All-optical RAM to clear comms bottleneck

NTT shows off nanowatt optical memory

Japanese researchers are claiming a breakthrough in all-optical memory, one of the key bottlenecks remaining in the optical communications world.

The high throughput of optical communications systems brings its own problem: any function that can’t be performed in the optical domain demands an opto-electric conversion, creating a bottleneck in the system. This has put a premium on research into optical switching, amplification and signal regeneration.

Memory is a tough nut to crack, however: it demands that a photon’s state be captured, retained and read out – all without converting the signal back to electrons, and in a repeatable and cheap fashion.

The NTT researchers say they have created an ultra-low-power optical RAM using optical cavities that represent a 1 or 0 by either passing or blocking light. The memory cell uses a material based on an indium gallium arsenide strip buried in gallium arsenide.

It acts as a memory because the indium-gallium arsenide strip changes its refractive index when exposed to a laser. The light beam it’s trying to “remember” will be blocked or passed depending on the state of the strip. A second pulse of laser on the “control” strip reverses its state.

While it only retains state for about a microsecond, the researchers say that’s long enough for other system components to use the stored information (and four times the previous record for an all-optical memory). Importantly, they also say the optical cavity approach consumes very low power – according to the Nature Photonics abstract, 30 nW, which is “more than 300 times lower than the previous record”. ®

Bootnote: Proposals for optical memory have existed for a surprisingly long time. For example, this Wikipedia entry describes an approach using a loop of photo-emissive and photo-sensitive materials from the 1950s, as an attempt to solve the problems of memory speed in early computers. ®

Keep Reading

The good optics of silicon photonics: Light sailing serenely down a fibre

Column 15 years in the making. Out of the labs and into the real world: The 100Gbps Internet connection

Massive news, literally: Three super-boffins awarded Nobel Prize in physics for their black-hole breakthroughs

Congratulations to Sir Roger Penrose, Andrea Gehz, Reinhard Genzel

Captain, the computer has identified 250 alien stars that infiltrated our galaxy – actual science, not science-fiction

Neural network trained to spot emigrated suns in our Milky Way uncovers mysterious Nyx collective

UK college courses show decade-long surging interest in computer science – just as new intake was locked down

Well, what's an English degree gonna do when we're all strapped to PCs?

SpaceX cargo ship splashes down off Florida with science in tow – but what we want to know is how space wine tastes

It's been sloshing around the International Space Station for a while

RIP Freeman Dyson: The super-boffin who applied his mathematical brain to nuclear magic, quantum physics, space travel, and more

Video Science's civil rebel dies aged 96

Absolute mad lads are teaching physics to AI because how else will it learn to solve real-world problems (like humans)

Can't take over the galaxy if you don't know how it works, innit?

Broken lab equipment led boffins to solve a 58-year-old physics problem by mistake

The mystery of manipulating nuclear spins with electric fields could make it easier to build quantum computers in the future

Biting the hand that feeds IT © 1998–2021