Static-electric-field effects on high harmonic generation

High harmonic generation in the presence of a static electric field is analyzed theoretically by an extension of the zero-range potential model treatment of Becker et al. [Phys. Rev. A 50, 1540 (1994)]. For ${\mathrm{H}}^{-}$ and a C${\mathrm{O}}_2$ laser of 5 × ${10}^{10}$ W/${\mathrm{cm}}^2$ intensity, a static electric field of 100 kV/cm is shown to produce a plateau from the 3rd to the 23rd harmonic in which neighboring even and odd harmonics are of comparable intensity. Furthermore, odd harmonics on the plateau are one or more orders of magnitude more intense than in the absence of the static electric field. Dependence of emission rates on laser intensity and results for harmonic generation by Ar are also presented.