Higher harmonic generation driven by E(t) from the Kerr index of refraction for the optical, NIR, and MIR femtosecond light pulses for the attosecond and zeptosecond pulse generation (Keynote Presentation)

This presentation enhances the understanding of the underlying mechanism behind the generation of higher harmonics from electronic self-phase modulation which is driven by the Electric Field E(t) of the optical, NIR, and MIR femtosecond light pulses to produce attosecond laser pulses and providing the direction to produce zeptosecond laser pulses. The HHG arises from driving the phase of the electric field, E(t) by itself to create HHG in form of odd Bessel functions in time of odd harmonics driven by laser pulse from the nonlinear refractive index of Kerr media, n2 (χ3) and extending to even HHG from n1 (χ2).The three characteristic features of HHG spectrum are initial decreasing harmonics, a plateau region of HHG, and cutoff frequency. We show theoretically in the EM Kerr electronic self-phase modulation (ESPM) model that the distinctive features of HHG arise mainly from the changes in the phase of the E(t) wave driven by the envelope of the laser pulse causing the cosine of the cosine squared for χ3 and the cosine of the cosine for χ2 in time. The outcomes are Bessel function expansions producing odd harmonics for n2 (χ3) and even harmonics for n1 (χ2).