Laser focussing module

A laser source comprising:

• a laser focusing system configured to be used in the EUV radiation source, the laser focusing system comprising:
• a first curved mirror configured to receive a laser beam from a beam delivery system and generate a first reflected laser beam;
• and
• a second curved mirror configured to receive the first reflected laser beam and generate a second reflected laser beam,
• wherein the second reflected laser beam is focused onto a target location in a vessel of the EUV radiation source,
• wherein the vessel comprises a collector mirror,
• wherein an angle between an optical axis of the second reflected laser beam and a horizontal axis is smaller than 25 degrees,
• wherein the horizontal axis is defined by the optical axis of the collector mirror,
• wherein the laser beam is received by one or more additional mirrors that redirect the laser beam towards the first curved mirror;
• and
• wherein the one or more additional mirrors are configured to overcome a difference in location between the received laser beam and the redirected laser beam, and to translate the laser beam in a substantially vertical direction.

An EUV radiation source comprising:

• a laser source comprising:
• a laser focusing system configured to be used in the EUV radiation source, the laser focusing system comprising:
• a first curved mirror configured to receive a laser beam from a beam delivery system and generate a first reflected laser beam;
• and
• a second curved mirror configured to receive the first reflected laser beam and generate a second reflected laser beam,
• wherein the second reflected laser beam is focused onto a target location in a vessel of the EUV radiation source,
• wherein the vessel comprises a collector mirror,
• wherein an angle between an optical axis of the second reflected laser beam and a horizontal axis is smaller than 25 degrees,
• wherein the horizontal axis is defined by the optical axis of the collector mirror,
• wherein the laser beam is received by one or more additional mirrors that redirect the laser beam towards the first curved mirror;
• and wherein the one or more additional mirrors are configured to overcome a difference in location between the received laser beam and the redirected laser beam, and to translate the laser beam in a substantially vertical direction.