Damage of KDP crystals by ultrashort laser pulses

An investigation was made of the action of ultrashort laser pulses on linear KDP crystals. The damage was found to be discrete and independent of the orientation of the crystals or the focal length of the lenses employed. The threshold damage energy increased with the focal length of the lenses. This energy decreased severalfold when λ₁ = 1.06 μ. radiation was replaced with λ₂ = 0.53 μ pulses. Two-frame pulse holography was used to demonstrate that the damage spread in both directions from the focal plane. The velocity of the damage front in the direction toward the laser was found to be 1.6 × 10¹⁰ cm/sec.