Vol. 11, issue 02-03, article # 27

Abstract:

We present here an equation derived in the geometric optics approximation that describes the evolution of ultrashort pulses in an absorbing medium. This is the Burgers-Korteweg-de Vries (BKV) equation where the amplitude of the Poynting vector is taken as the unknown function. We have numerically simulated the evolution of picosecond pulses in a quartz optical wave guide where no absorption is present (the Korteweg-de Vries equation). During their evolution picosecond pulses are decomposed into femtosecond solitons (≈ 200 fs). Duration of the solitons is inversely proportional to the soliton amplitude to the power of 1/2. In the case when no dispersion is present the width of the arising shock wave is proportional to the absorption coefficient and to the electromagnetic wave period, and inversely proportional to the radiation intensity. At the intensity of 100-1000 W/cm2, the width of the shock wave front equals 100-1000 periods of the electromagnetic radiation wave.