Junchi Chen

Simultaneous measurement of laser-induced shock wave and released particle velocities at Mbar pressure

We show the feasibility of simultaneous measurement of shock velocity and released particle velocity after shock at Mbar pressure. The shock wave is driven by a laser pulse of 1.2 ps duration (full width at half maximum), with the intensity of ∼1014 W/cm2 at 785 nm, irradiating a 500-nm-thick aluminum foil. A chirped laser pulse split from the main pulse is applied to detect the shock breakout process at the rear surface of the target based on frequency domain interferometry. The mean shock velocity determination benefits from the precise synchronization (<100 fs resolution) of the shock pump and probe laser pulse, which is calculated from the time the shock takes to travel the 500-nm-thick aluminum. The released particle velocity determination takes advantage of the chirped pulse frequency domain interferometry. The two measured parameters are self-consistent.

Experimental observation of a ps-laser-induced shock wave

We present femtosecond-time-resolved measurements of a Mbar pressure shock wave release process with a chirped pulse spectral interferometer. The phase shift and reflectivity history reveal that the shock accelerates the rear surface before its ablation.

Investigation of pre-pulse pumping laser for preserving temporal waveform of stimulated Raman scattering

A modified polarized beam combination technique is proposed for preserving the temporal waveforms of stimulated Raman scattering. 1064 nm pre-pulse pumping lasers prior to the main pumping laser with a delay time are generated and injected into a Ba(NO3)(2) Raman medium to excite the crystal firstly. The influences of pre-pulse lasers with various energy levels on the temporal shapes of Raman lasers are investigated, and it is demonstrated that the temporal waveforms of the Raman laser are distorted once the energies of the pre-pulse are below and above the required energy for preserving the temporal shapes of Stokes radiation. It is also discovered that the temporal shape of the 1197 nm Raman laser cannot be perfectly preserved if the energy of the 1064 nm main laser is too low or the relative delay time is too large. Moreover, the optical conversion efficiency and Stokes laser energy obtained under pumping lasers with single and double intensity peaks are compared.

Filamentation with third-harmonic generation of femtosecond laser pulses propagating in air

It is shown experimentally that during the femtosecond laser pulse filamentation in air an intense third-harmonic pulse is generated and the characters of filament are inferred by the distribution of the third-harmonic intensity.