Passive anti-return device for high power ruby laser

High-power ruby lasers with an amplifier chain must be protected from light returns toward the oscillator. We show that it is possible to use a process combining a saturable absorber and a prism polarizer followed by a delay plate. We observed the transmission curves of RG715 type saturable glasses versus illumination and time. The transmission factors derived are compared to measures done with an 80 MW ruby laser. With anti-reflection coatings on the optical elements, the transmission factor of the direct laser wave is 75 per cent whereas the extinction ratio of the return wave is 0.00002.