Optical Setup for differential wavefront sensing
Typically, measuring or calibrating the stage movement in three degrees of freedom (DOF) requires three different setups. However, we have developed a 3-DOF fiber-delivered heterodyne interferometer which uses a single beam to simultaneously measure target displacement and changes in pitch and yaw. This interferometer applies differential wavefront sensing where each DOF can be decoupled and measured from phase information of the quadrant photodiode. Analytical models and simulations are currently being developed and experiments will be performed to validate how the beam diameter, beam aberrations, detector size, and beam centroid mismatch affect DWS.