Ostensibly perpetual optical data storage in glass with ultra-high stability and tailored photoluminescence

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 2×10^(7)years is attained with single ultrafast laser pulse induced reduction of Eu^(3+)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/cm^(2).Furthermore,the active ions of Eu^(2+)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.

Near-perfect fidelity polarization-encoded multilayer optical data storage based on aligned gold nanorods

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 en-hancing 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-en-coding multilayer ODS technique for high-fidelity data recording and retrieving by utilizing a nanofibre-based nanocom-posite 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 im-proved the bit recall fidelity that is quantified by a correlation coefficient higher than 0.99.It is anticipated that the demon-strated technique can facilitate the development of multiplexing ODS for a greener future.

Decoding the future:opportunities and challenges in next-generation optical data storage[Invited]

The ongoing quest for higher data storage density has led to a plethora of innovations in the field of optical data storage.This review paper provides a comprehensive overview of recent advancements in next-generation optical data storage,offering insights into various technological roadmaps.We pay particular attention to multidimensional and superresolution approaches,each of which uniquely addresses the challenge of dense storage.The multidimensional approach exploits multiple parameters of light,allowing for the storage of multiple bits of information within a single voxel while still adhering to diffraction limitation.Alternatively,superresolution approaches leverage the photoexcitation and photoinhibition properties of materials to create diffraction-unlimited data voxels.We conclude by summarizing the immense opportunities these approaches present,while also outlining the formidable challenges they face in the transition to industrial applications.

Y_(3)Al_(5)O_(12):Ce^(3+) fluorescent ceramic for optical data storage

A kind of optical data storage medium based on electron-trapping materials,Y_(3)Al_(5)O_(12):Ce^(3+)fluorescent ceramic,was developed by vacuum sintering technology.The medium shows sufficiently deep traps[1.67 and 0.77 eV].The properties of trap levels were researched by thermoluminescence curves,and the optical storage mechanism based on Ce^(3+)ion doping was proposed.More importantly,the data can be written-in by 254 nm UV light,and readout by heating[300°C].This work expands the application fields of fluorescent ceramics,and it is expected to promote the development of electron-trapping materials.

Optical storage arrays: a perspective for future big data storage

The advance of nanophotonics has provided a variety of avenues for light–matter interaction at the nanometer scale through the enriched mechanisms for physical and chemical reactions induced by nanometer-confined optical probes in nanocomposite materials.These emerging nanophotonic devices and materials have enabled researchers to develop disruptive methods of tremendously increasing the storage capacity of current optical memory.In this paper,we present a review of the recent advancements in nanophotonics-enabled optical storage techniques.Particularly,we offer our perspective of using them as optical storage arrays for next-generation exabyte data centers.

Polarization readout analysis for multilevel phase change recording by crystallization degree modulation

Four different states of Si15Sb85 and Ge2Sb2Te5 phase change memory thin films are obtained by crystallization degree modulation through laser initialization at different powers or annealing at different temperatures. The polarization characteristics of these two four-level phase change recording media are analyzed systematically. A simple and effective readout scheme is then proposed, and the readout signal is numerically simulated. The results show that a high-contrast polarization readout can be obtained in an extensive wavelength range for the four-level phase change recording media using common phase change materials. This study will help in-depth understanding of the physical mechanisms and provide technical approaches to multilevel phase change recording.

Image edge-enhancement in optical microscopy with a phase mismatched spiral phase plate

We present a spiral phase filtering system with a large tolerance for edge enhancement of both phase and amplitude objects in optical microscopy.The method is based on a Fourier 4-f spatial filtering system.A phase mismatched spiral phase plate （SPP） fabricated by electron beam lithography is employed as the radial Hilbert transform for image edge enhancement.Compared with holography,SPP is simple,economical,reliable,and easy to integrate.

Fabrication of ordered micro- and nano-scale patterns based on optical discs and nanoimprint

A simple method to fabricate one-dimensional(1-D) and two-dimensional(2-D) ordered micro- and nano-scale patterns is developed based on the original masters from optical discs, using nanoimprint technology and soft stamps. Polydimethylsiloxane(PDMS) was used to replicate the negative image of the 1-D grating pattern on the masters of CD-R, DVD-R and BD-R optical discs, respectively, and then the 1-D pattern on one of the PDMS stamps was transferred to a blank polycarbonate(PC) substrate by nanoimprint. The 2-D ordered patterns were fabricated by the second imprinting using another PDMS stamp. Different 2-D periodic patterns were obtained depending on the PDMS stamps and the angle between the two times of imprints. This method may provide a way for the fabrication of complex 2-D patterns using simple 1-D masters.

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance （SPR） biosensors, novel highly sensitive SPR biosensors with Au nanopartieles and nanogratings enhancement have been proposed recently. But in practice, these structures have obvious disadvantages. In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parame- ters on the performance is investigated by using rigorous coupled wave analysis （RCWA）. Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters. The results indicate that significant sensitivity increase is associated with localized surface plasmons （LSPs） excitation mediated by nanoholes. Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves＇ width are obtained simultaneously under optimized structural parameters.

Efficient multi-wavelength lasers made of Nd:GdLuAG crystal

Owing to the small differences between the cross-sections of the four emission peaks around 1.3 μm, an efficient four-wavelength synchronous launched laser is demonstrated using a Nd：Gd Lu AG crystal. The laser has no special resonator design. The maximum output power is 4.28 W, which corresponds to a conversion efficiency of 45.6%. For the Q-switching, the laser operated in dual-wavelength mode, and the single pulse energy is maintained at ～80 μJ. By calculating the population inversion density, multi-wavelength emission characteristics in both continuous wave and Q-switching lasers are discussed.

Properties of the 3D photonic nanojet based on the refractive index of surroundings

We exhibit a three-dimensional （3D） photonic nanojet based on a dielectric microsphere irradiated by a plane wave with the finite-difference time-domain （FDTD） method. We investigate the influence of the refractive index of the surrounding on the properties of the nanojet by simulating the electric field distributions in it. The simulation results show that, by optimally choosing the size of the sphere and the ratio of the refractive indices of the sphere and the surrounding, the focus point can occur just on the surface of the sphere even if the refractive index of the surrounding is changed. Additionally, the peak amplitude of the nanojet increases with increasing the refractive index of the surrounding. However, the decay length and the jet width of the nanojet decrease simultaneously. These effects may have potential applications in observation or manipulation of nano-objects such as antibodies in biology. In nanojet-enabled optical data storage, the photonic nanojet may be also helpful for improving data-storage capacities and retrieval speed by controlling the field amplitude, the decay length, and jet width of the nanojet.

Write-once medium with BiO_x thin films for blue laser recording

BiOx films are prepared by reactive direct current （DC） magnetron sputtering from a metallic bismuth target in Ar ＋O2 with different O2/Ar ratios. It is found that the optical property of BiOx films is sensitive to O2/Ar ratios and the films deposited at O2/Ar ratio of 0.5 have the best reflectivity contrast under the same conditions. The structure and optical characteristics of the films are studied by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, and spectrophotometer. As revealed by investigations, the phase transition is mainly responsible for the change of optical properties. The static test results indicate that the BiO~ films have good writing sensitivity for blue laser beams. A high reflectivity contrast of about 52% at a writing power of 11 mW and writing pulse width of 800 ns is obtained. In addition, the films demonstrate good stability after being read for 10000 times.