Optical Data Storage Applications Research Articles

Centennial Isomers: A Unique Fluorinated Azobenzene Macrocyclus with Dual Stability Over 120 Years

AbstractA 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.

Mixed-valence system with near-infrared electrochromism of Fe(II)-based metal-organic coordination polymers

Near-infrared electrochromic materials have garnered great attention due to their potential applications in optical data storage and military camouflage. Herein, a networked metal-organic coordination polymer bearing multi-redox centra (Fe-MCP) was successfully prepared by coordination interaction of Fe ions with D-A-D-structure ligands through the liquid-liquid interface self-assembly strategy. The resultant uniform film exhibits improved NIR electrochromic attributed to the construction of mixed-valence system. Furthermore, a sandwich-structured electrochromic device was fabricated by combining Fe-MCP electrochromic layer, a gel composed of LiClO4, PMMA, and PC as the electrolyte layer, and anodically coloring PB as an ion storage layer. The resultant device illustrated an optical contrast of 31.4 % at 800 nm and 34.2 % at 1000 nm, a response speed of 4.0 s/8.3 s at 800 nm and 7.6 s/2.7 s at 1000 nm, and good cycling durability. The design principles proposed in this study provide a new insight for the preparation of high-performance NIR electrochromic materials.

Advances in Reversible Luminescence Modification and Applications of Inorganic Phosphors Based on Chromism Reaction

AbstractThe reversible luminescence modification of inorganic phosphors has emerged as a promising field, enabling innovative applications such as optical memory, multiple anti‐counterfeiting, and photoswitches. Traditional luminescence modulation techniques, such as core–shell structure design and energy transfer‐related luminescent ions regulation, face challenges in achieving reversible luminescence modification. Chromism induces reversible color changes in materials when stimulated by external fields such as electricity, heat, and light. Combining chromism with luminescence enables the creation of chromism‐driven reversible luminescence manipulation in a single material. This review summarizes recent advances in reversible luminescence modification of inorganic phosphors based on chromism reaction and highlights their potential applications in optical data storage, fingerprint acquisition, and anti‐counterfeiting areas. The potential prospective research directions are also discussed and the challenges and opportunities of chromism‐based reversible luminescent materials are presented for further extended applications.

Persistent Charging of CsPbBr3 Perovskite Nanocrystals Confined in Glass Matrix.

Manipulation of persistent charges in semiconductor nanostructure is the key point to obtain quantum bits towards the application of quantum memory and information devices. However, realizing persistent charge storage in semiconductor nano-systems is still very challenge due to the disturbance from crystal defects and environment conditions. Herein, the two-photon persistent charging induced long-lasting afterglow and charged exciton formation are observed in CsPbBr3 perovskite nanocrystals (NCs) confined in glass host with effective lifetime surpassing one second, where the glass inclosure provides effective protection. A method combining the femtosecond and second time-resolved transient absorption spectroscopy is explored to determine the persistent charging possibility of perovskite NCs unambiguously. Meanwhile, with temperature-dependent spectroscopy, the underlying mechanism of this persistent charging is elucidated. A two-channel carrier transfer model is proposed involving athermal quantum tunneling and slower thermal-assisted channel. On this basis, two different information storage devices are demonstrated with the memory time exceeding two hours under low-temperature condition. These results provide a new strategy to realize persistent charging in perovskite NCs and deepen the understanding of the underlying carrier kinetics, which may pave an alternative way towards novel information memory and optical data storage applications.

Transparent regenerated cellulose film containing azobenzene group with reversible stimulus discoloration property

The cellulose film, exhibiting color alterations in response to external stimuli, presents itself as a promising functional material. In this study, a universal dissolution-regeneration technique was employed to manufacture a transparent, regenerated cellulose film, characterized by its reversible multi-stimulus discoloration property. This functional cellulose film, endowed with both photochromic and acid-chromic attributes, was synthesized through the introduction of a cellulose-grafted azobenzene derivative into the cellulose solution. The hue of a cellulose film irradiated with ultraviolet light could be inverted upon exposure to visible light or heat. Furthermore, when subject to heating, irradiation, or immersion in an acidic medium, this functional film demonstrated pronounced transparency. The acid-chromic behavior of the film was readily discernible when exposed to highly concentrated acidic aqueous solutions. Both the photochromic and acid-chromic phenomena were discernable to the unaided eye. After ten cycles, no fading of the reversible discoloration properties of the material occurred. This transparent regenerated cellulose film stands as a viable candidate for applications in optical data storage, intelligent switches, and sensors, owing to its capacity for reversible stimulus-triggered discoloration.

Direct photoluminescence manipulation in Er-doped AgNbO3 lead-free antiferroelectrics via reversible electric-field-induced symmetry modulations

The electric field-modulated photoluminescent (E-PL) effect has received much attention because of its potential applications in optical data storage and communication. Based on the E-induced antiferroelectric-ferroelectric (AFE-FE) phase transition, a large and reversible modulation of the PL intensity was previously realized in lanthanum-doped Pb(Zr0.9Ti0.1)O3 (PLZT) ceramics. However, such systems contain abundant leads and are thus toxic to humans and the environment. In this work, Er-doped AgNbO3 (ANO) lead-free ceramics were prepared, and their E-PL effect was investigated. From the perspective of the crystallographic symmetry, the reversibly E-induced orthorhombic Pbcm to orthorhombic Pmc21 transition results in a negative PL intensity change of 25%, which is different from the positive 30% PL modulation in the PLZT system triggered by the AFE-FE orthorhombic-rhombohedral phase transition. This symmetry-dependent negative PL modulation in ANO ceramics enriches the understanding of the E-PL effect in AFEs and provides an environmentally friendly alternative for multifunctional optoelectronics.

Directional terahertz holography with thermally active Janus metasurface

Dynamic manipulation of electromagnetic (EM) waves with multiple degrees of freedom plays an essential role in enhancing information processing. Currently, an enormous challenge is to realize directional terahertz (THz) holography. Recently, it was demonstrated that Janus metasurfaces could produce distinct responses to EM waves from two opposite incident directions, making multiplexed dynamic manipulation of THz waves possible. Herein, we show that thermally activated THz Janus metasurfaces integrating with phase change materials on the meta-atoms can produce asymmetric transmission with the designed phase delays. Such reconfigurable Janus metasurfaces can achieve asymmetric focusing of THz wave and directional THz holography with free-space image projections, and particularly the information can be manipulated via temperature and incident THz wave direction. This work not only offers a common strategy for realizing the reconfigurability of Janus metasurfaces, but also shows possible applications in THz optical information encryption, data storage, and smart windows.

Trap‐Dependent Optical/Thermal Stimulated Luminescence of Gallate Phosphors Charged by UV–visible–NIR light for Multiplexed Data Storage

AbstractUV‐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.

Photoinduced Fluorescence Switching in Molecular Aggregates by Topological [2+2] Cycloaddition

AbstractThe optical modulation of fluorescence characteristics in molecular aggregates, which mainly involves diverse molecular stacking and the consequent intermolecular interactions, remains a significant challenge for potential applications in optical anticounterfeiting, data storage, and imaging. Here we successfully realize in situ fluorescence switching in molecular aggregates of thianaphthene‐dioxide derivatives by topological [2+2] photocycloaddition, which represents a promising way to regulate the molecular stacking and alter photophysical processes. Notably, 2‐(3,5‐bis‐trifluoromethylphenyl)benzo[b]thiophene‐dioxide (BTO‐TF) in both crystal and powder forms exhibits a unique switching from an initial nonfluorescent state to a highly fluorescent state (ΦPL=0.46) upon UV irradiation, because of the destruction of the [2+2] cycloaddition process by volume expansion of the photodimer. Furthermore, we demonstrate such a [2+2] photocycloaddition can occur when 2‐(4‐carboxypheny)benzo[b]thiophene‐dioxide (BTO‐OH) is doped within selective polymer matrixes, and can be utilized for the visualization of macrophase separation in polymer blends.

Photoinduced Fluorescence Switching in Molecular Aggregates by Topological [2+2] Cycloaddition.

The optical modulation of fluorescence characteristics in molecular aggregates, which mainly involves diverse molecular stacking and the consequent intermolecular interactions, remains a significant challenge for potential applications in optical anticounterfeiting, data storage, and imaging. Here we successfully realize in situ fluorescence switching in molecular aggregates of thianaphthene-dioxide derivatives by topological [2+2] photocycloaddition, which represents a promising way to regulate the molecular stacking and alter photophysical processes. Notably, 2-(3,5-bis-trifluoromethylphenyl)benzo[b]thiophene-dioxide (BTO-TF) in both crystal and powder forms exhibits a unique switching from an initial nonfluorescent state to a highly fluorescent state (ΦPL =0.46) upon UV irradiation, because of the destruction of the [2+2] cycloaddition process by volume expansion of the photodimer. Furthermore, we demonstrate such a [2+2] photocycloaddition can occur when 2-(4-carboxypheny)benzo[b]thiophene-dioxide (BTO-OH) is doped within selective polymer matrixes, and can be utilized for the visualization of macrophase separation in polymer blends.

Modeling of inhomogeneous heating behavior in ultrafast laser interaction with dielectric–dielectric nanocomposite with band gap contrast

Inspired by the optical data storage and photothermal therapy applications of metal–dielectric nanocomposite materials relying on the difference in laser absorption mechanism between metal and dielectric, the ultrashort single pulse laser irradiation of zirconia–alumina nanocomposite, a dielectric–dielectric nanocomposite with band gap contrast, was investigated. A femtosecond (fs) laser of 250 fs pulse duration and 10 W maximum average power was used for the experiment. A seemingly unusual phase melting phenomenon - whereby the higher melting point zirconia phase (2715 °C) was melted, while the lower melting point alumina phase (2072 °C) remained intact - was observed, thereby suggesting a huge temperature heterogeneity in the composite under ultrashort single pulse laser irradiation. Theoretical modeling indicates that the material band gap plays a significant role in laser energy absorption under an intense laser field. A sharp increase in the total absorbed laser energy and concomitant temperature increase around the laser ablation threshold was revealed. Under appropriate laser fluence, the smaller band gap zirconia phase (5.8 eV) can absorb much more laser energy than the alumina phase (8.8 eV), resulting in a remarkable temperature difference between these two phases. This research demonstrates the capability of generating huge phase specific temperature differences in composite nanostructures composed of phases with band gap contrast by using ultrashort pulsed laser irradiation.

Developing "smart windows" for optical storage and temperature sensing based on KNN transparent ceramics

Smart windows have attracted considerable attention due to their wide applications in optical data storage, switchable sunroof and temperature sensing. The development strategy for smart windows is focused on performance design, enhancement and integration. However, developing integrated multi-functional smart windows in a single material remains a challenge. In this work, we have successfully prepared (K0.5Na0.5)0.95Ba0.04Er0.01NbO3 (4Ba-1Er-KNN) transparent ceramics for potential applications of temperature detection and optical information storage in smart windows. With alternating ultraviolet (UV) illumination and 300 °C thermal stimulation, the prepared 4Ba-1Er-KNN ceramics can not only achieve non-destructive luminescence readout, but also exhibits an ultra-high photochromic (PC) contrast with rapid response time of 1 s. Furthermore, based on the up-conversion (UC) photoluminescence (PL) intensity ratio of Er3+: 2H11/2/4S3/2 thermally coupled levels, excellent low-temperature sensing performance with the maximum relative sensitivity of 0.023 K−1 at 213 K is obtained. The integration between UC PL, PC response and temperature sensing performance makes it possible to develop multi-functional smart windows.

Phase Stability and Dual-Mode Photoluminescence Modulation in Er-Doped Lead Zirconate Titanate Antiferroelectrics.

The electric-field-modulation (E-modulation) of photoluminescence (PL) properties in bulk ceramics has attracted tremendous interest due to its potential application in optical data storage and communication devices. One promising approach of reversibly and largely modulating the PL intensity has been proposed in rare-earth Er3+-doped Pb0.96La0.04Zr0.9Ti0.1O3 (PLZT) antiferroelectrics (AFEs) based on the unique E-dependent antiferroelectric-ferroelectric (AFE-FE) phase transition. However, the AFE phase stability of PLZT doped with various Er contents and their E-modulated PL properties have not been systematically investigated. In this paper, the intrinsic AFE phase of PLZT-Er is found to be stabilized in the high-temperature and high-E regions with increasing Er3+ content. The enhanced AFE nature caused by increasing Er doping leads to a larger E-dependent PL tunability (∼35%). Moreover, the ceramics exhibit the characteristics of both upconversion and downconversion PL (UCPL and DCPL) effects. Based on the excellent E-dependent dual-mode PL tunability, an optoelectronic device named the optical latch is demonstrated, where an electric signal can be used to trigger a notable intensity change in both the UCPL and DCPL modes. This reversible E-dependent dual-mode capability in PLZT-Er sheds light on a feasible approach to optoelectronic applications.

Generating Ultralong-Superoscillation Nondiffracting Beams with Full Control of the Intensity Profile

Nondiffracting light beams receive substantial attention in various areas due to their properties of diffractionless propagation and achievable subwavelength beam size. Extending the propagation distance and compressing the beam size of nondiffracting beams are crucial to their practical applications. However, it remains challenging to achieve nondiffracting light beams with a subwavelength subdiffracting transverse size and a long propagation distance with controllable intensity profiles in both transverse and longitudinal directions. Here, we propose an optimization method to generate an ultralong-superoscillation nondiffracting light beam with full control of the beam intensity profile. A 45\ensuremath{\lambda}-long-superoscillation nondiffracting light beam, the transverse sizes of which are within the range of 0.37\ensuremath{\lambda}--0.4\ensuremath{\lambda} along the propagation axis, is experimentally demonstrated by a metalens based on continuous phase modulation using geometrical phase metasurfaces. Our method provides an attractive way to controllably generate ultralong-superoscillation nondiffracting beams on a subwavelength scale and might find fascinating applications in optical manipulation, materials processing, data storage, microscopy, and spectroscopy.

Two-photon absorption of FAPbBr3 perovskite nanocrystals

Perovskite nanocrystals (NCs) with high two-photon absorption (TPA) cross-section are of great interest due to their potential applications in three-dimensional optical data storage and multiphoton fluorescence microscopy. Among various perovskite materials, FAPbBr3 NCs show a better development prospect due to their excellent stability. However, there are few reports on their nonlinear optical properties. In this work, the nonlinear optical behavior of FAPbBr3 NCs is studied. The methods of multiphoton absorption photoluminescence saturation and open aperture Z-scan technique were applied to determine the TPA cross-section of FAPbBr3 NCs, which was around 2.76 × 10−45 cm4⋅s⋅photon−1 at 800 nm. In addition, temperature-dependent photoluminescence induced by TPA was investigated, and the small longitudinal optical phonon energy and electron–phonon coupling strength was obtained, which confirm the weak Pb–Br interaction. Meanwhile, it is found that the exciton binding energy in FAPbBr3 NCs was 69.668 meV, which may be ascribed to the strong hydrogen bond interaction. It is expected that our findings will promote the application of FAPbBr3 NCs in optoelectronic devices.

Multicolor upconversion reversible modulations in YNbO4:Er3+/Tm3+/Yb3+ photochromic materials

Photochromic materials with multicolor upconversion reversible modulations are attractive in optical switching devices. Herein, the fabricated YNbO4:Er3+/Tm3+/Yb3+ materials exhibit excellent photochromism and multicolor upconversion properties from green, red to near infrared (NIR) emissions with increasing Yb concentrations. Reversible multiband upconversion modulations are achieved by alternating light (365 and 405 nm) or thermal stimuli. After 365 nm irradiation, the luminescence color changes from yellow to red, the luminescent photoswitching contrast reaches up to 86.21% (green), 82.12% (red) and 77.38% (NIR) in the Y0.83Er0.01Tm0.01NbO4:0.15 Yb sample. Besides, the upconversion emission intensity before and after photochromic reaction shows remarkable change in a wide temperature range of 298–718 K. These results indicate that the Er3+/Tm3+/Yb3+ tri-doped YNbO4 materials can be a good candidate in optical switching and data storage applications.

Linear charging-discharging of an ultralong UVA persistent phosphor for advanced optical data storage and wide-wavelength-range detector

Ultraviolet persistent luminescence (UV PersL) phosphor is currently gaining considerable attention due to its promising potential for widespread advanced applications. However, the linear manipulation of electron charging-discharging and the prolongation of persistent time remains a huge challenge. Here, we report a novel Bi3+ doped Mg2GeO4 UVA PersL phosphor via a nonequivalent substitution strategy. The UVA PersL performance of Mg2GeO4:Bi3+ is significantly improved by introducing Li+ ions, yielding a superior UVA PersL property with afterglow lasting time beyond 100 h. The trap distribution management and the captured electron motion dynamics are revealed by the thermoluminescence technique under various external stimuli. Moreover, UVA PersL can be repeatedly rejuvenated by NIR and blue LED stimulation owing to the optically stimulated electrons from different depth traps to shallow traps. Due to the invisibility of UVA light, barcode information stored on the phosphor film can be read by NIR light and then erased by blue light, exhibiting the potential application in optical data storage with good concealment and security. Most remarkable is the electron charging-discharging linear functions of the irradiated power of UV, and blue and NIR light which was never reported, providing a feasible approach for optical power detection in a wide-wavelength-range. This work not only offers a guideline to develop novel high-performance UV PersL materials but also provides a route to effectively manipulate the electrons in the traps toward applications in advanced optical information storage and wide-wavelength-range light detection.

Organic Near‐Infrared Luminescent Materials Based on Excited State Intramolecular Proton Transfer Process†

Comprehensive SummaryOrganic near‐infrared (NIR) luminescent materials have captured intense research interest owing to their potential applications in optical communication, data storage, bioimaging, sensing and night vision. Excited state intramolecular proton transfer (ESIPT) process with absorption in normal form while emission in tautomer form can lead to a distinct redshift emission, based on which, a lot of organic NIR luminescent materials were designed. Because of attractive features such as ultrahigh sensitivity to the surroundings, large Stokes shift, and inherent four level system, ESIPT based NIR luminescent materials are supposed to be ideal fluorescent probes and gain materials. In this review, first, organic near‐infrared luminescent materials based on ESIPT process are summarized according to the core structures. Second, recent advances of ESIPT‐based organic near‐infrared fluorescent probes and organic NIR lasers are reviewed. Finally, the current challenges and prospects of ESIPT‐based organic NIR luminescent materials are introduced.

Better colloidal lithography: Tilt-rotate evaporation overcomes the limits of plasma etching

Colloidal lithography (CL) is a promising method for large-area fabrication of nanohole and nanodot arrays with applications in optical biosensing, separations, and magnetic data storage. However, reducing the diameter of the polystyrene sphere mask by plasma etching unavoidably increases their coefficient of variation (CV) and deforms their shape, thereby limiting the pitch-to-hole-diameter ratio of the resulting nanohole array to less than 3:1 and the minimum hole size to 200 nm with a 10% or better CV. We show that tilt-rotate evaporation colloidal lithography (TRE-CL) breaks the trade-off between hole diameter and polydispersity by leveraging glancing angle evaporation, not plasma etching, to adjust the hole size. TRE-CL allows pitch-to-hole-diameter ratios as high as 7:1 and nanohole diameters down to 60 nm while maintaining a nearly constant CV below 10% and hole circularity above 91%. We transfer these hole arrays into ultrathin Si3N4 films to form nearly-monodisperse microsieves for separation applications. Furthermore, we extend TRE-CL to fabricate adhesion-layer-free plasmonic Au nanodot arrays down to 70 nm in diameter with 10% CV.

Ultraviolet C random lasing at 230–280 nm from Pr3+ doped bulk crystal resonators by two-photon absorption

Ultraviolet solid-state light sources, especially in the short-wave ultraviolet band, are attracting great attention for potential applications in high-density optical data storage, biomedical research, and water and air purification and sterilization. As one of the means to generate solid-state short-wavelength lasers, upconversion technology, which can transform a low-energy photon to a high-energy photon, has a simple structure and does not require strict phase-matching conditions. However, because of the high non-radiative decay rate during multiphoton absorption process, the short-wave upconversion ultraviolet lasing is still difficult to achieve. Here, under 450 nm blue laser excitation, we have successfully obtained ultraviolet C random lasing from a Pr3+ doped YPO4 single crystal via two-photon absorption. Presently, ultraviolet C random lasing with the wavelength range of 230–280 nm is the shortest wavelength for upconversion lasing emission.