New research by Columbia Engineering demonstrates remarkable optical nonlinear behavior of graphene that may lead to broad applications in optical interconnects and low-power photonic integrated circuits. With the placement of a sheet of graphene just one-carbon-atom-thick, the researchers transformed the originally passive device into an active one that generated microwave photonic signals and performed parametric wavelength conversion at telecommunication wavelengths.
They have engineered a graphene-silicon device whose optical nonlinearity enables the system parameters (such as transmittance and wavelength conversion) to change with the input power level. Using different optical frequencies to tune the radio frequency, they found that the graphene-silicon hybrid chip achieved radio frequency generation with a resonant quality factor more than 50 times lower than what other scientists have achieved in silicon. The researchers also were able to observe that, by optically driving the electronic and thermal response in the silicon chip, they could generate a radio frequency carrier on top of the transmitted laser beam and control its modulation with the laser intensity and color.
Until recently, researchers could only isolate graphene as single crystals with micron-scale dimensions, essentially limiting the material to studies confined within laboratories. “The ability to synthesize large-area films of graphene has the obvious implication of enabling commercial production of these proven graphene-based technologies,” explains James Hone, associate professor of mechanical engineering, whose team provided the high quality graphene for this study. “But large-area films of graphene (is an allotrope of carbon) can also enable the development of novel devices and fundamental scientific studies requiring graphene samples with large dimensions. This work is an exciting example of both-large-area films of graphene enable the fabrication of novel opto-electronic devices, which in turn allow for the study of scientific phenomena.”
And now, the recent excellent work done by this group of Columbia researchers demonstrates that graphene is also unique electro-optical material for ultrafast nonlinear optical modulation when it is combined with silicon photonic crystal structures. This opens an important doorway for many novel optoelectronic device applications, such as