Scientists at The City College of New York have devised a method that could amplify the optical data storage capacity within diamonds. This innovation involves multiplexing storage in the spectral domain. The study, conducted by Richard G. Monge and Tom Delord from the Meriles Group in CCNY’s Division of Science, is titled “Reversible optical data storage below the diffraction limit” and has been published in the journal Nature Nanotechnology.
According to Delord, a postdoctoral research associate at CCNY, the significance lies in the ability to store multiple distinct images in the same location within the diamond. This is achieved by employing lasers of slightly different colors to encode various information into different atoms within microscopic regions. He also suggests that if this technique can be extended to other materials or implemented at room temperature, it holds potential applications in computing that demand high-capacity storage.
b) Scanning confocal image under green excitation of a crystal section featuring multiple NVs. The insets on the sides display optical spectra of circled NVs upon the application of a protocol using red illumination of variable frequency. A NV-selective image is obtained with the 637 nm laser tuned to one of the Sz transitions (indicated by an arrow in each spectrum), revealing only the resonant NV− in the images. Laser powers are 1.6 mW and 2 µW at 532 and 637 nm, respectively.
c) NV− ionization protocol under strong optical excitation (210 µW) at 637 nm. MW1 (MW2) denotes microwave excitation resonant with the ms = 0 ↔ ms = −1 (ms = 0 ↔ ms = +1) transition in the ground state triplet, with the duration of the π-pulses being 100 ns. The bottom graph illustrates the relative NV− charge state population as a function of the ionization interval (τI) for a representative NV in the set. All experiments are conducted at 7 K. PL: photoluminescence; a.u.: arbitrary units; λ: wavelength; APD: avalanche photo-detector; kcts: kilo-counts.
(Nature Nanotechnology)
The research at CCNY concentrated on minuscule components within diamonds and comparable materials referred to as “Color centers.” These are essentially atomic imperfections capable of absorbing light, providing a foundation for what is known as quantum technologies.
In the words of Delord, the team at CCNY achieved precise control over the electrical charge of these color centers by employing a narrow-band laser and cryogenic conditions. This innovative approach enabled them to write and read minuscule bits of data at a much finer level than was previously attainable, even down to a single atom.
Optical memory technologies are constrained by the “Diffraction limit,” a measure of the minimum diameter to which a beam can be focused. This limit is approximately half the wavelength of the light beam, meaning, for instance, that green light would have a diffraction limit of 270 nm.
In essence, the use of a beam constrained by the diffraction limit presents limitations in achieving a writing resolution smaller than this limit. Any attempt to displace the beam less than the diffraction limit could interfere with existing data. Typically, optical memories enhance storage capacity by employing shorter wavelengths, such as the shift to the blue spectrum, exemplified by ‘Blu-ray’ technology.
The distinctive feature of the CCNY optical storage method lies in its ability to overcome the diffraction limit. This is achieved by leveraging subtle color (wavelength) variations between color centers situated closer together than the diffraction limit.
The process involves adjusting the laser beam to wavelengths that are slightly shifted, allowing it to remain in the same physical location while engaging with various color centers. This selective interaction facilitates the alteration of their charges, effectively enabling the writing of data with sub-diffraction resolution. Monge, a postdoctoral fellow at CCNY, provided insights into this aspect of the study, having been involved in the research during his Ph.D. studies at the Graduate Center, CUNY.
The distinctive feature of this method lies in its reversibility. Monge emphasized that it allows for an infinite number of write, erase, and rewrite cycles. While some other optical storage technologies offer similar capabilities, it’s uncommon, especially concerning high spatial resolution. Monge drew a comparison to a Blu-ray disk, highlighting that, unlike the typical case where you can write a movie onto it but can’t erase and write another one, this approach permits repeated alterations.
Resources
- ONLINE NEWS City College of New York. (2023, December 4). Optical data storage breakthrough increases capacity of diamonds by circumventing the diffraction limit. Phys.org. [Phys.org]
- JOURNAL Monge, R., Delord, T., & Meriles, C. A. (2023). Reversible optical data storage below the diffraction limit. Nature Nanotechnology. [Nature Nanotechnology]
Cite this page:
APA 7: TWs Editor. (2023, December 5). The Diffraction Limit: How to Bypass It and Increase the Optical Data Capacity of Diamonds? PerEXP Teamworks. [News Link]
