An Efficient Collinear FROG System to Character the Ultrafast Infrared Laser Pulse

We realized one efficient collinear FROG system to measure the infrared ultrafast laser pulse. The procedure, based on the type-II nonlinear crystal, allows measuring the SHG- FROG trace efficiency. The experimental regime has many advantages. For example, it is intrinsically simple that provides two ports for the input pulse laser in fiber or space. And, the system is of high sensitivity (3.5 pJ@ll MHz) that allows measuring some weak laser pulses. In addition, we proposed a multiple bin algorithm in phase retrieval, based on the constrained nonlinear multi-variable optimization, to reconstruct the FROG trace. The proposed collinear FROG provides good versatility as well as the ability to character the ultrafast laser pulse.