Generation of broadband mid-infrared pulses by noncollinear difference frequency mixing

The generation of broadband mid-infrared (MIR) laser pulses by difference frequency mixing (DFM) is investigated. Two-color femtosecond pulses from a Ti:sapphire laser system are mixed in an AgGaS2 crystal using a noncollinear phase matching scheme. The relative bandwidth of the generated MIR pulse has been measured to be 23% of the central frequency, the broadest in DFM-based MIR sources reported thus far. It is found that a type-I crystal can yield a broader phase matching range of the spectrum than a type-II crystal within this scheme.