Simulation of picosecond pulse propagation in fibre-based radiation shaping units

Stretching of picosecond laser pulses with uniform reflecting volume Bragg gratings

“…The η theor value indicating the pulse reflection efficiency, 10.6% is relatively small for the parameters of our experiment, as a result, the shape of the I A (l,t) profile calculated at the opposite side of the VBG should be similar to that of the I A (0, t) profile, with an additional shift due to the time delay T VBG = n 0 l/c = 38.5 ps of the propagation inside the grating. The results of the calculations performed using equations (12)- (14), which are presented in figure 2, confirm these conclusions regarding the shape of the transmitted pulse. The I A (0, t) profile was obtained with the maximum initial value equal to unity, using equations (10) and (14), and both the I A (0, t) and I A (l, t) profiles are presented in figure 2.…”

“…The results of the calculations performed using equations (12)- (14), which are presented in figure 2, confirm these conclusions regarding the shape of the transmitted pulse. The I A (0, t) profile was obtained with the maximum initial value equal to unity, using equations (10) and (14), and both the I A (0, t) and I A (l, t) profiles are presented in figure 2. A reduction factor of 50 was applied to these data in order to facilitate comparison between these profiles and that of I B (0, t).…”

“…The narrow Gaussian fit of the autocorrelation measurements for the incident pulse shown in figure 3 yields an FWHM peak width equal to 13.2 ps. This value is √ 2 times smaller than the FWHM pulse duration T p = 9.3 ps of I A (0,t), according to equations ( 10), (14), and ( 16):…”

“…In addition, application of this technique with high-power pulses is limited by the low damage threshold of the surface gratings and by difficulties regarding the stretching of pulses with initial durations of a few picoseconds or longer. The development of laser systems with variable pulse duration in picosecond range continues mostly with the utilization of surface diffraction gratings [13,14]. A simple method to control the duration of short laser pulses can be also implemented based on apparatus containing a dispersive element and focusing optics [15].…”