Gas laser oscillator having auxiliary electrodes

A gas laser oscillator comprising:

• a plurality of laser gas circulation paths including a first path and a second path;
• a first discharge tube provided in the first path;
• a second discharge tube provided in the second path;
• a laser power supply for supplying a first high frequency power to the first discharge tube and supplying a second high frequency power having a different phase from the first high frequency power to the second discharge tube;
• and
• a matching unit including a first coil and a first capacitor to be used for impedance matching with a discharge load in the first path, and a second coil and a second capacitor to be used for impedance matching with a discharge load in the second path,
• wherein each value of the first coil, the first capacitor, the second coil, and the second capacitor is determined such that the difference between the peak value of a voltage applied to the first discharge tube and the peak value of a voltage applied to the second discharge tube falls within a predetermined range, and
• wherein an auxiliary electrode is provided in the vicinity of only one of the first discharge tube and the second discharge tube to which the voltage having the higher peak value is applied.