A proposal for spectral broadening of an intense laser pulse with energy 15 mJ and a pulse duration of 40 fs in an argon-filled hollow fiber, using conjugate pressure-gradient method, is presented. The design, to be referred as conjugate pressure-gradient method, shall consist of a pair of hollow-fiber segments, each with gas pressure that increasingly and decreasingly varies, respectively. It is expected that the occurrence of early self-focusing can be avoided, as well as the elimination of the additional nonlinear processes at hollow fiber exit. Simulation using 15 mJ, 40 fs laser pulses shows that, in the intensity regime where ionization is important, excellent spectral broadening and spectral phase of the pulses can be obtained using the proposed conjugate pressure gradient method. The method therefore shall be useful for the spectral broadening of high-energy, ultrashort laser pulses.
© 2005 Optical Society of AmericaPDF Article