Polarization-multiplexed optical memory with urethane-urea copolymers

Sub-Diffraction Readout Method of High-Capacity Optical Data Storage Based on Polarization Modulation

The big data era demands an efficient and permanent data storage technology with the capacity of PB to EB scale. Optical data storage (ODS) offers a good candidate for long-lifetime storage, as the developing far-field super-resolution nanoscale writing technology improves its capacity to the PB scale. However, methods to efficiently read out this intensive ODS data are still lacking. In this paper, we demonstrate a sub-diffraction readout method based on polarization modulation, which experimentally achieves the sub-diffraction readout on Disperse Red 13 thin film with a resolution of 500 nm, exceeding the diffraction limit by 1.2 times (NA = 0.5). Differing from conventional binary encoding, we propose a specific polarization encoding method that enhances the capacity of ODS by 1.5 times. In the simulation, our method provides an optical data storage readout resolution of 150 nm, potentially to 70 nm, equivalent to 1.1 PB in a DVD-sized disk. This sub-diffraction readout method has great potential as a powerful readout tool for next-generation optical data storage.

Five-Dimensional Optical Data Storage Based on Ellipse Orientation and Fluorescence Intensity in a Silver-Sensitized Commercial Glass

Five-dimensional (5D) recording and decoding is demonstrated by using femtosecond direct laser writing in a silver-containing commercial glass. In particular, laser intensities and ellipse orientations generated by anamorphic focusing are employed to produce 5D data storage unit (3D for XYZ, 1D for the orientation of the elliptically-shaped data storage unit and 1D for its fluorescence intensity). In the recording process, two different images of a 4-bit bitmap format were simultaneously embedded in the medium by multiplexing the elliptical orientation of the laser focus and its intensity so as to access oriented elliptical patterns with independent fluorescence intensity. In the decoding process, two merged original images were successfully reconstructed by comparing each data storage unit with a fabricated calibration matrix of 16 × 16 levels for elliptic orientations and fluorescence intensities. We believe this technique can be applied to semi-permanent high-density data storage device.

Structural colour QR codes for multichannel information storage with enhanced optical security and life expectancy

Current schemes for encoding and decoding anticounterfeiting optical quick response (QR) codes involve miscellaneous challenges. The need for using multiple light sources to read out the wavelength-multiplexed data from optically encoded organic dyes, photoblinking from quantum dots, and autofluorescence from carbon dots are some typical examples. In order to address these restrictions, we exploited our previously devised nanoimprinting-exposure-thermal-treatment (NETT) data storage approach to present a new structural-colour-based regime for optical encoding of high-security QR codes. The angle-dependent readability of our diffraction-based nanostructures poses an enhanced optical security feature that can substitute the existing inefficient encoding strategies by eliminating the constraints associated with them. Additionally, in comparison with conventional optical encoding media, using the long-lasting photocrosslinked SU-8 in the NETT method considerably enhances the life expectancy of the proposed QR codes. Also, considering the rapid NETT-based Ni stamp origination method, which was previously introduced by our group, mass-generation of the proposed codes is feasible. Owing to the special optically variable effects provided by the nanostructures, duplication of our QR codes is very difficult. The colour code design, which embeds 766 characters in 2907 modules in red, green and blue channels, was generated and fabricated onto generic nanostructure arrays using the NETT process. The encoded information was successfully read out from the pattern using a broadband light source and a digital camera. Higher capacities are also deemed to be reachable by implementing image processing and machine learning algorithms to overcome in-channel module recognition and cross-channel interferences.

Polarization-multiplexed encoding at nanometer scales

Optical data storage was developed using binary encoding primarily due to signal to noise ratio considerations. We report on a multiplexing method that allows a seven fold storage increase, per storage layer, per side, and propose one that can yield theoretically a 20+ fold increase. Multiplexing is achieved by encoding information in polarization via appropriately oriented nanostructures that emit strongly polarized light when excited by unpolarized light. The storage increase is possible due to the significantly reduced crosstalk that results form using unpolarized light.

Jitter-free multi-layered nanoparticles optical storage disk with buffer ring

A multi-layered nanoparticles optical disk has been developed for a jitter-free high-density data storage system. The disk has nano structures composed of 300-nm-diameter photosensitive particles and 30-nm-width non-photosensitive buffer rings around them. With the buffer rings into the nanoparticles disk, a conventional confocal microscope equipped with a low numerical aperture (NA) objective picked up a particle's shape signal to generate a synchronous signal on its own. In the three-dimensional structured disk proposed, no electronically-produced reference signal is necessary for clock data recover (CDR); no jitter occurs in data decoding.

Infochemistry: encoding information as optical pulses using droplets in a microfluidic device

This article describes a new procedure for generating and transmitting a message--a sequence of optical pulses--by aligning a mask (an opaque sheet containing transparent "windows") below a microfluidic channel in which flows an opaque continuous fluid containing transparent droplets. The optical mask encodes the message as a unique sequence of windows that can transmit or block light; the flow of transparent droplets in the channel converts this message into a sequence of optical pulses. The properties of the windows on the mask (e.g., their size, wavelength of transmittance, orientation of polarization) determine the information carried in these optical pulses (e.g., intensity, color, polarization). The structure of a transmitted signal depends on the number and spacing of droplets in the channel. Fourier transformation can deconvolve superimposed signals created by the flow of multiple droplets into the message that a single droplet would transmit. The research described in this contribution explores a new field at the intersection of chemistry, materials science, and information technology: infochemistry.

Five-dimensional optical recording mediated by surface plasmons in gold nanorods

Multiplexed optical recording provides an unparalleled approach to increasing the information density beyond 10(12) bits per cm(3) (1 Tbit cm(-3)) by storing multiple, individually addressable patterns within the same recording volume. Although wavelength, polarization and spatial dimensions have all been exploited for multiplexing, these approaches have never been integrated into a single technique that could ultimately increase the information capacity by orders of magnitude. The major hurdle is the lack of a suitable recording medium that is extremely selective in the domains of wavelength and polarization and in the three spatial domains, so as to provide orthogonality in all five dimensions. Here we show true five-dimensional optical recording by exploiting the unique properties of the longitudinal surface plasmon resonance (SPR) of gold nanorods. The longitudinal SPR exhibits an excellent wavelength and polarization sensitivity, whereas the distinct energy threshold required for the photothermal recording mechanism provides the axial selectivity. The recordings were detected using longitudinal SPR-mediated two-photon luminescence, which we demonstrate to possess an enhanced wavelength and angular selectivity compared to conventional linear detection mechanisms. Combined with the high cross-section of two-photon luminescence, this enabled non-destructive, crosstalk-free readout. This technique can be immediately applied to optical patterning, encryption and data storage, where higher data densities are pursued.

Rewritable polarization-encoded multilayer data storage in 2,5-dimethyl-4-(p-nitrophenylazo)anisole doped polymer

We report a rewritable polarization-encoded multilayer data storage method with a polymer film doped with the azo dye DMNPAA (2,5-dimethyl-4-(p-nitrophenylazo)anisole). It is found that under two-photon excitation by a linearly polarized femtosecond laser beam at wavelength 780 nm the optical axis of DMNPAA molecules can be oriented to the perpendicular direction of the beam via a trans-cis-trans isomerization process. As a result, multilayer polarization-encoded optical data storage is demonstrated by recording two letters of a bit spacing of 4 microm in the same region of a given layer. It is shown that erasing and rewriting a particular layer is possible.

Three-dimensional imaging analysis of confocal and conventional polarization microscopes by use of Mie scattering theory

We present a three-dimensional imaging analysis of confocal and conventional polarization microscopes by using the extended Mie scattering theory. In the analysis, we calculate the images of a Mie particle whose diameter is comparable with the wavelength of confocal and conventional microscopes. It was found that, when we observe a Mie particle, polarization confocal microscopy is not affected by the polarization distortion that is due to focusing with high-numerical-aperture lenses and does not produce pseudopeaks in the images in comparison with conventional polarization microscopy. The three-dimensional resolution of the polarization microscope and the verification of the proposed analysis method are also discussed.