Radiation Source

A laser comprising:

• a seed laser for providing a seed laser beam;
• a beam splitter for receiving the seed laser beam from the seed laser;
• an optical amplifier for receiving the seed laser beam from the beam splitter and performing optical amplification;
• a first reflector located downstream of the optical amplifier, configured to direct the seed laser beam back through the optical amplifier and on to the beam splitter;
• and
• a second reflector located farther downstream of the beam splitter, configured to receive the seed laser beam from the beam splitter and to direct the seed laser beam back toward the beam splitter.

A method of generating laser radiation, the method comprising:

• directing a seed laser beam toward a beam splitter;
• the seed laser beam being directed by the beam splitter to an optical amplifier for optical amplification;
• after the seed laser beam has passed through the optical amplifier, directing the seed laser beam back though the optical amplifier for optical amplification, and then on to the beam splitter;
• the beam splitter directing the seed laser beam downstream, where the seed laser beam is then directed back toward the beam splitter.

A radiation source comprising:

• a nozzle configured to direct a stream of fuel droplets along a trajectory towards a plasma formation location;
• a laser configured to direct laser radiation at a fuel droplet at the plasma formation location to generate, in use, a radiation generating plasma;
• wherein the laser comprises:
• a seed laser configured to provide a seed laser beam;
• a beam splitter configured to receive the seed laser beam from the seed laser;
• an optical amplifier configured to receive the seed laser beam from the beam splitter and performing optical amplification;
• a first reflector located downstream of the optical amplifier, configured to direct the seed laser beam back through the optical amplifier and on to the beam splitter;
• and
• a second reflector located further downstream of the beam splitter, configured to receive the seed laser beam from the beam splitter and to direct at least a portion of the seed laser beam back toward the beam splitter.

A laser comprising:

• a seed laser configured to provide a seed laser beam;
• a beam splitter configured to receive the seed laser beam from the seed laser;
• an optical amplifier configured to receive the seed laser beam from the beam splitter and performing optical amplification;
• a first reflector located downstream of the optical amplifier, configured to direct the seed laser beam back through the optical amplifier and on to the beam splitter;
• and
• a second reflector located further downstream of the beam splitter, configured to receive the seed laser beam from the beam splitter and to direct the seed laser beam back toward the beam splitter.

A lithographic apparatus comprising, being in connection with, or connectable to, a radiation source or laser comprising:

• a seed laser configured to provide a seed laser beam;
• a beam splitter configured to receive the seed laser beam from the seed laser;
• an optical amplifier configured to receive the seed laser beam from the beam splitter and performing optical amplification;
• a first reflector located downstream of the optical amplifier, configured to direct the seed laser beam back through the optical amplifier and on to the beam splitter;
• and
• a second reflector located further downstream of the beam splitter, configured to receive the seed laser beam from the beam splitter and to direct the seed laser beam back toward the beam splitter.

A method of generating laser radiation, the method comprising:

• directing a seed laser beam toward a beam splitter;
• the seed laser beam being directed by the beam splitter to an optical amplifier for optical amplification;
• after the seed laser beam has passed through the optical amplifier, directing the seed laser beam back though the optical amplifier for optical amplification, and then on to the beam splitter;
• the beam splitter directing the seed laser beam downstream, where the seed laser beam is then directed back toward the beam splitter.