Analysis of the steady-state photorefractive harmonic gratings

The steady-state exact solution for the higher harmonic gratings that synth esize the space-charge field are derived without restrictions within the Ku khtarev model. This allows us to know exactly the behavior of the harmonic amplitudes in terms of main parameters and the space-charge field spatial d istribution. The amplitudes of the several gratings were found not to depen d on the mean intensity of the fringe pattern in a typical cw range. With r espect to the modulation depth m, the dependence of each v-order harmonic a mplitude is rigorously established as m(v). Also, regions of quite differen t behavior in terms of the grating spacing are identified and analyzed. Fro m this analysis, it is emphasized that the higher gratings tend to appear m ore strongly for materials with smallest ratio of donors traps, and for inc reasing values of both modulation depth, and spacing grating. Also, the hig her gratings behavior in terms of applied field is analyzed. The relative i mportance of high harmonics is more evident for smallest values of the exte rnal field. [S0163-1829(99)06915-5].