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Dispersion of Femtosecond Laser Pulses in a Multipass Gas Cell
Mona Ali and Tarek Mohamed
We present the results of a simulation of the dispersion of femtosecond laser pulses in a multipass cell containing methane gas at atmospheric pressure. The multipass cell with a base length of 1 m has highly reflecting mirrors in a confocal arrangement to achieve long optical paths of 600 m. The femtosecond laser pulse is produced by different femtosecond fiber lasers with a broadband spectral range to study the dispersion at 1.64 μm and 3.3 μm. At 1.64 μm and after 600 reflections, the femtosecond laser pulse was temporally broadened, and the laser pulse duration changed from 108 fs to 326 fs. Strong dispersion was observed at 3.3 μm, and the laser pulse duration increased to 279 ps. To compensate for this broadening, dispersive mirrors with suitable parameters are being proposed.
Keywords: Multipass gas cell, absorption laser spectroscopy, femtosecond laser, group velocity dispersion, self-phase modulation