Drive laser for EUV light source

1. A device comprising:

a laser source producing a continuous output on a beam path;

an amplifier;

a partially transmissive, partially reflective optic disposed on said beam path between said laser source and said amplifier; and

a droplet generator positioned to deliver a droplet moving on a path intersecting said beam path, the droplet reflecting light to establish an optical cavity with said optic.

2. A device as recited in claim 1 wherein said laser source comprises a CO 2 laser having an output in the range of 0.1 W to 100 W.

3. A device as recited in claim 1 wherein said partially transmissive, partially reflective optic reflects between 75% and 99.9% of the laser source output.

4. A device as recited in claim 1 wherein said laser source has a power output, the partially transmissive, partially reflective optic has a reflectivity, and the power output and reflectivity are selected wherein the light entering the amplifier from the oscillator does not substantially deplete gain in the amplifier.

5. A device as recited in claim 1 further comprising an adjustable telescope disposed along said beam path between said oscillator and said amplifier.

6. A device as recited in claim 1 further comprising an optical isolator disposed between said laser source and said partially transmissive, partially reflective optic to protect said oscillator from reflected light.

7. A device as recited in claim 1 wherein the laser source produces a continuous output having at least two lines and the amplifier has a gain band including said two lines.