Lithographic system

A lithographic system comprising:

• a lithographic apparatus;
• a radiation source comprising a fuel emitter operable to provide a fuel target at a plasma formation region;
• and
• a laser system operable to provide a laser beam which is incident on the fuel target to generate EUV radiation which is used to expose substrates, wherein the laser system comprises:
• a seed laser, and
• a laser beam amplification system comprising a series of optical amplifiers and a controller,
• wherein the controller is configured to operate a final optical amplifier of the series of optical amplifiers at a power level less than a maximum power level of the final optical amplifier during exposure of an exposure area of a substrate.

A lithographic system comprising:

• a lithographic apparatus;
• a radiation source comprising a fuel emitter operable to provide a fuel target at a plasma formation region;
• and
• a laser system operable to provide a laser beam which is incident on the fuel target to generate EUV radiation which is used to expose substrates, wherein the laser system comprises:
• a seed laser, and
• a laser beam amplification system comprising a series of optical amplifiers and a controller,
• wherein the controller is configured to operate a final optical amplifier of the series at a power level, relative to a maximum power level, that is lower than power levels, relative to respective maximum power levels, of other optical amplifiers of the series.

A method of amplifying a laser beam used to generate EUV radiation during exposure of an exposure area of a substrate, the method comprising:

• receiving a laser beam;
• amplifying the laser beam using a series of optical amplifiers;
• and
• operating a final optical amplifier of the series at a power level less than a maximum power level of the final optical amplifier.

A method of amplifying a laser beam used to generate EUV radiation, the method comprising:

• receiving a laser beam;
• amplifying the laser beam using a series of optical amplifiers;
• and
• operating a final optical amplifier of the series at a power level, relative to a maximum power level, that is lower than power levels, relative to respective maximum power levels, of other optical amplifiers of the series.