Nonlinear multi-pass cavity-based devices for enhancing optical pulse contrast

Abstract

A multi-pass cavity-based optical pulse contrast enhancement device is disclosed which selectively attenuates prepulses and other undesired low-power pulse features. The device may include two or more optical mirrors, an intracavity nonlinear medium, and a spatial filtration arrangement that may be inside or outside of the cavity. The nonlinear medium enables a cavity configuration where low-power pulse features may be cavity-unstable and / or mode-mismatched whereas the high-power region may be cavity-stable and / or mode-matched. Propagation through the cavity distinguishes the low-power and high-power pulse regions in their spatial beam characteristics, enabling low-power suppression via diffraction losses, beam distortion, or spatial filtration. This improves upon prior solutions in that it improves pulse contrast by several orders of magnitude at high main pulse transmission efficiency, preserves near-diffraction limited beam quality, is compatible with high laser average powers and pulse repetition rates, and is configurable to accommodate high, e.g., multi-Joule pulse energies.

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