Optical modeling of MEMS corner cube retroreflectors withmisalignment and nonflatness

摘要

Micromachined corner cube retroreflectors (CCRs) can be employednas transmitters in free-space optical communication links. In thisnapplication, a CCR is illuminated by an unmodulated beam, and one mirrornof the CCR is intentionally misaligned to modulate the intensity of thenretroreflected beam. The low power consumption, small size, and ease ofnoperation of a CCR makes it an attractive option for certain types ofnoptical links. However, curvature and misalignment of the micromachinednmirrors can cause CCRs to perform far from theoretical limits. In thisnpaper, we develop two methods to predict the optical performance of CCRsnhaving ideal or nonideal mirrors. We first introduce a discretizednanalysis method based on ray tracing and scalar diffraction theory. Wenthen propose a simpler phase-shift model under the assumptions that thenmisalignment and surface nonflatness are small and that they do notnalter the optical topology of the CCR. These assumptions are satisfiednby typical CCRs to be used in free-space optical links. Using our twonmethods, we determine tolerances on mirror curvature and misalignmentnfor representative micromachined CCRs