Angle-Sensing, Bio-Inspired Photodetectors

A group of researchers created a photodetector that can detect the angle of incoming light. The detector, inspired by geckos’ directional hearing, measures the light intensity and incident angle. Lensless cameras, augmented reality, and robotic vision could all benefit from the technology.

A conventional imaging chip’s pixels can only detect light intensity and would typically need to be combined with bulky lenses to obtain this information. However, as imaging systems become smaller, pixel size approaches the optical wavelength, and conventional optical elements such as lenses cannot be miniaturized indefinitely without sacrificing accuracy. Angle-sensitive subwavelength pixels are thus a very appealing prospect for advanced imaging applications, according to the team.

Geckos have such small ears that they must triangulate sound using a tiny tunnel through their heads. Soundwave coupling between the two ears allows for angle sensing. Geckos’ ears are so close together that it’s like having two eyes trying to figure out where the light is coming from.

The researchers discovered that the same phenomenon that allows a gecko to triangulate sound could also be used to triangulate light. The researchers used an analogous structure in their photodetector by lining up two silicon 100-nm nanowires side by side, mimicking the eardrums of a gecko. Gold electrodes cover the ends of each nanowire, forming two electrically isolated but optically coupled photodetectors.

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