IBM slows flow of light to accelerate silicon chips

Yorktown Heights (NY) - IBM researchers announced that they have developed a device that is capable of delaying the flow of light on a silicon chip, which is considered a critical milestone in creating silicon chips that leverage optical communications to achieve better performance. Photonics have been viewed as key technology to accelerate future chips for some time, as light signals are able to transfer more data at faster pace than electrical signals. However, controlling the speed of light, which includes temporarily holding light signals, is critical for such devices and still a difficult task for researchers. IBM claims to have developed a device capable of "buffering" light in a device small enough to fit on a silicon chip.

IBM said that its scientists were able to meet this size restriction and achieve the necessary level of control of the light signal by passing it through a "new form" of silicon-based optical delay line built of up to 100 cascaded "micro-ring resonators."

When the optical waveguide is curved to form a ring, light is forced to circle multiple times, delaying its travel. The optical buffer device based on this simple concept can briefly store 10 bits of optical information within an area of 0.03 mm2. That is equivalent to about ten percent of the storage density of a floppy disk and, according to IBM, represents "a great improvement" over previous results. This advancement could potentially lead to integrating hundreds of these devices on one computer chip, an important step towards on-chip optical communications.

According to IBM, the micro-ring resonators were built using a common complementary metal-oxide-semiconductor (CMOS) fabrication tools. IBM hopes that the new device could lead the way to on-chip integration of compact nano-photonic circuits for manipulating the light signals - similar to the manipulation of electrical signals in today's silicon chips. The fact that IBM was able to use a common CMOS fabrication line could indicates that cheap mass production of densely integrated optoelectronic chips comprising both photonic and electronic circuitry could be possible in the foreseeable future.

Other recently revealed photonic research include Intel's hybrid silicon laser chip, a chip that combines traditional electrical and future optical technologies. The company claims that the device announced in September of this year can also be built using the firm's, and can be built using standard CMOS manufacturing processes.

Intel's hybrid chip employs 36 lasers and 36 modulators on one die as well as a multiplexor to route light beams with varying wavelengths through optical fiber. Each laser is about 1 micron wide and 800 microns long, which compares to the width of a human hair of about 100 microns. Intel aims to combine the platform with a data receiver chip to build an integrated silicon photonic chip, which could be used on computer boards and serve as interconnect between busses, between PCs and networks.