Plasmonic angle sensitive pixel for digital imagers

A new method for making angle sensitive pixels (ASP) is proposed and simulated. Although the angle-sensitive properties of plasmonic gratings are well known, this is the first component to provide the necessary additional features to allow that sensitivity to be exploited for making ASP. Our ASP comprises an optical plasmonic grating (a lateral momentum filter) that is aperture-coupled to an interference filter. Together, the two filters will only pass light within a narrow range of wavelengths, that is arriving from within a narrow range of angles. To illustrate the concept, an example pixel is simulated using finite difference time domain. The metal is modelled as aluminium so as to be compatible with CMOS foundries. The unoptimised example shows 6 per cent transmission of 525 nm light arriving at -15 degrees from the normal. The full-width-half maximum of the pass band is 100 nm, suggesting a 3 degree acceptance angle. Smaller acceptance angles can be obtained by altering the grating profile. Possible applications include adding depth perception to a lensed imaging system, and imaging without lenses, although the details of these schemes are outside the scope of this Paper.