Air breakdown in coupling area of high peak power laser pulse and silica optical fiber

The air breakdown in the coupling area of 15 MW laser pulse and 600 μm silica optical fiber is investigated. The air breakdown of the focal area is theoretically and experimentally researched. The air breakdown threshold is measured as 0.79×109 W/cm2。. The laser induced damage threshold of the solid medium is measured as 2.12×109 W/cm2。, which is consistent with the theory analyze. A sevenfiber coupler is presented to solve the air breakdown problem. The coupling efficiency of the seven fiber bundle tested is 67.21%. It is concluded that the sevenfiber coupler could couple 15 MW laser pulse into 600 μm silica optical fiber．