Novel large mode volume resonator

A resonator in which the dominant mode-shaping effect is diffraction from an undersized aperture is reported. The result is a large mode volume and a near diffraction-limited Gaussian output beam. The alignment sensitivity is similar to that of a positive branch unstable resonator, although the mirror configuration can vary over a large range in either the geometrically stable or unstable regimes. A pulsed Nd:YAG laser using this resonator was built and characterized in the free-running, Q-switching, and mode-locking regimes, and as a regenerative amplifier.<
>