Device for on-line control of output power of vacuum-UV laser

A molecular fluorine laser system, comprising:

• a discharge chamber filled with a laser gas mixture at least including molecular fluorine and a buffer gas;
• a plurality of electrodes in the discharge chamber connected to a discharge circuit for energizing the laser gas mixture;
• a resonator having the discharge chamber therein for generating an output beam;
• a sealed enclosure for providing a beam path for the beam that is substantially free of contaminant species so that the energy of the beam can reach an application process without substantial disturbance due to the presence of the contaminant species along said beam path;
• a detector coupled with the enclosure;
• diagnostic processing electronics;
• and
• at least one optical component within the enclosure, and
• wherein said beam interacts with said at least one optical component within said enclosure and is directed along a beam path within said enclosure that is protected from being substantially disturbed by said contaminant species, such that in operation of said laser system, said at least one optical component interacts with said beam which is directed from the at least one optical component along said beam path within said enclosure and substantially delivered along said beam path to said application process,
• wherein said at least one optical component separates a diagnostic beam from the output beam and separates a visible component from a VUV component of the diagnostic beam, so that the output beam substantially continues to the application process and the diagnostic beam is detected at the detector comprising substantially only the VUV component, whereby one or more parameters of the VUV portion of the output beam are monitored by the detector of the VUV component of the diagnostic beam and diagnostic processing by the diagnostic processing electronics.