A line narrowed high average power high pulse repetition laser micro-photolithography light source bandwidth control system comprising: a bandwidth metrology module configured to measure the bandwidth of a laser output light pulse beam pulse produced by the light source and to provide a bandwidth measurement; a bandwidth error signal generator configured to receive the bandwidth measurement and a bandwidth setpoint and to provide a bandwidth error signal; a fine bandwidth correction actuator; an active bandwidth controller configured to calculate a fine bandwidth correction actuator signal based on the bandwidth error signal provided by the bandwidth error signal generator, and to provide the fine bandwidth correction actuator signal to the fine bandwidth correction actuator; said fine bandwidth correction actuator comprises a relative time delay controller for controlling a relative time delay between commutation of a master oscillator pulse power supply and a power amplifier or power oscillator pulse power supply of said laser micro-photolithography light source or a grating curvature controller for controlling a curvature of a grating in a line narrowing module of said laser micro-photolithography light source, characterised in that said system further comprises a coarse bandwidth correction actuator comprising a fluorine injection controller adapted for adjusting a fluorine concentration in a laser chamber of said laser micro-photolithography light source; wherein the coarse bandwidth correction actuator is configured to operate on a first laser component to adjust the bandwidth of the laser output light pulse beam on a first time scale and the fine bandwidth correction actuator is configured to operate on a second laser component that is different from the first laser component to adjust the bandwidth of the laser output light pulse beam on a second time scale that is faster than the first time scale; and wherein the active bandwidth controller is configured to calculate a coarse bandwidth correction actuator signal based on the bandwidth error signal provided by the bandwidth error signal generator, and to provide the coarse bandwidth actuator signal to the coarse bandwidth correction actuator. a bandwidth metrology module configured to measure the bandwidth of a laser output light pulse beam pulse produced by the light source and to provide a bandwidth measurement; a bandwidth error signal generator configured to receive the bandwidth measurement and a bandwidth setpoint and to provide a bandwidth error signal; a fine bandwidth correction actuator; an active bandwidth controller configured to calculate a fine bandwidth correction actuator signal based on the bandwidth error signal provided by the bandwidth error signal generator, and to provide the fine bandwidth correction actuator signal to the fine bandwidth correction actuator; said fine bandwidth correction actuator comprises a relative time delay controller for controlling a relative time delay between commutation of a master oscillator pulse power supply and a power amplifier or power oscillator pulse power supply of said laser micro-photolithography light source or a grating curvature controller for controlling a curvature of a grating in a line narrowing module of said laser micro-photolithography light source, characterised in that said system further comprises a coarse bandwidth correction actuator comprising a fluorine injection controller adapted for adjusting a fluorine concentration in a laser chamber of said laser micro-photolithography light source; wherein the coarse bandwidth correction actuator is configured to operate on a first laser component to adjust the bandwidth of the laser output light pulse beam on a first time scale and the fine bandwidth correction actuator is configured to operate on a second laser component that is different from the first laser component to adjust the bandwidth of the laser output light pulse beam on a second time scale that is faster than the first time scale; and wherein the active bandwidth controller is configured to calculate a coarse bandwidth correction actuator signal based on the bandwidth error signal provided by the bandwidth error signal generator, and to provide the coarse bandwidth actuator signal to the coarse bandwidth correction actuator.