Theory of relativistic optical harmonic generation

摘要

We present a theoretical model of optical harmonic generationnexcited by laser beams sufficiently intense that relativistic effectsnare important. This model shows that, under relativistic conditions,nthird-harmonic generation can be excited with comparable efficiency byneither linear or circularly polarized light. This result is to bencontrasted with experience from traditional (nonrelativistic) nonlinearnoptics, where group-theoretical arguments show that third-harmonicnemission cannot occur under circularly polarized excitation. Thesenresults are in good agreement with the observed polarization dependencenof the third-harmonic emission reported recently in an experimentnconducted under conditions such that relativistic effects are important.nOur theoretical model also predicts that all even and odd harmonies ofnthe fundamental laser frequency are emitted in the near-forwardndirection with an intensity that increases with that of the incidentnlaser field