The characteristics of backward harmonic radiation due to electron oscillationsdriven by a linearly polarized fs laser pulse are analysed considering a single electron model.The spectral distributions of the electron's backward harmonic radiation are investigated in detailfor different parameters of the driver laser pulse,Higher order harmonic radiations are possiblefor a sufficiently intense driving laser pulse.We have shown that for a realistic pulsed photonbeam,the spectrum of the radiation is red shifted as well as broadened because of changes in thelongitudinal velocity of the electrons during the laser pulse.These effects are more pronounced athigher laser intensities giving rise to higher order harmonics that eventually leads to a continuousspectrum.Numerical simulations have further shown that by increasing the laser pulse width thebroadening of the high harmonic radiations can be controlled.
