Harmonic Generation in Focused Laser

Up to now we have considered only harmonic generation by a plane wave. Harmonic generation by a focused laser beam was treated by Kleinman et al (1966), Ward and New (1969) and applied for THG in liquids and in air (environmental effects) by Meredith et al (1983b), Kajzar and Messier 

The resultant harmonic field can be again represented in the complex plane as it is done in Fig. 12 showing harmonic field at the focal point. One can see that the resultant field describes a spiral with radius r=x increasing progressively up to the focal point 

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