RMIT researchers have developed a device that allows the future development of an ultrafast information processing platform for large scale optical computing.
Optical computing promises to deliver processing performance exponentially faster and more powerful than today's digital electronic microprocessors.
To make this technology a reality, however, photonic information processing platforms must first become at least as efficient at multi-tasking as the microprocessors they are designed to replace.
By applying some of the advantages of visible or infrared networks at the device and component scale, RMIT researchers from the School of Engineering have developed an ultrafast on-chip photonic information processing platform to encode and manipulate photons in an infinite number of ways.
Dr Jiao Lin, Vice Chancellor Research Fellow in the School of Engineering, collaborated with colleagues from La Trobe University, The University of Melbourne, Nanyang Technological University (Singapore), A*STAR (Singapore) and Shenzhen University (China) to use surface plasmon polaritons (SPPs) to reduce the dimension of the photonic device, and increase the speed of optical Fourier Transform (FT) by four to five orders of magnitude.
According to Lin FT is a cornerstone of optical processing, a method for representing an irregular signal as a combination of pure frequencies.
"It’s universal in signal processing, but it can also be used to compress image and audio files, solve differential equations and price stock options, among other things," he said.
"Optical Fourier transforms can be performed on a chip by using SPPs, which are infrared or visible-frequency electromagnetic waves that involve both charge motion in the metal and electromagnetic waves in the air.
"Visible-light and infrared beams, unlike electric currents, pass through each other without interacting but a converging lens performs an optical FT in free space when light passes through it.
"In addition, the speed of the transformation is limited by the thickness and the focal length of the lens.
"Unlike performing optical Fourier transforms via lenses in free space, the SPP approach needs a propagation distance of just 10 microns, dramatically reducing the physical footprint and increasing the speed of optical information processing by four to five orders of magnitude."
The team demonstrated the feasibility of the approach using a chip made from silica substrate coated with a 300-nm-thick layer of silver, which had a series of milled subwavelength slits.
"Interestingly, SPPs excited by light from a Helium–Neon laser were shown to be Fourier transformed into beams on the chip", said Lin.
"In summary, we have established a Fourier relationship embedded in the propagation of surface waves, enabling the design of devices to be incorporated into existing integrated optics, marking another step toward on-chip optical computing."
The discovery could open up opportunities for applications in photonic data storage, light generation, biophotonics enabling subwavelength optics in microscopy and lithography beyond the resolution limit of an optical imaging system.
The findings have been published in the scientific journal Light: Science & Applications (Nature Published Group).
The next phase in its development will be to scale-up its function and capacity, then prove the technology for use in the realms of optical computing through partnership with industry.
Story: Petra van Nieuwenhoven