Laser wakefield accelerators (LWFA) hold great potential to produce high-quality high-energy electron beams (e beams), and wiggling of these LWFA e beams either in the Conventional period magnetic field structure (undulator radiations), strong focusing laser wakefield (betatron radiation), or intense laser fields (Compton scattering) can emit high-energy x-ray photons. By experimentally generating the high-quality LWFA e beams with a good stability and repeatability, we have recently produced tunable quasi-monochromatic ultrahigh brilliance MeV γ-ray via the self-synchronized all-optical Compton scattering scheme and realized a scheme to enhance betatron radiation by manipulating transverse oscillation of electrons in a deflected wakefield with a tilted shock front. The concurrent generation of high-quality e beams and bright x-rays in a compact LWFA may provide practical applications in ultrafast pump-probe study and x-ray radiology fields.
We have investigated the filamentation and self-compression of femtosecond laser pulses in different optical media such as argon gas and fused silica by employing a model developed in the frequency domain. In the case of fused silica, we investigate the nonlinear propagation of femtosecond laser pulses with central wavelengths of 800 nm and 1550 nm, which correspond to the normal group velocity dispersion (GVD) and anomalous GVD regimes, respectively. We have found that the duration of the laser pulse can be self-compressed into less than 10fs from 50 fs for a 1550 nm laser pulse. However, for an 800 nm laser pulse, the self-compressed pulse can only have a duration of about 26 fs. Nevertheless, in the case of 800 nm, by spectral analysis and control, we can obtain sub-5 fs pulses based on the self-guided filaments of femtosecond laser beams. This method avoids the difficulty of complete spectral phase compensation due to the considerable high-order chromatic dispersion.