Multiline oscillation of Q-switched cavity-dumped CO2 laser with intracavity diffraction grating

Extreme-ultraviolet (EUV) lithography employs a high-power short-pulse carbon dioxide (CO2) laser based on master oscillator power amplifier architecture to produce Sn plasma generating the EUV light. We demonstrate multiline oscillation of a CO2 laser with 20 ns of pulse duration for the master oscillator. An intracavity diffraction grating enables the 5-line oscillation (10.55, 10.57, 10.59, 10.61, and 10.63 mu m) by separating the different 5 lines spatially in a gas-discharge gain medium. The multiline CO2 laser employs a cavity length of 3000 mm and an electro-optically Q-switched cavity dumping to generate 20-ns laser pulses. The maximum output power is 10.6 W at 100-kHz repetition rate and the output stability is +/- 1.2% at 3 sigma over 30 minutes. The grating combines the separated 5 optical axes into one optical axis inside the cavity, which realizes the nearly single-mode (TEM00) oscillation with similar to 1.1 of M-2.