Energetic few-cycle pulse compression in gas-filled hollow core fiber with concentric phase mask
Zhao Yu1, 2, Huang Zhi-Yuan1, 2, Zhao Rui-Rui1, 2, Wang Ding1, †, Leng Yu-Xin1, ‡
       

Schematic diagram of concentric phase mask, where Region 1 represents birefringent half-wave plate.