Optical Data Storage Applications Research Articles

New insights into phosphorescence properties of LuAGG: Long afterglow phosphor-in-glass for optical data storage

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. Lu3Al2Ga3O12: Ce3+, Cr3+ (LuAGG: Ce3+, Cr3+) based on TBZNA glass could emit bright green light signal located at 350 and 420 nm ascribed to the 5d1/5d2-4f 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.

Fluorochromic polymeric elastomer film containing copper nanoclusters in response to multistimuli

Smart chromic elastomers exhibiting multistimuli responsiveness are of interest with regard to the development of sensors, optical data storage, and smart wearable devices. We report a new design of Cu nanoclusters (Cu NCs) containing polymeric elastomer film, showing reversible fluorescence ON/OFF when subjected to organic solvents (e.g. ethanol, methanol and tetrahydrofuran), and heating/cooling cycles at temperatures lower than 80 °C. Different from the solvato-responsiveness of Cu NCs in solution state, organic solvents increase nonradiative decay and quench fluorescence emission in the solid polymer matrix. It is deduced that lower temperatures (<80 °C) increase reversible nonradiative decay, while higher temperatures (>80 °C) trigger an irreversible change of the aggregation state of Cu NCs in the elastomer film. A strong oxidizer (e.g. H2O2) irreversibly quenches the fluorescence emission and changes its color (under sunlight) from light green to blue, by oxidizing Cu NCs to Cu2+ ions. This Cu NC-containing elastomer film illustrates a new pathway to the fabrication of multi-responsive smart optical materials, particularly for potential applications in optical data storage (e.g. thermo-printing), and multistimuli-responsive elastomeric sensors integrated into wearable devices.

Solid-state photochromic molecular switches based on axially chiral and helical spiropyrans

Solid-state photochromic switches with reversible luminescence modulation property have wide applications in optical data storage, anticounterfeiting, sensing, and bioimaging, however, it is a significant challenge to design and prepare such materials. In the present work, a novel class of chiral and helical binaphthyl-substituted spiropyrans has been synthesized and characterized. The introduction of binaphthyl can not only promote the solid-state luminescence but also achieve the interesting chiroptical switching properties for the potential applications in chiral recognition and circularly polarized luminescence. The single-crystal structures and density functional theory calculations reveal that the presence of strong electron-withdrawing nitro groups can promote photoswitch efficiency by stabilizing the electron-rich conjugated merocyanine with the lower electron cloud density and LUMO/HOMO levels. For charge transfer in excited states, π → π* transition would enhance emission, but n → π* transition and intramolecular charge transfer show the opposite effect. Therefore, these photochromic switches provide a novel paradigm in the design of multiple-responsive, chiral, and luminescent materials.

Polarization domain wall solitons in a quasi-isotropic fibre laser using quantum dot tungsten disulfide

A passively fast polarization switching erbium-doped fibre laser using quantum dot tungsten disulfide (QDWS2) as a saturable absorber (SA) has been proposed. It could generate polarization domain walls (PDWs). The PDWs‘ spectrum can be divided into two separated spectra, which are orthogonally polarized. In detail, the horizontal polarization component wavelength is centred at 1561.1 nm with a repetition rate of 19.347 MHz, a pulse duration of 30 ns, and a signal-to-noise ratio of 73.2 dB at the maximum pump power. The vertical polarization component wavelength is centred at 1561.5 nm, with a pulse duration of 20.4 ns. To the best of our knowledge, this is the first report of a polarization domain wall generated by a QDWS2-SA. These results provide a platform to investigate anticorrelated polarization dynamics in quasi-isotropic fibre lasers. Moreover, their robustness and attractive properties could find potential applications in optical communications, data storage, and fibre laser devices.

Fluorochromic polymer films containing ultrasmall silver nanoclusters

Fluorochromic materials that change their emission properties in response to their environment are of interest for the development of sensors, optical data storage and light-emitting materials. A thermally fluorochromic elastic polymer film that exhibits remarkable fluorochromism (from red to yellow) and enhancement of fluorescence intensity after thermal treatment (>120 °C) is designed by the incorporation of silver nanoclusters. The thermal treatment also leads to a significant increase of quantum yield and fluorescence lifetime. It is found that the thermo-induced etching on larger silver nanoclusters generates smaller silver nanoclusters. This simple and efficient size-tuning process in solid state is responsible for the thermo-fluorochromism and enhancement of fluorescence emission from silver nanoclusters. Such a thermo-fluorochromic polymer material is finally demonstrated to be useful for thermo-printing. This material illustrates a new way to make smart optical materials, particularly for potential applications in optical data storage and soft OLED display.

Cyanine dyes

Abstract Cyanine dyes are characterized by an odd number 2n + 3 of π-centers and 2n + 4 π-electrons (where n is the number of vinyl groups –CH = CH–). This special feature has a marked impact on their electronic structure and thus their equilibrium structure in the electronic ground state as well their color and electronic spectrum, respectively. Their first technical application was the use as spectral sensitizers in silver halide photography. Today they have numerous of applications in digital optical data storage, Computer-to-Plate lithographic printing plates, bio-analysis and medical diagnostics.

Synthesis and characterization of ZnO NPs-doped PMMA-BDK-MR polymer-coated thin films with UV curing for optical data storage applications

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.

Near-infrared emitting microspheres of LaAlO3:Mn4+: Defects engineering via Ge4+ doping for greatly enhanced luminescence and improved afterglow

Perovskite-type microspheres of LaAlO3:xMn4+,yGe4+ have been fabricated through thermal decomposition of the amorphous precursors autoclaved from the nitrates and ethylene glycol in the prescence of citric acid. LaAlO3:xMn4+ spheres emit broad and bright near infrared (NIR) emission ranging from 680 nm to 750 nm with the maximum at around 730 nm. The quenching concentration for Mn4+ in LaAlO3 is found at x = 0.1%. In the absence of light source, the spheres emit intense NIR afterglow for 10 min at room temperature, mainly due to the formation of [MnAl] defects. Doping Ge4+ does not significantly change the morphology, crystal structure, band gap, and thermal stability of LaAlO3:Mn4+ sample, but it induces stronger asymmetry of MnO6 and more isolated Mn4+ ions, which thus contributes to greatly enhanced NIR emission intensity by 260%. Ge4+ ions occupying Al site leads to the formation of positive [GeAl] defects, which are closely related to the trap concentration rather than the trap depth. Incorporation of Ge4+ gives rise to the improved persistent luminescence, and the most intense afterglow is found at y = 0.6%. The spheres exhibit repeatable afterglow by a proper heat processing in the absence of light source, indicating their potential application in optical data storage.

Zn2+ responsive fluorescence enhancement for optical data storage.

In this paper, we put forward a new application in optical data storage (ODS) of tetraphenylethene (TPE)-doped photopolymer, which has an aggregation-induced emission attribute. The photopolymer host reacted with the excitation light at the focal point of a high numerical-aperture lens to enhance the fluorescence intensity mainly because of the function of the ${{\rm Zn}^{2 + }}$Zn2+ ion. We recorded data inside the photopolymer matrix by using this property and had distinct fluorescence intensity contrast between the photochemical regions and other regions. This attribute paves a new way for superresolution ODS and opens the way to exploring the possibility of utilizing TPE-doped photopolymers as chemical sensors in the future.

A 4-N,N-dimethylaminoaniline salicylaldehyde Schiff-base solution-solid dual emissive fluorophore: An aggregation-induced turquoise emission characteristics in liquid as a fluorescent probe for Zn2+ response; a strong near-infrared emission in solid state and application for optical data storage.

A new Schiff-base 1 based on 4-N,N-dimethylaminoaniline salicylaldehyde is developed. It possesses unique solution-solid dual emission behaviour with emission color: an aggregation-induced bright turquoise emission in liquid and strong near-infrared emission in the solid state. Interestingly, on the one hand, compound 1 is promising a ratiometric fluorescent probe for Zn2+ ions detection in the aqueous solution with high sensitivity, selectivity, and relatively low detection limit. On the other hand, based on its inner stimuli-responsive nature, outstanding thermostability and photostability, 1 should be a very promising candidate for the write-once read-many optical data storage medium.

Dual-polarization star-gap nano-antenna

Nano-antennas are used in optical data storage, near-field imaging, photovoltaics, sensing, and spectroscopy applications. In many cases, the antennas work with linear polarization, but some applications require circularly polarized (CP) light such as field-enhanced circular dichroism spectroscopy. Circular dichroism spectroscopy is a technique used to study organic molecules and is widely used in biology and medicine. In this article, we analyze a star-gap nano-antenna array. The antenna combines concentric circular gratings and a symmetric gap to provide a maximum electric field enhancement factor of around 48 at 780 nm with the average electric field enhancement factor of about 34.75. Due to its geometry, the antenna can work for both linearly polarized and CP light, having similar electric field enhancement factors. Due to its symmetry and capacity to work with different polarizations, the antenna can find applications in sensing and spectroscopy. As an example of application, we have characterized the antenna for surface enhanced Raman scattering (SERS) and obtained a SERS factor of 4.18×106 for the 880cm−1 Raman line of ethanol.

Blue-/NIR Light-Excited Fluorescence Switch Based on a Carbazole-Dithienylethene-BF2bdk Triad.

The development of novel solid-state fluorescence switches, particularly triggered by visible light, is of increasing interest for the potential application in optical data storage and super-resolution fluorescence microscopies. In this study, two carbazole-dithienylethene-BF2bdk triads CDB1 and CDB2, suspending carbazole and BF2bdk moieties on both sides of dithienylethene unit, have been developed. They exhibit blue-/NIR light-controlled photochromism with solvent-dependent characteristics. Moreover, CDB1 (o) reveals blue-/NIR light-induced reversible fluorescent switching behaviors in toluene, chloroform, poly(methyl methacrylate) (PMMA) film, and powder state, while its analogue CDB2 (o) in the powder state exhibits no fluorescence due to a strong intermolecular π-π stacking interaction, and the fluorescent switching performance is observed only in toluene and PMMA film. The density functional theory calculations further validate the differences in their optical properties in the solution and powder states.

Circularly Polarized Luminescence in Nanoassemblies: Generation, Amplification, and Application.

Currently, the development of circularly polarized luminescent (CPL) materials has drawn extensive attention due to the numerous potential applications in optical data storage, displays, backlights in 3D displays, and so on. While the fabrication of CPL-active materials generally requires chiral luminescent molecules, the introduction of the "self-assembly" concept offers a new perspective in obtaining the CPL-active materials. Following this approach, various self-assembled materials, including organic-, inorganic-, and hybrid systems can be endowed with CPL properties. Benefiting from the advantages of self-assembly, not only chiral molecules, but also achiral species, as well as inorganic nanoparticles have potential to be self-assembled into chiral nanoassemblies showing CPL activity. In addition, the dissymmetry factor, an important parameter of CPL materials, can be enhanced through various pathways of self-assembly. Here, the present status and progress of self-assembled nanomaterials with CPL activity are reviewed. An overview of the key factors in regulating chiral emission materials at the supramolecular level will largely boost their application in multidisciplinary fields.

Liquid crystal and photo-induced properties of polymers carrying pyridylazobenzene groups and iodopentafluorobenzene rings self-assembled through halogen bond

In this work, we report on the synthesis, liquid crystal behavior and photo-induced optical properties of a polymer and a copolymer, both carrying lateral pyridylazobenzene groups and iodopentafluorobenzene (IPFB) rings self-assembled through halogen bond. The formation of the halogen-bonded complexes was confirmed by Fourier transform infrared (FTIR) spectroscopy; the mesomorphic behavior was determined by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD); and the optical properties were photo-induced with a 405 nm laser beam. The pyridylazobenzene-functionalized polymer showed a smectic-type order (smectic A and crystE phases) whereas the copolymer and the halogen-bonded complexes with IPFB rings formed aggregates whose molecular order in the z-coordinates is suppressed (no layers). The photo-isomerization (in solution) of the polymer and copolymer led to a trans-to-cis isomer conversion (%cis) of 82, and 95, respectively. In film, the %cis values resulted much inferior but still high enough to induce optical properties, as for instance, in films of the copolymer (%cis = 60) and its halogen-bonded complex (%cis = 46) that responded quite well in periodical light-induced writing/erasure experiments. Only the halogen-bonded copolymer complex allowed us to register regular surface relief gratings (SRGs) suggesting that it would be a good candidate for optical data storage applications.

Rotating vortex-like soliton in a whispering gallery mode microresonator

The vortex soliton has gained interest in recent years due to its intriguing potential applications in optical data storage, data processing and other areas. In this work an extensive analysis of characteristic features of the vortex-like soliton in a whispering gallery mode microresonator is carried out within the framework of the (2 + 1)-dimensional Lugiato-Lefever equation. It is found that the external pump field will cause the vortex-like solitons to rotate, and these vortex-like solitons can remain stable after increasing the white noise by 5%. Furthermore, the effects of topological charge, diffraction coefficient and self-focusing/self-defocusing nonlinearity on the properties of the vortex-like soliton in the whispering gallery mode microresonator are investigated. The results show that with the increase in topological charge, the vortex-like solitons will expand and the number of layers will increase. Finally, the breathing behavior is revealed when interaction between two vortex-like solitons occurs. Theoretical studies on vortex-like solitons dynamics indicates that WGM microresonators can serve as a powerful platform for exploring the nonlinear dynamics in optical nonlinear cavities. Our results are beneficial to the understanding of the fundamental dynamics of WGM microresonator solitons and extending their practical applications.

Enhanced single-mode lasers of all-inorganic perovskite nanocube by localized surface plasmonic effect from Au nanoparticles

Miniaturized laser sources recently attracted considerable interests as their potential applications in optical communication, data storage, and imaging. However, high cavity losses induced by size reduction from the gain medium would lead high lasing threshold. In this work, the enhanced optical properties of CsPbBr3 perovskite nanocubes by using localized surface plasmonic effect of Au nanoparticles (NPs) were investigated. The integration of Au NPs in the poly (3, 4-ethylenedioxy-thiophene): poly (styrenesulfonate) PEDOT: PSS layer induces obviously enhancement both in the absorption and photoluminescence (PL) of CsPbBr3 perovskite nanocubes. Importantly, the lasing threshold of CsPbBr3 perovskite nanocubes is significantly reduced by ~ 33%. This study suggests that the lead halide perovskites hybridized with plasmonic nanomaterials would be promising candidates for laser devices and other optoelectronic devices with high efficiency.

Plasmonic polymer nanocomposites

The optical properties of metal nanoparticles, particularly their localized surface plasmon effects, are well established. These plasmonic nanoparticles can respond to their surroundings or even influence the optical processes (for example, absorption, fluorescence and Raman scattering) of molecules located at their surface. As a result, plasmonic nanoparticles have been developed for multiple purposes, ranging from the detection of chemicals and biological molecules to light-harvesting enhancement in solar cells. By dispersing the nanoparticles in polymers and creating a hybrid material, the robustness, responsiveness and flexibility of the system are enhanced while preserving the intrinsic properties of the nanoparticles. In this Review, we discuss the fabrication and applications of plasmonic polymer nanocomposites, focusing on applications in optical data storage, sensing and imaging and photothermal gels for in vivo therapy. Within the nanocomposites, the nanoporosity of the matrix, the overall mechanical stability and the dispersion of the nanoparticles are important parameters for achieving the best performance. In the future, translation of these materials into commercial products rests on the ability to scale up the production of plasmonic polymer nanocomposites with tailored optical features.

Reversible upconversion switching for Ho/Yb codoped (K,Na)NbO3 ceramics with excellent luminescence readout capability

AbstractLuminescent readout capability for photochromic materials plays a critical role in 3D optical data storage applications, especially for inorganic photochromic materials in the solid‐state form. In our previous studies, we found that the luminescent readout capability can be improved using two or multiple‐photon excited luminescent mode (upconversion), which can effectively decrease the destruction degree of the excitation energies to the stored information during the luminescent “reading” process. However, the luminescent readout performance is unsatisfactory owing to the absence of nondestructive luminescence readout capability. Herein, we report a new solid‐state photochromic material with excellent upconversion readout capability: Ho3+/Yb3+ codoped (K,Na)NbO3. Upon 407 nm light irradiation, the luminescent switching contrast (ΔRt) is up to 78%. Particularly, the materials almost have no any re‐absorption to 980 nm light, exhibiting extremely low destruction to information recording points. The luminescent readout intensity retains 96% after constant 980 nm irradiation for 4 minutes at a high pumping power of 1W, which is superior to our previously reported results (Er/Yb codoped Bi2.5Na0.5Nb2O9 materials). This work would help to further develop new inorganic photochromic materials with high performance to satisfy the requirements for optical storage devices.

An isolated deep-trap phosphor for optical data storage

Next generation optical storage based on photostimulated luminescence (PSL) materials is a significant data storage technology for the information age. For a better signal durability and resolution, it is necessary to develop PSL phosphors with deep traps in a narrow distribution. Accordingly, in this short letter, we report a unique Y2GeO5:Pr3+ PSL phosphor with a narrow trap distribution (0.3 eV) and a trap depth of 1.31 eV, which is presently the deepest value. After charging by ultraviolet (254 nm) irradiation (data writing), the PSL of Pr3+ can be stimulated by an 808 nm (1.53 eV) laser (data reading). This finding reveals that electrons stored in the deep traps are sufficiently stable under a thermal disturbance at room temperature and even under stimulation by a 980 nm (1.26 eV) laser. Additionally, the deep traps are isolated and demonstrate little interference with the shallow traps. Therefore, the deep-trap Y2GeO5:Pr3+ phosphor shows potential applications in optical data storage.

Spectral, optical, etching, second harmonic generation (SHG) and laser damage threshold studies of nonlinear optical crystals of l-Histidine bromide

Nonlinear optical (NLO) materials find broad applications in optical data storage, lasers, optical signal processing, second harmonic generation, etc. Though a large number of nonlinear optical materials are available, their applications are limited due to physical and chemical properties.Since the nonlinear optical crystals of amino acids contain a proton donor carboxyl acid (COOH) group and the proton acceptor amino (NH2) group, they are considered as the apt materials for NLO applications. In the present work, good quality crystals of l-Histidine bromide were grown by using slow evaporation technique. The FTIR spectral analysis reveals the presence of different vibrational bands of l-Histidine Bromide.The optical characteristics were assessed by UV–vis analysis, which shows that the crystals have a transmission in the visible range.The etching studies were performed on the crystals, which shows that the crystal does not undergo considerable deformation under the action of solvents. The refractive index of the l-Histidine Bromide crystal was found by Brewster's angle method as 1.516. The Second harmonic generation studies and laser damage threshold studies reveal that crystals have comparable SHG conversion efficiency and high laser damage threshold value to that of the standard KDP crystal, thus making the crystals suitable for applications.