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Information storage and security are the building blocks of the information age. Optical information storage is a low‐cost, robust, and high‐capacity storage technique. Discovering new optical information storage media and techniques with beyond binary capacity and enhanced security is in demand. Here a beyond‐binary, "burn after read" and rewritable multiplexing optical information storage and encryption method is demonstrated via Ce:YAG trapping states. It is found that the thermo‐luminescence (TL) intensity of Ce:YAG trapping states is writing light power dependent, enabling multi‐gray‐level information storage and encoding.A new strategy to encode multiplexing information in a single pixel, increasing the storage capability is presented. Meanwhile, the burn after read feature protects the data from secondary leakage. This method has wide applications in data storage, anti‐counterfeiting, and encryption. [ABSTRACT FROM AUTHOR]

Luminescent materials are emerging promising tools for digital data encoding due to their reduced cost, facile reading, robustness, and durability. For this, the use of fluorescent systems that combine multicolor emission with sensitivity to external stimuli will be highly desirable, as they can offer rewritable data encoding together with enhanced encryption security and storage density. Herein a novel strategy is pioneered to reach this goal, which exploits the temperature‐responsive emission properties of the mixtures of regular fluorophores with simple organic phase change materials (PCMs) such as paraffins. By preparing a diversity of microcapsules of these mixtures comprising different dyes and PCMs, thermosensitive fluorescent pixels can be prepared in a low‐cost, straightforward, and scalable manner that exhibits multicolor dynamic emission behavior. These features are capitalized to fabricate pixel arrays that perform two advanced digital encoding operations: high‐security 3D information encryption, and 4D data storage. [ABSTRACT FROM AUTHOR]

In ultrafast laser writing, and light‐matter interaction in general, it has been widely accepted that the higher the energy density, the stronger material changes occur, unless thermal effects are involved. Here, this belief is challenged by demonstrating that a decreased energy density—achieved through increased scanning speed and without thermal accumulation—surprisingly leads to a more significant modification of silica glass, i.e, a higher increase in the isotropic refractive index or greater birefringence of nanopore‐mediated modification. This counterintuitive phenomenon is attributed to the nonlocality of light‐matter interaction at tight focusing, where the intensity gradient of the light beam and associated diffusion of charge carriers play a critical role in increasing material modification. A tenfold increase in the writing speed of the polarization multiplexed data storage with the potential to achieve MB s‐1 using high transmission nanopore‐based modification. [ABSTRACT FROM AUTHOR]

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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]

A macrocyclic azobenzene with unique thermal stability, demonstrating potential for use in optical data storage material is presented: The Z‐isomer of this novel photoswitch exhibits unparalleled thermal stability, with a thermal half‐life surpassing 120 years at 25 °C. This stability is attributed to the strategic fluorination at two ortho‐ and both para‐positions. Comparative analyses involving its non‐fluorinated counterpart, ortho‐only‐fluorinated variant, and open‐chain analog are performed. Employing NMR and UV–vis spectroscopy, X‐ray diffraction, alongside Arrhenius, Eyring, and DFT calculations, revealed insights into its extraordinary stability. Furthermore, when incorporated into poly(methylmethacrylate), this material showcase efficient switching with visible light in the solid state, emphasizing its potential for optical data storage applications. [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]

Due to the evolution of data centric applications demand for high speed data transfer and more bandwidth is increasing continuously. The unavailability of components like tunable wavelength converters (TWCs) restrict the transfer of parallel information using wavelength division multiplexing (WDM), therefore in the present scenario optical orthogonal frequency division multiplexing can be used. Moreover in optical communication narrow Gaussian pulses are transmitted, which spread with distance and leads to the broadening of the pulse and pulse peak power goes down and thus limits the system. In this paper a Soliton based optical communication system is proposed and its comparison with Gaussian pulse is presented and it has been found that soliton pulse has lesser bit error rate in comparison to Gaussian pulses. [ABSTRACT FROM AUTHOR]

UV‐charged optical stimulated single‐band phosphors are being used for single‐level optical data storage because of their ability to easily write/read information by light. In contrast, UV–visible–NIR rechargeable optical stimulated double‐band phosphor is urgently necessary for multiplexed high‐throughput optical data storage. Here, the authors design and synthesize Mn2+,Cr3+ co‐doped zinc gallate storage persistent phosphor that exhibits strong red‐green bicolor persistent luminescence (PersL). Besides the traditional ultraviolet charging, the phosphor can be effectively and repeatedly charged by using visible and NIR light by one‐ or two‐photon process. Interestingly, red and green PersL exhibit the opposite temperature dependence, which is extremely important for multilevel information storage. The mechanism of temperature‐dependent PersL intensity based on different trap types and filling approaches for the double luminescence centers is proposed. The phosphor promises a sophisticated application in optical data storage of wavelength multiplexing. [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]

In recent years, inorganic lead halide perovskite quantum dots have been used in various optoelectronic fields for their excellent luminescence properties, such as narrow emission bands, ultra‐wide tunable emission wavelength, and high quantum efficiency. In this paper, different from luminescence optimization in most research, luminescence degradation of perovskite quantum dots is addressed by femtosecond laser irradiation and successfully used for three‐dimensional data storage in CsPbBr3 quantum dots doped glass. Photoluminescence (PL) degradation can be finely modulated by adjusting the laser parameters. PL degradation mechanism, investigated by optical spectroscopy and morphology characterization, is attributed to laser‐induced decomposition, recrystallization, and defection of CsPbBr3 quantum dots. Laser‐induced PL degradation and the followed PL recovery by heat treatment are repeated for several cycles, showing good reversibility. Multilayer PL degradation patterns are written into the glass and read out without crosstalk, indicating high‐reliability 3D optical storage characteristics. Amazingly, PL degradation can be induced by just a low‐energy single laser pulse with estimated subpicosecond writing time per bit, demonstrating its potential in high‐speed, low‐power consumption 3D optical storage. [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.

The demand for energy efficient data storage technologies with high capacity and long life span is increasingly growing due to the explosion of digital information in modern society. Here, a 5D optical data storage with high capacity and ultralong lifetime is realized by femtosecond‐laser‐induced anisotropic nanopore structures (type X modification) in silica glass. The ultrahigh transmission of this birefringent modification, >99% in the visible range, allows recording and retrieving thousands of layers of multibit digital data practically. Type X formation is associated with moderate free carrier density produced close to the energy threshold of avalanche ionization. Higher retardance with increased repetition rate at low pulse energy is attributed to accumulation of defects (nonbridging oxygen hole centers), enabling rapid imprinting of voxels by megahertz‐rate pulses. Data recording of 7 bits per voxel, i.e., 25 azimuth angles and 22 retardance levels is experimentally demonstrated with readout error as small as 0.6%. Furthermore, "The Hitchhiker's Guide to the Galaxy" by Douglas Adams is optically recorded with a data writing speed of 8 kB s−1 in 100 layers of voxels and the proven data readout accuracy of 100%. [ABSTRACT FROM AUTHOR]

Nanofabrication techniques have significantly impelled the development of nanomechanics and nanophotonics by making nano‐precision material processing routine. Although widely employed, current sub‐100 nm nanofabrication approaches based on focused particles or light are limited to surface modification. Here, an optical in‐volume fabrication approach that enables 3D glass processing with a spatial resolution down to 40 nm is demonstrated. Such an approach is based on the formation of a single nanoslit structure induced by femtosecond laser pulses. Spatially‐variant nanopatterns with uniform line‐widths are then formed by a near‐field mediated intensity redistribution of incident light. The redistribution of electromagnetic field induced by the presence of the nanoslit leads to a positive‐feedback self‐assembly process. The self‐assembly process allows achieving spacing one order of magnitude smaller than the laser beam size. In addition, a tilted ablation front that results in the generation of structures with curved morphology is revealed. The proposed approach enables 3D patterning with a lateral spacing down to 200 nm and 5D optical data storage with an equivalent capacity of 7.2 TB per disk, demonstrating its feasibility for 3D nanoscale processing in bulk materials. [ABSTRACT FROM AUTHOR]

The big data era has presented major challenges for data centers worldwide in information preservation aspects, such as storage capacity and long‐term sustainability. Here, a newly synthesized optically active polymeric material based on a highly thermally stable penta‐functional monomer dipentaerythritol pentaacrylate is reported. This material supports ultra‐high storage density with century‐long data lifetime utilizing the galvo‐dithered direct laser writing nanofabrication technique. Eighty layers of bit arrays and 16 grayscale‐level coding examples are demonstrated to confirm the feasibility of the 4D data storage with a data density reaching 10 terabytes per digital video disc. With the much‐improved thermal stability (the data degradation point reaches beyond 600 K) than average plastic materials, such as polymethylmethacrylate, this new polymeric material allows a data lifetime of nearly 250 years at room temperature (300 K), as confirmed by the accelerated aging test. This material offers a suitable storage medium solution for next generation optical data storage centers. [ABSTRACT FROM AUTHOR]

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.

A novel nanocomposite thin films based on azo dye methyl red (MR) hosted in polymethylmethacrylate (PMMA) incorporated with benzyl dimethyl ketal (BDK) as a photo-initiator and doped with 2.5% and 5% of silica NPs are prepared by dip coating technique on fused silica substrates. We investigate the optical, chemical and thermal properties of (PMMA–BDK–MR)/silica NPs nanocomposite thin films by performing UV–Vis spectrometer, Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric analyser (TGA). The purpose of inserting the azo dye MR in the composite is to stimulate the nanocomposite to perform the cis ↔ trans cycles through illumination ↔ thermal relaxation for Write/Read/Erase optical data storage and UV-light sensors. Our UV–Vis and FTIR findings confirm the hysteresis cycle of trans- and cis-states. Consequently, (PMMA–BDK–MR)/silica NPs thin films could be successfully used in Write/Read/Erase optical data storage and UV-light sensors. The TGA measurements show that the weight loss of the nanocomposites is reversibly proportional to the silica NPs concentration indicating the reinforcement of physicochemical bonding density as the concentration of silica NPs is increased. [ABSTRACT FROM AUTHOR]

Tailoring ultrafast light–matter interaction as an enabler to create functional periodic crystalline patterns inside transparent dielectrics is of great scientific and technological significance but remains a tremendous challenge because of plenty of unclarified process details and physical mechanisms. Here, a dynamic process of ultrafast laser‐induced continuous periodic crystallization (CPC) to generate self‐organized crystal arrays (CAs) inside the glass is reported. The crystallite‐seeds induced by ultrafast laser are revealed to offer an auxiliary effect that can initiate and maintain the CPC process, which promises the high‐efficiency writing of CAs. The auxiliary effect originates from photo‐induced defects in the crystallite‐seeds, functions by drastically decreasing the pulse energy threshold for writing CAs, and can be manipulated by tuning the glass compositions and laser parameters. The created CAs are erasable and rewritable, which allows for potential applications in optical information encryption and data storage. This work not only opens up an avenue for creating embedded periodic crystalline patterns with extremely high efficiency but also helps to clarify the dynamics of ultrafast laser nanostructuring inside transparent dielectrics. [ABSTRACT FROM AUTHOR]

Plasmonic color generation utilizing ultrathin metasurfaces as well as metallic nanoparticles holds a great promise for a wide range of applications including color displays, data storage, and information encryption due to its high spatial resolution and mechanical/chemical stability. Most of the recently demonstrated systems generate static colors; however, more advanced applications such as data storage require fast and flexible means to tune the plasmonic colors, while keeping them vibrant and stable. Here, a surface‐relief aluminum metasurface that reflects polarization‐tunable plasmonic colors is designed and experimentally demonstrated. Excitation of localized surface plasmons encodes discrete combinations of the incident and reflected polarized light into diverse colors. A single storage unit, namely a nanopixel, stores multiple‐bit information in the orientation of its constituent nanoantennae, which is conveniently retrived by inspecting the reflected color sequence with two linear polarizers. Owing to the broad color variability and high spatial resolution of the metasurface, the proposed encoding approach holds a strong promise for rapid parallel readout and encryption of high‐density optical data. The method also enables robust generation of dynamic kaleidoscopic images without the "cross‐talk" effect. The approach opens up a new route for advanced dynamic steganography, high‐density parallel‐access optical data storage, and optical information encryption. [ABSTRACT FROM AUTHOR]

Hybrid material of poly-methyle-methacrylate (PMMA)-benzyl-dimethyl-ketal-azo dye methyl red (MR) thin film composites doped by various concentrations of ZnO NPs have been dip coated on glass substrates. The existence of azo dye (MR) in the composite was intentional to give the solution the desired pH level and to induce the cis ↔ trans cycles through illumination ↔ thermal relaxation. The optical and structural properties of the as-prepared thin films are investigated in relevance to ZnO NPs contents and the period of UV light illumination (short- and long-wavelength UV light). We found that the PMMA-BDK-MR doped by 1% ZnO NPs could be successfully used in optical data storage by implementing this composite in the WRITE/READ/ERASE cycle repeatedly. Specifically, it was found that the absorption band of the PMMA-BDK-MR doped by 1% ZnO NPs thin film lies between 350 and 600 nm upon illumination with 366 nm UV light for 10 s. Thermogravimetric analysis (TGA) was used to investigate the thermal stability of PMMA-BDK-MR/ZnO NPs. The TGA results are presented and interpreted. Furthermore, we investigated annealed poly-methyle-methacrylate-benzyl-dimethyl-ketal-methyl-red (PMMA-BDK-MR) doped by 1% ZnO NPs thin films. The trans–cis cycle has been repeated sequentially to confirm the hysteresis behavior for possible data READ/WRITE or ERASE memory applications. [ABSTRACT FROM AUTHOR]

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]

Optically stimulated luminescence (OSL) materials, enabling energy storage by capturing of charge carriers and then the energy conversion to light via photostimulation, can find many advanced applications in various fields, spanning from radiation dosimetry, optical data storage and security, environmental monitoring, biomedicine, clinical diagnostic, to archaeology and geology. At present, there are some blocks, including the development of nanocrystallization approaches, the tailoring of optical transitions, the control of trap distribution, and the understanding of OSL mechanisms, on the road to the exploration of OSL materials. This review gives an overview of the design, preparation, characterization, optimization, application, mechanism, and prospect of OSL materials. A short introduction of the fundamental principle and history of OSL materials is presented, followed by a summary of preparation and design methods, and a survey of OSL materials reported to date. The trap engineering, mechanism, and study methodologies of OSL are summarized, after which the widespread applications of OSL materials, in traditional and newly emerging fields, are reviewed. Finally, the merits and drawbacks of the OSL materials according to the relevant reports currently available are examined. The challenges and outlooks are highlighted and discussed in terms of five important aspects that merit future research. [ABSTRACT FROM AUTHOR]

The need for data storage is growing in modern society, and optical data storage (ODS) is considered one of the most promising storage techniques. However, significant challenges must be overcome, including improving the performance of volatile memory and expanding its storage capacity. In this study, we report a novel ortho-silicate phosphor, BaCaSiO 4 , doped with Eu2+, which exhibits sustained luminescence and optically stimulated luminescence (OSL). Following the Pr3+ co-doping, the long afterglow and OSL performance of BaCaSiO 4 : Eu2+ significantly improved owing to the substantial increase in trap density. Owing to numerous trapped and released electrons, the optical storage capacity of the OSL material significantly increased. As a proof-of-concept, ODS flexible media were fabricated using the obtained OSL material, based on which reversible information write-in and read-out were implemented using ultraviolet irradiation and optical/thermal stimulation, respectively. Furthermore, the OSL-based ODS mechanism was revealed through a comprehensive study of electron trapping, storage, and release kinetics. • A novel long persistent and optically stimulated luminescence phosphor was prepared. • The trap density was significantly increased by 22.71 times through Pr3+ co-doping. • BaCaSiO 4 :Eu2+,Pr3+ flexible membrane was fabricated for reversible optical data storage. • The mechanism of electron dynamics was illuminated in detail. [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.

Laser-induced glass processing has led to huge progress and applications over the last two decades. Here, we review recent advances in femtosecond laser-induced photochemistry in isotropic transparent oxide glasses specifically tailored with silver photoactive agents. The understanding of the influence of the considered glass matrix on the nature and properties of the created silver species is of prime importance. After presenting the key material properties, the formation mechanisms of laser-induced silver-based species are discussed, and potential technological applications are highlighted. Laser-induced processing of silver-containing oxide glasses paved the way for the fabrication of complex integrated waveguides and optical circuits with innovative fluorescent, nonlinear optical, and plasmonic properties. The universality of the method is expected to extend in any glass material that shows a similar laser-induced behavior in terms of silver cluster production. [ABSTRACT FROM AUTHOR]

Abstract: The fast‐growing amount of data that is produced every year creates an urgent need for ultracapacity storage media. However, 2D spatial resolution in the conventional optical data storage media has almost reached the limit. Further enlargement of storage capacity may rely on the development of the next‐generation data storage materials containing multiplexed information dimensions. Herein, a series of novel deep‐trap persistent luminescence materials (Sr1‐xBax)Si2O2N2:Eu/Yb,Dy with multicolor emissions in the whole visible region is developed and demonstrated a bit‐by‐bit optical data storage and readout strategy based on photon trapping and detrapping processes in these materials. Optical data can be handily encoded on a flexible film by a commercially available 405 nm laser and decoded by heating or by 980 nm laser scanning. The decoded information contains tunable spectral characteristics, which allows for the emission–intensity–multiplexing or emission–wavelength–multiplexing. The storage and readout strategy not only shows a great promise in the application of multidimensional rewritable optical data storage, but also opens new opportunities for advanced display technology and information security system. [ABSTRACT FROM AUTHOR]

• Micro-structures are fabricated in Pr:YLF crystals by femtosecond laser irradiation. • Dual-modulation of micro-photoluminescence is found within broad parameter windows. • Optical data are encrypted in the crystal with intensity and wavelength multiplexing. • Erasure energy threshold is demonstrated with secondary femtosecond laser irradiation. • Spatially-selective rewriting and erasure of encrypted information are realized. In transparent dielectric materials, the property modulation induced by femtosecond laser irradiation (FLI) holds great promise for optical storage due to the advantages of high resolution, material flexibility and 3D recording capability. However, the benefits are often mitigated by its incapability of information multiplexing or stringent requirements on fabrication conditions. Here, based on the dual-modulation of micro-photoluminescence (μ-PL) in Pr:YLF crystals by applying FLI, a novel strategy for optical data storage (ODS) is proposed and experimentally demonstrated. Multiple laser parameters within broad ranges can be used to fine-tune the μ-PL emission bands of Pr3+ ions to create storage voxels, which makes the information recording more feasible and flexible from a perspective of practical application. Remarkably, the dual modulation of spectral features at around 638 and 641 nm, in combination with the innovative design of voxels, make it possible to realize both emission-intensity-multiplexing and emission-wavelength-multiplexing, meeting the requirements for large memory capacity and high encryption of new generation ODS. Furthermore, the spatially selective control of μ-PL signals through secondary FLI allows for rewriting and erasure of the encoded information. This work opens new opportunities for rare-earth-doped materials in the applications of multidimensional rewritable/erasable high-density optical data storage and optical information encryption. [ABSTRACT FROM AUTHOR]