When a Dammann grating is used to split a beam of femtosecond laser pulses into multiple equal-intensity beams, chromatic dispersion will occur in beams of each order of diffraction and with different scale of angular dispersion because the incident ultrashort pulse contains a broad range of spectral bandwidths. We propose a novel method in which the angular dispersion can be compensated by positioning an m-time-density grating to collimate the mth-order beam that has been split, producing an array of beams that are free of angular dispersion. The increased width of the compensated output pulses and the spectral walk-off effect are discussed. We have verified this approach theoretically and validated it through experiments. It should be highly interesting in practical applications of splitting femtosecond laser pulses for pulse-width measurement, pump-probe measurement, and micromachining at multiple points.
© 2005 Optical Society of America
(050.1380) Diffraction and gratings : Binary optics
(050.2770) Diffraction and gratings : Gratings
(320.7080) Ultrafast optics : Ultrafast devices
(320.7160) Ultrafast optics : Ultrafast technology
Guowei Li, Changhe Zhou, and Enwen Dai, "Splitting of femtosecond laser pulses by using a Dammann grating and compensation gratings," J. Opt. Soc. Am. A 22, 767-772 (2005)