In this work we report a new method for controlling the bandwidth of few-cycle optical pulses, using another femtosecond laser pulses chirped in a neonfilled hollow-core fibre. The observed bandwidth varies from 25 to 234 nm in the optical wavelength region 600–950 nm. The pulse energy has for the first time reached a sub-millijoule frontier at 1 kHz. The input pulses are positively chirped using a chirped-pulse amplifier to acquire the widths 32–56 fs at the entrance of the hollow fibre. Then the pulses are highly dispersed due to a self-phase modulation in a nonlinear medium (a neon gas) followed by a pair of chirped mirrors that compensate the dispersion. We have found that this scheme allows for direct tuning of the output-pulse bandwidth while varying the chirping of the input pulses under different neon-gas pressures. Our results can give an opportunity for controlling the interactions in strong electric fields on the ultrafast time scales and are crucial for regenerating attosecond X-ray pulses.
ا.د. وليد توفيق يونس | Prof. Walid Tawfik | 6375