The present invention relates to a system for recirculating the gas atmosphere within an excimer laser system, where contaminates, created in the laser's operation, are removed, and the gas concentrations of additive gases, such as Xe, Kr, or others, depleted in the laser operation, are rebalanced to specific lazing mixtures by analyzation and component replenishment from one or more external supplies.

An apparatus includes: abeam splitter on abeam path, the beam splitter configured to receive light from a deep ultraviolet (DUV) light source; and a first plurality of reflective optical elements on the beam path. The beam splitter is configured to direct a portion of the light received from the DUV light source toward the first plurality of reflective optical elements; the first plurality of reflective optical elements is configured to rotate a divergence of the portion of the light to produce rotated light; and the beam splitter is configured to direct the rotated light and a portion of the light received from the DUV light source onto an output beam path.

A laser system includes a laser radiation source for providing pulsed laser radiation, and an optical system that includes a first polarization setting optical unit configured to set a circular polarization state of the pulsed laser radiation and a multipass cell having at least two mirrors. The pulsed laser radiation passes through the multipass cell with formation of a plurality of intermediate focus zones. The multipass cell is filled with a filling gas that has an optical nonlinearity and causes a spectral broadening of the pulsed laser radiation in the intermediate focus zones. A pressure of the filling gas is set in a pressure range so that there is an ionization behavior of the filling gas in a form of multiphoton ionization. Focus diameters of the intermediate focus zones are set such that the pulsed laser radiation passes through the multipass cell without ionization of the filling gas.

A light source apparatus (200) includes a gas discharge stage (210) and a metal fluoride trap (300). The gas discharge stage includes an optical amplifier (206) and a set of optical elements (250, 260). The optical amplifier includes a chamber (211) configured to hold a gas discharge medium (213), the gas discharge medium outputting a light beam. The set of optical elements is configured to form an optical resonator around the optical amplifier. The metal fluoride trap is configured to trap metal fluoride dust generated from the gas discharge stage. The metal fluoride trap includes an electrostatic precipitator (320) and a packed-bed filter (400, 402, 404) disposed around the electrostatic precipitator. The packed-bed filter includes a plurality of beads configured (406, 408) to absorb metal fluoride dust (208).