO 3 Cl: Eu2+, Ln3+ (Ln = La, Ce, Pr, Sm, Gd, Tb, Ho, Tm, Yb, Lu) long-persistent phosphors. Eu2+ in Ca 2 BO 3 Cl could emit yellow light located at 580 nm ascribed to the 5d-4f transitions when optical data was being read out. As co-activators, Ln3+ had various effects in causing afterglow and changing trap concentration. Optical data storage phenomena occurred for each combination of Eu2+ and Ln3+ in calcium borate chloride host. Thereinto, prepared Ca 2 BO 3 Cl: Eu2+, Ce3+ phosphor presented a decent afterglow and optical storage property. Its afterglow decay time was more than 1 h at room temperature and had a bright yellow optical signal at 473 K Ca 2 BO 3 Cl: Eu2+, Ho3+ showed an optimum optical storage property, which remained bright yellow light even after 7 days of data storage. This outstanding optical data storage performance was mainly derived from Ho3+ increased the trap concentration of oxygen vacancies. The crystal structure, excitation and emission spectra, afterglow decay curves and thermoluminescence curves were measured and analyzed in all Eu2+ and Ln3+ doped Ca 2 BO 3 Cl samples. A simple optical data storage method was set up and effective optical signals were observed. Based on these results, detailed optical data storage processes and possible mechanism were studied and discussed. • Ca 2 BO 3 Cl: Eu2+, Ln3+ phosphors had a common deep trap at ∼473 K, which could just be used for optical data storage. • An excellent yellow-emitting optical data storage phenomenon was observed in this series long-persistent materials. • Thermoluminescence curves were studied to explain the optical data storage phenomenon, mechanism and processes. [ABSTRACT FROM AUTHOR]

We investigate and report on the kinematics of photoisomerization processes of polymer composite thin films based on azo dye methyl red (MR) hosted in polymethylmethacrylate (PMMA) incorporated with Benzyl dimethyl ketal (BDK) as a photo-initiator. Understanding photoisomerization mechanisms is crucial for several optical applications such as Read/Write/Erase (WRE) optical data storage media, UV light Read/Write heads, and UV light sensors. The as-prepared polymer composite thin films are characterized using UV–Vis spectroscopy. Furthermore, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) are employed to investigate the optical, chemical, and morphological properties of trans- and cis-states of PMMA-BDK-MR polymer composite thin films. The presence of the azo dye MR in the composite is essential for the efficient performance of the cis ↔ trans cycles through illumination ↔ thermal relaxation for Write/Read/Erase optical data storage and UV-light sensors. Moreover, UV–Vis and FTIR results confirm the hysteresis cycle of trans- and cis-states and that PMMA-BDK-MR thin films may be regarded as potential candidates for successful Write/Read/Erase optical data storage and UV-light sensors. In addition, the morphology of the thin film surface is investigated by SEM technique. The SEM images indicate that uncured surfaces of PMMA-BDK-MR thin films are inhomogeneous compared with the corresponding surfaces after curing. The transformation from inhomogeneous surfaces to homogeneous surfaces is attributed to the polymerization of thin films by UV curing. [ABSTRACT FROM AUTHOR]

We introduce partial-response maximum-likelihood (PRML) signal process to increase the accuracy of reading multilevel signal from a multilevel run-length-limited (ML-RLL) recorded disc. The reason is that the traditional slicer detection is no longer suitable for detecting ML-RLL signal. In this paper, we also present several partial-response methods and their corresponding maximum a likelihood sequential estimation (MLSE) rules for ML-RLL modulation signal detecting. [ABSTRACT FROM AUTHOR]