Gaussian mode selection with intracavity diffractive optics

We outline a resonator design that allows for the selection of a Gaussian mode by diffractive optical elements. This is made possible by the metamorphosis of a Gaussian beam into a flat-top beam during propagation from one end of the resonator to the other. By placing the gain medium at the flat-top beam end, it is possible to extract high energy in a low-loss cavity. A further feature of this resonator is the ability to select the field properties at either end of the cavity almost independently, thus opening the way to minimize the output divergence while simultaneously maximizing the output energy.