When the laser intensity exceeds $10^18$W/㎠, an intensity well within the reach of the present laser technology, the energy of the electron driven by the laser becomes comparable to or exceeds the rest mass energy of the electron. An accurate description of the behavior of the electrons driven by such strong lasers thus requires relativistic treatment. In this thesis relativistic effects on high harmonic generation by electrons driven by an intense laser field are investigated through computation of angular and spectral distributions of the radiation emitted by the electrons.
