An extreme ultraviolet light generating system comprising:
- a target supply unit configured to output a target toward a predetermined region;
- and
- a laser apparatus configured to output a pulse laser beam with which the target is irradiated,
- the laser apparatus including:
- a master oscillator configured to alternately repeat burst oscillation to perform output of the pulse laser beam at a predetermined repetition frequency and suspension of the burst oscillation to suspend the output of the pulse laser beam at the predetermined repetition frequency;
- an amplifier provided in an optical path of the pulse laser beam outputted from the master oscillator;
- a power source configured to supply electric power to the amplifier;
- an energy sensor configured to detect pulse energy of the pulse laser beam outputted from the amplifier;
- and
- a controller configured to control the power source such that an excitation intensity of the amplifier in a burst oscillation period performing the burst oscillation is a first excitation intensity,
- control the power source such that, if the predetermined repetition frequency is a first repetition frequency, an excitation intensity of the amplifier in a suspension period suspending the burst oscillation is a second excitation intensity equal to or lower than the first excitation intensity,
- control the power source such that, if the predetermined repetition frequency is a second repetition frequency higher than the first repetition frequency, the excitation intensity of the amplifier in the suspension period is a third excitation intensity lower than the second excitation intensity;
- and
- control the power source such that a ratio of the excitation intensity of the amplifier in the suspension period to the excitation intensity of the amplifier in the burst oscillation period is based on the repetition frequency, and the excitation intensity of the amplifier in the suspension period is based on the ratio of the excitation intensity of the amplifier in the suspension period to the excitation intensity of the amplifier in the burst oscillation period and based on the excitation intensity of the amplifier in the burst oscillation period, wherein
- the amplifier includes a first amplifier and a second amplifier positioned downstream from the first amplifier provided in an optical path of a pulse laser beam outputted from the first amplifier, and
- the controller:
- acquires the pulse energy detected by the energy sensor in a situation where the repetition frequency in the burst oscillation period and the excitation intensity of the amplifier in the suspension period are set and laser oscillation is performed;
- calculates, based on the pulse energy, the relationship between the repetition frequency in the burst oscillation period and the excitation intensity of the amplifier in the suspension period to store the relationship in the storage medium;
- and
- controls the power source such that a ratio of the excitation intensity of the first amplifier in the suspension period to the excitation intensity of the first amplifier in the burst oscillation period is lower than a ratio of the excitation intensity of the second amplifier in the suspension period to the excitation intensity of the second amplifier in the burst oscillation period.