ACTIVE SPECTRAL CONTROL OF DUV LIGHT SOURCE

A line narrowed high average power high pulse repetition laser micro-photolithography light source bandwidth control system comprising: a bandwidth metrology module measuring the bandwidth of a laser output light pulse beam produced by the light source and providing a bandwidth measurement; a bandwidth error signal generator receiving the bandwidth measurement and a bandwidth setpoint and providing a bandwidth error signal; a multi-stage actuator system comprising: a coarse bandwidth correction actuator adapted to induce a first modification of the light source that influences the bandwidth of the laser output light pulse beam and targeting large amplitude disturbances occurring at low frequency; a fine bandwidth correction actuator adapted to induce a second modification of the light source that influences the bandwidth of the laser output light pulse beam and targeting small amplitude disturbances occurring at high frequency; an active bandwidth controller providing a fine bandwidth correction actuator signal to said fine bandwidth correction actuator and a coarse bandwidth correction actuator signal to said coarse bandwidth correction actuator responsive to the bandwidth error signal.