Graded order-sorting filter for hyperspectral imagers and methods of making the same

A method for fabricating a filter for hyperspectral imagers, the method comprising:

• forming a tapered absorption filter on a first side of a substantially transparent substrate wafer,
• wherein the tapered absorption filter has a graded composition with a graded bandgap outwardly from the first side of the substantially transparent substrate wafer, the tapered absorption filter having a decreasing absorption coefficient of short wavelength light photons along a taper direction.

A method for fabricating a hyperspectral imager, the method comprising:

• forming a tapered absorption filter on a first side of a substantially transparent substrate wafer, the tapered absorption filter being tapered along a taper direction and having a graded composition of at least two constituents with a graded bandgap, the tapered absorption filter is substantially transparent to light photons for photon energies substantially less than the graded bandgap;
• and
• aligning a two-dimensional array of pixels substantially parallel to a second side of the substantially transparent substrate wafer with a gap in between.