Light guide array for an image sensor

An image sensor pixel that includes a photoelectric conversion unit supported by a substrate and an insulator adjacent to the substrate. The pixel includes a cascaded light guide that is located within an opening of the insulator and extends above the insulator such that a portion of the cascaded light guide has an air interface. The air interface improves the internal reflection of the cascaded light guide. The cascaded light guide may include a self-aligned color filter having air-gaps between adjacent color filters. Air-gaps may be sealed from above by a transparent sealing film. The transparent sealing film may have a concave surface over the air-gap to diverge light that crosses the concave surface into the air-gap away from the air-gap into adjacent color filters. These characteristics of the light guide eliminate the need for a microlens. Additionally, a portion of a support wall between a pair of color filters may have a larger width above than below to form a necking to hold down the color filters for better retention.