Optical Storage Applications Research Articles

Optical bistability of graphene embedded in parity-time-symmetric photonic lattices

We investigate the optical bistability of graphene in parity-time-symmetric (PT-symmetric) photonic lattices incorporated with a defect at terahertz frequencies. The field localization of the defect mode can strengthen the nonlinearity of graphene to achieve low-threshold bistability. The nonlinearity is further enhanced, and the bistability threshold decreases, by increasing the gain-loss factor in the PT-symmetric structure. The interval of upper and lower bistability thresholds is broadened as the exceptional points split. Moreover, we show the phase transition between bistability and nonbistability by modulating the incident wavelength and chemical potential of graphene. The study may find great applications in all-optical switches and optical storage.

Effects of barium substitution on the optical and electrical properties of PLZT transparent electro-optical ceramics

Abstract Transparent electro-optic (EO) ceramics Pb0.91-xLa0.09Bax(Zr0.65Ti0.35)0.9775O3 (PLBZT x/9/65/35) with the amount of x = 0, 0.01, 0.02, 0.04 barium substitution for Pb at A-site were fabricated by hot pressing sintering process. The effects of barium substitution on the micro structure, ferroelectric, dielectric, optical and electro-optic birefringence properties were systematically studied. XRD result shows a typical ABO3 perovskite structure and no second phase observed within the detection limit, which clarifies the entry of Ba2+ ions into PLZT that caused the expansion of the crystal lattice. Due to the mixing ion effect of Pb2+, Ba2+ and La3+ at A-site, both coercive field (Ec) and remnant polarization (Pr) show reducing tendency with increasing doping. And the temperature of the dielectric maximum (Tm) was decreased almost linearly with increasing barium modifying amount. Especially, the reduction of the ferroelectric hysteresis was observed, which may reveal the Ba doping a new method to solve the problems faced now in device designing. In summary, the easily tuned Tm and slim hysteresis loop may prove PLBZT a promising candidate for optical modulator, light switch, energy storage and other relevant applications.

A Photostimulated BaSi2O5:Eu2+,Nd3+ Phosphor‐in‐Glass for Erasable‐Rewritable Optical Storage Medium

AbstractUp‐to‐date optical storage technology calls for large memory capacity, expanded storage dimension, rewritable capability, low cost, and high energy efficiency, which poses stringent requirements on the storage medium. In this study, a novel BaSi2O5:Eu2+,Nd3+ photostimulated luminescence (PSL) phosphor is developed and then made into phosphor‐in‐glass (PiG) storage medium. Upon ultraviolet light irradiation (write‐in), the generated electrons are captured by the traps, which can be further released by thermal or near‐infrared laser stimulation (read‐out). An insightful investigation is carried out to establish the relationship between trap properties and PSL performance. Demonstration application confirmed the intensity‐multiplexing optical information (including the designed bar code, quick response (QR) code, graphic patterns, and binary data) encoding/decoding. Remarkably, BaSi2O5:Eu2+,Nd3+ PSL PiG show excellent erasable‐rewritable capability thanking to the admirable anti‐ultraviolet property in glass host, as well as good optical data retention ability owing to the spatially isolated deep traps. Hopefully, the present work can push forward the research progress of PSL material and its practical application in optical storage.

Evaluating the Surface Chemistry of Black Phosphorus during Ambient Degradation.

Black phosphorus (BP) is emerging as a promising candidate for electronic, optical, and energy storage applications. However, its poor ambient stability remains a critical challenge. Evaluation of few-layer liquid-exfoliated BP during ambient exposure using X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy allows its surface chemistry to be investigated. Oxidation of liquid-exfoliated few-layer BP initially occurs through nonbridging oxide species, which convert to bridging oxide species after ambient exposure. We demonstrate the instability of these bridging oxide species, which undergo hydrolysis to form volatile phosphorus oxides and evaporate from the BP surface. FTIR spectroscopy, scanning transmission electron microscopy, and atomic force microscopy were used to confirm the formation of liquid oxides through a continuous oxidation cycle that results in the decomposition of BP. Furthermore, we show that the instability of few-layer BP originates from the formation of bridging oxide species.

Layered photochromic films stacked from spiropyran-modified montmorillonite nanosheets.

Two-dimensional (2D) nanosheets are a class of fascinating host material that demonstrates a high specific surface area for the immobilization of functional molecules. Herein, we describe a layered photochromic film using montmorillonite 2D nanosheets immobilized with spiropyran units, which demonstrates a remarkable and reversible photochromic behavior. The synthesis of the layered photochromic film includes the intercalation and exfoliation of montmorillonite powders into 2D nanosheets using a spiropyran-modified surfactant and a subsequent vacuum filtration. The photochromic units of spiropyran-modified quaternary ammonium groups are immobilized on the surface of montmorillonite 2D nanosheets through an electrostatic interaction after exchanging with the native cations in montmorillonite during the intercalation and exfoliation. The photoisomerization of the spiropyran units between closed-ring spiropyran and open-ring merocyanine upon visible/UV irradiation contributes to the photochromic behavior of the layered film. The color contrast between the coloration and decoloration states of photochromic film is optimized by increasing the amount of spiropyran-modified cationic surfactant during the intercalation and exfoliation process. Our layered films with a visual photochromic behavior may promote their applications for optical data storage, optical switching and chemical sensing.

Tunable property of non-linear optical Ag – nanoclusters

Abstract Effectively modulate and tunable optical properties of the Ag-nanocluster ligated with glutathione was synthesized to exploited the covalent nature of precursor salt, strength of the reducing agent to develop versatile methodologies to get a monodisperse with desired properties. Recent study reveals that fascinating optical properties are not only because of metal core (quantization effect), it can also be tuned by surrounding ligand environment.Authors interest to demonstrate the simple method to control the size, chemical composition and non-linear optical properties of Ag nanoclusters surrounded by non-toxic, bio-compatible ligand, glutathione. The synthesized biocompatible silvernanoclusters can be very much useful for biosensor, optical storage, water puri-fication and catalytic applications.

Preparation of Photo-responsive Film by Electrochemical Deposition Method and the Application in Optical Information Storage†

Preparation of Photo-responsive Film by Electrochemical Deposition Method and the Application in Optical Information Storage†

Cr3+-doped Mg4Ga4Ge3O16 near-infrared phosphor membrane for optical information storage and recording

A new near-infrared phosphor Mg4Ga4Ge3O16: Cr3+ with multi-photo-functionalities has been developed. Such phosphors can act as luminescent down-shifting materials converting UV and visible photons into NIR light (600–850 nm). UV irradiation induced strong NIR long persistent luminescence (LPL) can persist for more than 10 h. With the prolonged decay time, the extinguished NIR LPL can be rejuvenated by external photo stimulus including not only 980 nm light but also visible light. Such NIR photostimulated persistent luminescence (PSPL) presents separated write-in and read-out wavelength ranges. Meanwhile, photochromism (PC), that the material surface undergoes reversible change between white/pale green and ronbrown when triggered alternatively by UV and visible irradiation/heating, was also observed. Several recycle measurements demonstrate the robust fatigue resistance of PC property. Owning to the multi-photo-functionalities of Mg4Ga4Ge3O16: Cr3+, the fabrication of flexible phosphor membranes endows their application for optical information storage and repeatable optical recording. The electron motion in traps was studied by thermoluminescence (TL) and the color center formation was verified with electron spin resonance (ESR) spectra, based on which an energy level diagram was proposed for the illustration of the multifunctional mechanism. The revealing of multi-photo-functional mechanism and fabrication of flexible phosphor membranes may promote the development of a universal design principle for further study.

(Invited) the Progress and Outlook of GaN Laser Devices

GaN laser diodes are considered the next frontier for high performance GaN optoelectronics. Currently, GaN edge-emitting laser diodes are finding specific applications in optical information storage, in large-area projection, and in automobile headlights. It is widely anticipated that further advances in GaN laser diodes could enable a much broader range of applications in lighting and display. The purpose of this presentation is to provide a high-level analysis of the state of two types of GaN laser diodes; one is the edge-emitting laser (EEL) and the other is the vertical cavity surface emitting laser (VCSEL). Commercial GaN EEL has been available for more than 15 years but the performance (wall-plug efficiency) is limited to ~35%[1]. For GaN VCSELs, in spite of various laboratory demonstrations in the past 10 years, there has not been any commercial product as a result of complexity involved in the growth and fabrication. For the discussion of GaN EELs we will analyze the factors that define and limit the contemporary GaN EELs. New approaches such as using non-polar/semipolar planes [2], quantum-dot active regions [3], higher power operation [4], and our unique approach of engineering the optical cavity confinement [5] will be discussed. Concerning GaN VCSELs, the technological bottleneck has been the formation of distributed Bragg reflectors (DBRs) for a planar microcavity. We will review the pros and cons of several approaches including epitaxial DBRs (AlGaN [6] or AlInN [7]), dielectric DBRs involving layer separation and transfer [8]–[10], and later overgrowth on dielectric DBRs [11]. Special emphasis will be given to our effort in using a nanoporous medium to form an epitaxial, conductive, and highly reflective DBRs for VCSELs [12], [13]. This work is supported the National Science Foundation (NSF) under Award ECCS-1709149 and by DARPA MTO of the United States. The facilities used were supported by the Yale SEAS cleanroom, YINQE, and NSF MRSEC DMR-1119826.

Investigation of reversible photoluminescence switching driven by colorless-purple photochromism in Sr5(PO4)3F:Eu2+ for optical storage applications

We report a novel photoresponsive powder material, haloapatite Sr5(PO4)3F:Eu2+, which exhibits good photochromic properties and undergoes reversible colorless-purple color changes after alternative UV and visible irradiation/heating. The effect of Eu2+ doping concentration on the photochromic behavior is investigated, and the optimum doping concentration of Eu2+ is found to be approximately 0.5 mol%. Further recycling coloring-bleaching measurements at room and high temperature confirm the high fatigue resistance of the material and the good thermal stability of its photochromic performance. Based on these findings, the photoluminescence performance of the present material can be effectively modulated through its photochromism. A luminescence switching efficiency of up to ∼40% is obtained for x = 0.005. The present results allow discussing the critical role of the charge carrier dynamics in the photochromism. Finally, we propose a tentative model illustrating the photochromism and luminescence modulation mechanisms.

Photothermoplastic recording media and its application in the holographic method of determination of the refractive index of liquid objects.

The photothermoplastic medium based on the films of photosensitive polymeric composites with semiconductor properties is developed for application in optical information recording and storage, in holographic interferometry, as well as for medical purposes. This medium was used in the modified holographic device for determination of changes of the refractive index of homogeneous and inhomogeneous liquid objects. The technique and holographic equipment were modified by employing the specially developed and produced transparent cuvette of special shape and the phase shifting interferometry method. Experimentally demonstrated precision of the measurements is not less than 10-5.

Nonlinear optical and multi-photon absorption properties in graphene–ZnO nanocomposites

Graphene–ZnO (GZO) nanocomposites were synthesized by a modified solvothermal method, and characterized by transmission electron microscopy, x-ray diffraction, Raman spectra, and UV–vis absorption spectra. The controllable nonlinear optical (NLO) properties of as-prepared GZO nanocomposites were tested by an open-aperture Z-scan method with 1030 nm fs laser pulses; the tested results showed that there were five-photon absorption (5PA) at 46.8 GW cm−2, 3PA at 28.1 GW cm−2, 2PA at 18.7 GW cm−2, and a vital change from saturable absorption (SA) to reverse SA (RSA) with the increase of incident intensity. This was the first time that 5PA was found in GZO nanocomposites at such a low intensity, 46.8 GW cm−2. The tunable NLO property from SA to RSA and controllable multi-photon absorption provided a facile approach for their applications in optical, optoelectronic devices, and information storage.

二芳基乙烯的光学性质及其在超分辨光存储中的应用

二芳基乙烯的光学性质及其在超分辨光存储中的应用

Turn-off mode fluorescent norbornadiene-based photoswitches

Single-molecule fluorescence emission of certain positive photochromic systems such as diarylethenes have been exploited for biological imaging and optical memory storage applications. However, there is a lack of understanding if negative photochromic systems can be used for such type of applications. Hence, to explore the potential of negative photochromic molecules for possible optical memory storage applications, we have here synthesized and studied a series of four norbornadiene-quadricyclane (NBD-QC) photoswitching molecules. These molecules feature either linearly conjugated or cross-conjugated pi-electron systems. Upon photoisomerization, the UV-vis absorption spectra of the molecules revealed a strong blue shift in the QC-form, with a photoisomerization quantum yield close to 80% for the cross-conjugated systems. In contrast, a strong intrinsic emission (up to Φf = 49%) for the linearly conjugated compounds in the NBD form was observed. Upon light-induced isomerization, the emission was completely turned off in the QC-form in all the compounds studied. Further, the robustness of the system was evaluated by performing several switching cycles. Under nitrogen, the emission can be turned off and recovered with almost no loss of emission. We also show that the QC-form can be photochemically triggered to convert back to the NBD-form using a low energy UV light (340 nm), allowing an all optical conversion to both species. The demonstrated properties can make the NBD-QC system attractive for potential applications such as optical memory storage devices.

Numerically investigating the optical properties of plasmonic metallic nanoparticles for effective solar absorption and heating

Solar heating with plasmonic nanoparticles (NPs) has great potential for application in optical storage, solar thermal collectors, and thermo-photovoltaic technologies. The performance of solar thermal conversion applications depends on the NP parameters. Herein, we present a comparative analysis of the solar absorption properties of noble metallic NPs (Au, Ag, Cu, and Al), to determine suitable parameters for effective solar heating by using the finite-difference time-domain method and the finite-element method. Results show that light absorption plays a major role in the interaction of light with the small NP size, small sphericity, or small dielectric constant of the surrounding environment. Au and Cu NPs have higher solar absorption power and absorption ratio. The NP size has little effect on the peak absorption wavelength. A Au sphere smaller than 30 nm has greater solar absorption ability for the solar heating process when considering the absorption power per unit volume. The solar absorption power first increases rapidly and subsequently decreases slightly with increasing dielectric constant, and can become as high as 0.0045 nW when the dielectric constant is 1.33–2.5 in the calculation samples. The solar scattering power and solar absorption power decrease with increasing sphericity, i.e., ranging from cubic to cylindrical and spherical. Finally, simulation results of NP solar heating show that the Au cube obtains a higher maximum temperature than the Au sphere and Au cylinder, which further verifies that Au NPs with low sphericity can significantly enhance solar heating ability in the simulation cases.

Optical Data Storage and Multicolor Emission Readout on Flexible Films Using Deep‐Trap Persistent Luminescence Materials

AbstractThe 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.

Epoxy‐Based Azopolymers with Enhanced Photoresponsive Properties Obtained by Cationic Homopolymerization

AbstractAzopolymers are highly versatile materials due to their unique photoresponsive properties. In this contribution, a novel azo‐modified epoxy network is synthesized by cationic homopolymerization with boron trifluoride monoethylamine (BF3.MEA) complex as initiator. The effect of the addition of a fixed content of amino‐functionalized azo chromophore, Disperse Orange 3, into the polymer matrix is studied in detail. First of all, the thermal curing cycle is optimized by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) measurements. Then, the resulting bulk azo‐modified epoxy networks are characterized by means of thermogravimetric analysis (TGA), FTIR, DSC, UV–vis spectroscopy, and rheological measurements. Finally, the optical response of thin films of these materials is determined. The results evidence that azo‐modified epoxy networks obtained by cationic polymerization with optimized curing cycle display high Tg values, high maximum photoinduced birefringence, fast writing speed, and exceptionally high remnant anisotropy. Therefore, this material is a promising candidate to be used for optical storage applications.

Continuous Hydrothermal Synthesis of Inorganic Nanoparticles: Applications and Future Directions.

Nanomaterials are at the leading edge of the emerging field of nanotechnology. Their unique and tunable size-dependent properties (in the range 1-100 nm) make these materials indispensable in many modern technological applications. In this Review, we summarize the state-of-art in the manufacture and applications of inorganic nanoparticles made using continuous hydrothermal flow synthesis (CHFS) processes. First, we introduce ideal requirements of any flow process for nanoceramics production, outline different approaches to CHFS, and introduce the pertinent properties of supercritical water and issues around mixing in flow, to generate nanoparticles. This Review then gives comprehensive coverage of the current application space for CHFS-made nanomaterials including optical, healthcare, electronics (including sensors, information, and communication technologies), catalysis, devices (including energy harvesting/conversion/fuels), and energy storage applications. Thereafter, topics of precursor chemistry and products, as well as materials or structures, are discussed (surface-functionalized hybrids, nanocomposites, nanograined coatings and monoliths, and metal-organic frameworks). Later, this Review focuses on some of the key apparatus innovations in the field, such as in situ flow/rapid heating systems (to investigate kinetics and mechanisms), approaches to high throughput flow syntheses (for nanomaterials discovery), as well as recent developments in scale-up of hydrothermal flow processes. Finally, this Review covers environmental considerations, future directions and capabilities, along with the conclusions and outlook.

Tight focusing of radially polarized circular Airy vortex beams

Tight focusing properties of radially polarized circular Airy vortex beams (CAVB) are studied numerically. The light field expressions for the focused fields are derived based on vectorial Debye theory. We also study the relationship between focal profiles, such as light intensity distribution, radius of focal spot and focal length, and the parameters of CAVB. Numerical results demonstrate that we can generate a radially polarized CAVB with super-long focal length, super-strong longitudinal intensity or subwavelength focused spot at the focal plane by properly choosing the parameters of incident light and high numerical aperture (NA) lens. These results have potential applications for optical trapping, optical storage and particle acceleration.

Ferroelastic modulation and the Bloch formalism.

The key to the development of advanced materials is to understand their electronic structure-property relationship. Utilization of this understanding to design new electronic materials with desired properties led to modern epitaxial growth approaches for synthesizing artificial lattices, which for almost half a century have become the mainstay of electronic and photonic technologies. In contrast to previous scalar modulation approaches, we now study synthetic crystal lattices that have a tensor artificial modulation and develop a theory for photons and conduction band states in these lattices in a regime with an unusual departure from the familiar consequences of translational symmetry and Bloch's theorem. This study reveals that a nonmagnetic crystal lattice modulated by a purely geometrical orientational superlattice potential can lead to localized states or to spiral states for electrons and photons, as well as weakly or strongly localized states that could be used to markedly slow down the propagation of light and for optical energy storage applications.