An optical element may include {HEAD ~ a first diffractive structure} having {TAIL ~ a radially symmetric amplitude function} and a second diffractive structure having a phase function 
having
An optical element may include { HEAD ~ a first diffractive structure } having { TAIL ~ a radially symmetric amplitude function } and a second diffractive structure having a phase function
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH