Gratings are often written into photoresist by interference (superposition) of optical beams. In other words, the standing wave formed by the overlap of multiple plane waves produces a (useful) exposure pattern. In this problem consider a Si wafer coated with photoresist lying in the x-y plane. Four plane waves from an Argon ion laser (l=488nm) are directed onto the sample each at 45 degrees angle of incidence. One wave arrives parallel to the +x direction, a second arrives parallel to the -x direction, a third arrives parallel to the +y direction, and the fourth arrives parallel to the -y direction.
What is the pattern formed in the photoresist?