An imager pixel array capable of separating and detecting the spectral components of an incident light without the use of a color filter array. The imager pixel array employs a grating layer which allows one or more spectral components of incident light to be transmitted therethrough, but diffracts other spectral components of the incident light. Both the transmitted and diffracted spectral components can be sensed by photosensors in the imager pixel array and used in subsequent data processing, thereby improving the quantum efficiency of the imager device. The grating layer can be formed of first and second materials each having a refractive index which are substantially the same at a predetermined wavelength.