Laser Beam “Clean-Up” with Spatial Filter

To obtain good beam quality is important for many laser applications, and a typical experimental method to obtain good beam quality is the spatial filtering. Within a spatial filtering system, a pinhole is placed on the intermediate focal plane (i.e. the Fourier plane) to get rid of the unwanted spatial frequency components. To model such systems, one must consider the diffraction from the pinhole and the diffraction property of the laser beams, and we demonstrate the spatial filtering effect in this example.