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Biomimetic photodetector 'sees' in color

September 14, 2014



By a News Reporter-Staff News Editor at VerticalNews Science -- Rice University researchers have created a CMOS-compatible, biomimetic color photodetector that directly responds to red, green and blue light in much the same way the human eye does.

The new device was created by researchers at Rice's Laboratory for Nanophotonics (LANP) and is described online in a new study in the journal Advanced Materials. It uses an aluminum grating that can be added to silicon photodetectors with the silicon microchip industry's mainstay technology, "complementary metal-oxide semiconductor," or CMOS.

Conventional photodetectors convert light into electrical signals but have no inherent color-sensitivity. To capture color images, photodetector makers must add color filters that can separate a scene into red, green and blue color components. This color filtering is commonly done using off-chip dielectric or dye color filters, which degrade under exposure to sunlight and can also be difficult to align with imaging sensors.

"Today's color filtering mechanisms often involve materials that are not CMOS-compatible, but this new approach has advantages beyond on-chip integration," said LANP Director Naomi Halas, the lead scientist on the study. "It's also more compact and simple and more closely mimics the way living organisms 'see' colors.

Biomimicry was no accident. The color photodetector resulted from a $6 million research program funded by the Office of Naval Research that aimed to mimic cephalopod skin using "metamaterials," compounds that blur the line between material and machine.

"With plasmonic gratings, not only do you get color tunability, you can also enhance near fields," Zheng said. "The near-field interaction increases the absorption cross section, which means that the grating sort of acts as its own lens. You get this funneling of light into a concentrated area.

"Not only are we using the photodetector as an amplifier, we're also using the plasmonic color filter as a way to increase the amount of light that goes into the detector," he said.

Keywords for this news article include: Rice University.

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