Embodiments of the invention present a system, method, etc. for illumination light in an immersion lithography stepper for particle or bubble detection. More specifically, embodiments herein provide an immersion lithography expose system comprising a wafer holder for holding a wafer, an immersion liquid for covering the wafer, an immersion head to dispense and contain said immersion liquid, and a light source adapted to lithographically expose a resist on the wafer. The system also comprises a light detector at a first location of the immersion head and a laser source at a second location within said immersion head.