Patent ID: 8853657

Claim:
A deep ultraviolet light source comprising: a regenerative ring resonator comprising: a discharge chamber having electrodes and a gain medium between the electrodes; an optical coupler that is partially reflective so that at least a portion of a light beam impinging on the optical coupler from the discharge chamber is reflected back through the discharge chamber and at least a portion of the light beam impinging on the optical coupler from the discharge chamber is transmitted through the optical coupler; and an attenuation optical system in the path of the light beam within the resonator, the attenuation optical system having a plurality of distinct attenuation states, with each attenuation state defining a distinct attenuation factor applied to the light beam; and a control system connected to the attenuation optical system and configured to select an attenuation state applied to the light beam to thereby adjust an energy of the light beam output from the light source.