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 uses an aluminum grating that can be added to silicon photodetectors with CMOS technology.

A method for designing imaging sensors integrates light amplifiers and color filters directly into pixels. (B. Zheng/Rice University)

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.

The new approach is more compact and simple, and more closely mimics the way living organisms see colors. 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. Cephalopods like octopus and squid are masters of camouflage, but they are also color-blind and may detect color directly through their skin.

The color photodetector uses a combination of band engineering and plasmonic gratings, comb-like aluminum structures with rows of parallel slits. Color selection is performed by utilizing interference effects between the plasmonic grating and the photodetector’s surface.