F. Agullolopez et Fv. Karpushko, A FIELD-IONIZATION MECHANISM FOR A HIGH REFRACTIVE NONLINEARITY IN HEAVILY-DOPED N-GAAS, Optics communications, 100(1-4), 1993, pp. 181-185
A new microscopic model is proposed to account for the strong and fast
refractive index nonlinearity recently found in heavily doped n-GaAs.
The model involves tunneling ionization of the donors induced by the
space-charge field generated by the nonhomogeneous light intensity pat
tern. In particular, negative refractive index changes DELTAn = -5 x 1
0(3) for excitation pulses of 5 x 10(5) W/cm2 at 885 nm can be reasona
bly explained. Response times are estimated to be in the sub-nanosecon
d regime (10-100 ps).