This is another step inintegrating graphene into both optical and electronic devices all with theintent of making things smaller and faster. This shows us a range of avenues been explored.
We all can see the outcome of 3dvideo streaming to a holodeck like presentation environment. Here we get a taste of the challengespresently been faced.
It will be sooner than anyonereally imagines. It makes it hard for meto commit to present technology when I can see what is shortly coming down thepike.
Graphene optical modulators could lead to 500 Gigahertz communications
MAY 08, 2011
Shown is a scanning electron microscope (SEM)image magnifying the key structures of the graphene-based optical modulator.(Colors were added to enhance the contrast). Gold (Au) and platinum (Pt)electrodes are used to apply electrical charges to the sheet of graphene, shownin blue, placed on top of the silicon (Si) waveguide, shown in red. The voltagecan control the graphene's transparency, effectively turning the setup into anoptical modulator that can turn light on and off. (Ming Liu image)
A team of researchers, led by UC Berkeley engineering professorXiang Zhang, built a tiny optical device that uses graphene, a one-atom-thicklayer of crystallized carbon, to switch light on and off. Thisswitching ability is the fundamental characteristic of a network modulator,which controls the speed at which data packets are transmitted. The faster thedata pulses are sent out, the greater the volume of information that can besent. Graphene-based modulators could soon allow consumers to streamfull-length, high-definition, 3-D movies onto a smartphone in a matter ofseconds, the researchers said.
Graphene enables modulators that are incredibly compact and that potentiallyperform at speeds up to ten times faster than current technology allows. Thisnew technology will significantly enhance our capabilities in ultrafast optical communication andcomputing. This is the world’s smallest optical modulator, and the modulator indata communications is the heart of speed control.
The researchers layered graphene on top of a silicon waveguide to fabricateoptical modulators. The researchers were able to achieve a modulation speed of1 gigahertz, but they noted that the speed could theoretically reach as high as500 gigahertz for a single modulator.
Graphene-based modulators could overcome the space barrier of optical devices,the researchers said. They successfully shrunk a graphene-based opticalmodulator down to a relatively tiny 25 square microns, a size roughly 400 timessmaller than a human hair. The footprint of a typical commercial modulator canbe as large as a few square millimeters.
A graphene-based waveguide-integrated optical modulator.
Integrated optical modulators with high modulation speed, smallfootprint and large optical bandwidth are poised to be the enabling devices foron-chip optical interconnects.
Semiconductor modulators have therefore been heavily researched overthe past few years. However, the device footprint of silicon-based modulatorsis of the order of millimetres, owing to its weak electro-optical properties.Germanium and compound semiconductors, on the other hand, face the majorchallenge of integration with existing silicon electronics andphotonics platforms. Integrating silicon modulators with high-quality-factoroptical resonators increases the modulation strength, but these devices sufferfrom intrinsic narrow bandwidth and require sophisticated optical design; theyalso have stringent fabrication requirements and limited temperaturetolerances7.
Finding a complementary metal-oxide-semiconductor (CMOS)-compatiblematerial with adequate modulation speed and strength has therefore become atask of not only scientific interest, but also industrial importance. Here weexperimentally demonstrate a broadband, high-speed, waveguide-integratedelectroabsorption modulator based on monolayer graphene. By electrically tuningthe Fermi level of the graphene sheet, we demonstrate modulation of the guidedlight at frequencies over 1 GHz, together with a broad operation spectrum thatranges from 1.35 to 1.6 µm under ambient conditions.
The high modulation efficiency of graphene results in an active devicearea of merely 25 µm2, which is among the smallest to date. This graphene-basedoptical modulation mechanism, with combined advantages of compact footprint,low operation voltage and ultrafast modulation speed across a broad range of wavelengths,can enable novel architectures for on-chip optical communications.
While components based upon optics have many advantages over those thatuse electricity, including the ability to carry denser packets of data morequickly, attempts to create optical interconnects that fit neatly onto acomputer chip have been hampered by the relatively large amount of spacerequired in photonics.
Light waves are less agile in tight spaces than their electrical counterparts,the researchers noted, so photon-based applications have been primarilyconfined to large-scale devices, such as fiber optic lines.
“Electrons can easily make an L-shaped turn because the wavelengths in whichthey operate are small,” said Zhang. “Light wavelengths are generally bigger,so they need more space to maneuver. It’s like turning a long, stretch limoinstead of a motorcycle around a corner. That’s why optics require bulkymirrors to control their movements. Scaling down the optical device also makesit faster because the single atomic layer of graphene can significantly reducethe capacitance – the ability to hold an electric charge – which often hindersdevice speed.”
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