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Full Name Comment goes here. Are you sure you want to Yes No. Be the first to like this. No Downloads. Views Total views. Actions Shares. Recently, inspired by a diffraction-unlimited far-field imaging approach, 38 scientists have developed super-resolution photoinduction-inhibition nanolithography SPIN , which can break the diffraction barrier and achieve 3D super-resolved writing. In contrast to conventional optical memory, SPIN is achieved by employing dual beams during recording; the behavior of each beam is still governed by its diffraction. One of the two beams, with a Gaussian shape, falls within the transition bands of the materials and thus is responsible for photoinduction.

The other beam, with a spatially modulated intensity distribution that is usually a doughnut shape with zero light intensity in the center , is responsible for inhibiting photoinduction everywhere in the focal region except at its center.

Introduction of Optical Disc Archive Library Systems

Consequently, the effective focal spot can be made much smaller than the diffraction barrier by the spatial superposition of the two beams and varying the intensity ratio between the two beams. Projection of the maximal capacity that a single disc can hold as a function of the feature size of the recorded bits.

In the projection, the lateral separation and the axial separation are set to 2. Top inset: comparison of direct laser recording and super-resolution recording by using SPIN methods. Bottom inset: comparison of conventional laser lithography and super-resolution lithography. SPIN, super-resolution photoinduction-inhibition nanolithography.

In general, photoinduction can refer to any photoinduced chemical or physical processes that initiate a change in material properties, such as photochromism, 39 photopolymerization 20 and photoreduction, 48 and that can also be terminated by an inhibition beam operating at a different wavelength.

In the meantime, sophisticated techniques for light manipulation on the focal plane are necessary to maintain an effective focal spot smaller than the diffraction limit with enriched physical dimensions. The combination of super-resolution techniques and multiplexing in the physical dimensions can further expand disc storage capacity beyond hundreds of PBs.

Three-Dimensional Optical Data Storage in Vitreous Silica - IOPscience

Comparison of the development of storage capacities using the HDD squares , flash triangles and ODS circles techniques. However, 5D storage has already broken the technical limitation of the HDD technique, achieving a capacity of 1. Another challenge confronting big data storage is low writing and reading throughputs.

Various optical parallelism methods for generating multifocal arrays in single laser shots have been proposed and experimentally demonstrated, including microlens arrays, 51 diffractive optical elements, 52 Debye-based Fourier transformation 53 and dynamic computer-generated holograms. Thus, polarization states of individual focal spots in 3D multifocal arrays have been controlled to achieve parallelism in the dimension of the polarization states.

As an example, the generation of cylindrically polarized multi-focal arrays has been demonstrated by applying the vectorial Debye-based Fourier transform method. The arrows indicate the polarization orientations. The physical dimensions of a writing beam can be used not only as information channels to increase the storage capacity but also as versatile means to encrypt information for data security, which is one of the most important aspects of any memory system.

As an electromagnetic wave, light can selectively interact with optical materials with physical anisotropic properties via its polarization, or the oscillation of its electric fields. The response of optical materials strongly depends on the orientation of the electric dipoles with respect to the polarization state of the light. As such, information can be encrypted using a specific polarization state of a writing beam, which cannot be retrieved without pre-knowledge of the polarization key.

By rotating the polarization orientation, flexibility of the encryption key can be achieved, and multiple states of information can be encrypted in the same spatial region. Information bits can be randomly accessed through the 2P fluorescence readout and retrieved in the diffraction mode of the recorded holograms.

Additionally, the enrichment of the physical dimensions for light—matter interactions offered by nanophotonic approaches enables information to be recorded in multimode material responses, which opens a new avenue toward a high level of information security.

Multi-dimensional Optical Storage

On the one hand, the information can be randomly accessed through two-photon fluorescence readout. On the other hand, the information can be simultaneously encrypted in holograms, ensuring its integrity and durability. However, the experimental achievement of such a high level of security strongly depends on material properties of the recording medium, specifically, its deterministic responses to light with various characteristics. Nanotechnology that offers the ability to engineer and control material properties on the nanoscale may provide a solid platform for future ultrahigh-security optical storage.

As we have noted, magnetization-based HDD techniques have a limited lifetime of 2—5 years, and therefore, frequent data migration is needed to avoid potential data loss. In addition, ODS only consumes energy when the data are written or read out and does not consume any energy when the optical disc is in idle state. Clearly, optical technology greatly reduces the waste generated by frequent data migration, reduces the energy consumption in idle status and reduces the cost for the replacement of new units associated with short lifetimes. Reduction in the operational cost for a single ODS unit compared with that of a single HDD unit as a function of years elapsed.

Consequently, the development of ODS with ultralong lifetimes has been a subject of intensive research. Permanent laser-induced physical changes, such as voids in polymers 62 and glass materials, 63 provide an approach to long-lifetime storage without information degradation. The top-down nanocomposite approach offers an alternative method that may allow the development of SPIN methods to break the diffraction limit for ultrahigh capacity ODS with thousands of years of lifetime.

The question of how to store the vast amount of data generated each year completely and efficiently is an urgent challenge confronting current information technologies. Scientists must selectively store only a portion of these valuable data. The US national priority project to map the human brain to gain an understanding of the cell types present in the brain, how they are connected and how they communicate is expected to generate more than ZB of data.

It is impossible to store such a vast amount of information using current technologies, even the cloud computing and storage have emerged as technical solutions for future big data storage, in which PB data centers provide key enabling platforms. Because of the low capacity and high energy consumption of HDD techniques, the resources necessary to store large amounts of data require inordinate amounts of power and rack space.

A typical PB data center occupies a stadium-sized space, including the racks and cooling accessories, which represents a significant overhead for such a data center. According to the IDC report, 1 the annual electricity consumption and maintenance costs for such a PB data center based on HDD arrays could even surpass the cost of the hardware itself.

Recent advances in nanophotonics-based ODS have exhibited the ability to address the bottlenecks that confront current HDD techniques, including storage capacity, lifetime, energy consumption and data-transfer rates.

Current Trends in Multi-Dimensional Optical Data Storage Technology

The integration of a single nanophotonics-based ODS unit with PB-scale capacity into multiple-unit arrays will provide a new platform for EB-scale big data centers to cope with vast amounts of information being produced in the digital era. Combined with its green features in energy conservation, nanophotonics-enabled optical storage arrays OSAs hold the potential to switch from the current magnetization-based approach to big data storage to the use of optical discs. Big data centers with a capacity approaching EBs become possible using the new OSA technique without any increase in the infrastructure size of the data centers.

Most importantly, photonics has been heralded as a sustainable information technique to replace its current electronic- and magnetic-based counterparts for big data era. It is believed that optical chips will emerge in the following 5—10 years to replace electronic chips for ultrafast and ultralow-energy-consumption optical computing. The optical fiber has already replaced copper-based wires for ultrahigh speed and ultrahigh-energy-efficiency communication. Once that day comes, the efficient and complete storage of big data will affect every aspect of a normal person's life, including e-health, e-banking, e-education and e-defense.

It will completely change the way people consume and store information. The capacity of the entire array system is the product of the total number of PB units and the capacity of each single disc. In the meantime, each unit has the ability to write and read in optical parallelism to maximize the throughput. By switching the future big data centers to the approach of nanophotonics-enabled OSA, each single disc will be able to achieve PB capacity and will therefore replace one PB-scale data center based on HDD arrays.

Number of data centers based on HDD units red bars and OSA units green bars required to store the global information generated each year. Unlike its counterparts, OSA-based big data centers are fully compatible with the optical-fiber communication technique, which is ubiquitously used in big data centers. By removing the necessity of electrical-to-optical converters, the data transfer between remote terminations and storage media could be made even faster. In addition to the question of how to accommodate an explosively increasing amount of information in current storage devices, another major challenge confronting the current big data centers based on HDD arrays is the question of how to store information in an energy-efficient manner.

Because of the low areal density of present technology, current data centers must be built on arrays of thousands of HDDs in order to reach a capacity of PBs. Moreover, HDD arrays consume energy during both operating and idle states and produce a significant amount of heat, which must be dissipated by gigantic accessorial cooling systems that consume a tremendous amount of electricity.

On the other hand, the high energy consumption raises a number of serious concerns regarding the sustainability of big data centers, including the vast costs of the infrastructure and environment pollution as well as the ever-increasing cost of maintenance. By contrast, nanophotonics-enabled OSAs of ultrahigh capacity, approaching the PB scale in a single DVD-sized disc, can dramatically ameliorate these concerns.

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The ultrahigh capacity and compactness of OSAs can dramatically alleviate the costs for the infrastructures of such stadium-sized big data centers. Most importantly, OSAs do not consume energy, while they are in the idle state, which eliminates the necessity for cooling accessories. Taking as an example an electricity consumption of 1. Indeed, the OSA enabled by nanophotonic approaches can save trillions of kWh of electricity per annum on the infrastructure development of new data centers, as well as eliminate millions of tons of CO 2 emission for a greener future.

In addition, OSAs can significantly reduce the annual electricity consumption required to store vast amounts of information generated each year.

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For comparison, the OSA technique, with its ultralow energy consumption per writing cycle and zero consumption, while in the idle state, can significantly reduce the electricity consumption and increase the efficiency of energy usage. The electricity conserved in the year by switching to OSA techniques could be equivalent to one thousand times the US residential electricity consumption in The permanent archiving of information that is generated annually is another important aspect of big data storage.

Typically, data stored using HDD-array techniques must be migrated every 2 or 3 years to prevent data loss.