Efficient colour splitters for high-pixel-density image sensors

• Published in: Nature photonics Vol. 7; no. 3; pp. 240 - 246
• Main Authors: Nishiwaki, Seiji, Nakamura, Tatsuya, Hiramoto, Masao, Fujii, Toshiya, Suzuki, Masa-aki
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.03.2013; Nature Publishing Group
• Subjects: 639/624/1107/510; Applied and Technical Physics; Arrays; Color; Colors (materials); Colour; Filtering; Light; Photonics; Photons; Physics; Pixels; Quantum Physics; Sensors; Silicon nitride; Japan
• ISSN: 1749-4885; 1749-4893
• DOI: 10.1038/nphoton.2012.345

When the pixel size of image sensors shrinks to the wavelength of light, this results in low signal levels for a given photon flux per pixel as a result of scaling laws. Because many image sensors require colour filters, it becomes crucial for small-pixel sensors to have an efficient filtering method that can capture all incident photons without absorbing them. Here, we propose a new method to split colours by using a microscale plate-like structure with a transparent medium that has a higher refractive index than the surrounding material. We experimentally demonstrate that this principle of colour splitting based on near-field deflection can generate colour images with minimal signal loss. From comparisons of the sum of the total integrated values for the colour channels, we confirm the amount of light received is 1.85 times that of the conventional colour filter method of the Bayer array, while maintaining the same level of resolution. Colour filters that split light by employing near-field interference effects instead of absorption provide enhanced signal levels for dense, small-pixel image sensors.