Access Optical Networks says it has developed a 1.2TB holographic storage cube that can transfer data at 155MB/sec and last longer than 50 years. Oh, and it's done using mirrors – but no smoke.
The storage medium is a 1cm cube of photorefractive lithium niobate crystalline material and the claimed cost/GB is $0.11 in 1,000 unit quantities.
AON is reported by Laser Focus World to be storing digitised and parallel data in 1,000 x 1,000 arrays inside a crystal volumetric space. Readout uses CMOS cameras and there is parallel reading and writing of 1 million bits at a time.
AON says there is a greater than an order of magnitude layer depth in its holographic crystal cubes compared to holographic disks such as the unfortunately defunct Inphase Tapestry 300GB drive.
It works like this: a coherent laser source sends out its light beam, which is then divided into data and reference beams taking separate paths to the cube destination. The reference beam can be phase-controlled, enabling it to be switched on and off, writing and erasing all or parts of holograms. It can be made to adopt a selected multiplexed angle when writing, searching for or accessing a particular hologram. The greyscale-encoded holograms are written close to 900 for the most efficient diffraction.
The data beam is directed into the cube by being reflected from micro-mirrors on the surface of a MEMS (Micro-electrical-mechanical-system) spatial light modulator.
Cross-sectional schematic of three elements in a micro-machined spatial light modulator (Boston University).
The cube stores multiple holograms by angle multiplexing and data is written as data pages made up from clusters and sections. Data locations in the cube can be selectively erased for re-use. The removal of disk rotation means there is much less need to cater for shock and vibration in the device.
AON says that holographic disks, which are spindle-based media, are slow at reading and writing and are typically write-once-read-many (WORM) devices – which limits their usefulness, although it was a familiar form factor for optical disks and needed low-power lasers. A cube-based or volumetric approach enables higher hologram capacity: its performance is faster and it can be scaled higher.
AON's roadmap for the technology shows capacity growing to 9.6TB, and the transfer rate increasing to 1.24GB/sec. The company has a protected website with access requests made by email from its home page.
Its CEO and president, Glenn Gladney, says he is seeking strategic partners to collaborate with the company to complete the development of its technology. Isn't that always the way with new holographic technology?
Even though this cube looks to be a better holographic storage bet than any holo disk, venture capitalists like Bart Stuck, who backed InPhase, might need a fair amount of persuasion to open their wallets. It helps that Gadney says: "Our products offer a 300 K radiation-hardened storage medium that can be clean-erased in minutes."
Indeed, but they are not proper products yet and that is the problem. ®