System and Method for Isolating Gain Elements in a Laser System

摘要

A method and apparatus for protecting the seed laser a laser produced plasma (LPP) extreme ultraviolet (EUV) light system are disclosed. An isolation stage positioned on an optical path diverts light reflected from further components in the LPP EUV light system from reaching the seed laser. The isolation stage comprises two AOMs that are separated by a delay line. The AOMs, when open, direct light onto the optical path and, when closed, direct light away from the optical path. The delay introduced by the delay line is determined so that the opening and the closing of the AOMs can be timed to direct a forward-moving pulse onto the optical path and to divert reflected light at other times. The isolation stage can be positioned between gain elements to prevent amplified reflected light from reaching the seed laser and other potentially harmful effects.

主权项

1. A system comprising:
a laser seed module for producing laser light on an optical path; a first gain element positioned along the optical path; a second gain element positioned along the optical path after the first gain element; and an isolation stage positioned along the optical path between the first gain element and the second gain element, the isolation stage configured to divert light that has been reflected back along the optical path through the second gain element, the isolation stage comprising:
a first acoustic-optical modulator (AOM) configured to transition over a first period of time between a first state in which light is directed along the optical path and a second state in which light is not directed along the optical path;a second AOM configured to transition over a second period of time between a first state in which light is directed along the optical path and a second state in which light is not directed along the optical path, the transition of the second AOM occurring at a time after the transition of the first AOM; anda delay device positioned between the first AOM and the second AOM and configured to delay the transmission of light between the first AOM and the second AOM for a time determined based upon the first and second transition times of the AOMs such that any light reflected back along the optical path that passes through the second AOM will not pass through the first AOM and back to the laser seed module.