Generation of double femtosecond pulses by using two transmissive gratings

Double femtosecond laser pulses are usually generated by using a Michelson structure. We propose a novel and simple device by using two high-density transmissive gratings for generation of double pulses and conversion between single and double laser pulses by shifting one of the two gratings by a quarter period. The apparatus has the advantages of compact volume, simple structure, and convenience in manipulation. Experimental outputs of the double laser pulses are well verified in experiment, which can be properly explained by numerical simulation with the rigorous coupled-wave theory. This structure provides an interesting approach for generation of double pulses and conversion between single and double laser pulses for practical applications of the femtosecond laser.