Systems, methods, and computer programs for increasing a contrast for a lithography system are disclosed. In one aspect, a method of optimizing a process for imaging a feature on a substrate using a photolithography system is disclosed, the method including obtaining an optical spectrum of a light beam for the imaging, wherein the light beam includes pulses having a plurality of different wavelengths, and narrowing the optical spectrum of the pulses of the light beam for the imaging to improve a quality metric of the imaging.