Regenerative ring resonator

A method of modifying a laser beam of an electric discharge gas laser, the method comprising:

• directing a laser beam through an optical coupler of a regenerative ring resonator;
• directing the laser beam that passes through the optical coupler through a discharge chamber and back to the optical coupler such that at least some of the light impinging on the optical coupler from the discharge chamber is reflected back through the discharge chamber and at least some of the light impinging on the optical coupler from the discharge chamber is transmitted through the optical coupler;
• and
• transversely expanding a profile of the laser beam such that the near field laser beam profile uniformly fills each aperture within the laser and such that the regenerative ring resonator remains either conditionally stable or marginally unstable when operating the laser at powers that cause thermal lensing of elements within the regenerative ring resonator.

A regenerative ring resonator in the path of a laser beam, the 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 some of the light impinging on the optical coupler from the discharge chamber is reflected back through the discharge chamber and at least some of the light impinging on the optical coupler from the discharge chamber is transmitted through the optical coupler;
• and
• a beam modification optical system in the path of the laser beam;
• wherein the beam modification optical system is configured to transversely expand a profile of the laser beam such that the near field laser beam profile uniformly fills each aperture within the resonator and such that the regenerative ring resonator remains either conditionally stable or marginally unstable when operating the laser at powers that cause thermal lensing of elements inside of the regenerative ring resonator.