Electromagnetic analysis of the IR sensor focal plane arrays of micro-optics

Matrices of binary micro-lenses monolithically integrated with the focal-place-arrays (FPA) of longwave IR uncooled detectors can significantly improve sensor's parameters. Surface relief of the binary micro-lenses is built of annular stair step structures of heights and widths smaller than the radiation length. Scalar diffraction theory cannot correctly describe diffraction on these micro-structures and therefore the rigorous electromagnetic theory should be applied. In this aper, we have applied the electromagnetic eignemode method to study binary micro-optics for the longwave IR FPA of 50 micrometers pixel width. We have shown that binary refractive micro-lenses outperform their diffractive counterparts allowing for detectors of 10 micrometers width. The effective refractive micro-lenses require the 8-level surface relief. Geometrical optics predictions of the focal position agree quite well width electromagnetic calculations.