Accumulating Nonlinear Optical Effects in a Pump Field with a Broad Frequency Spectrum

Hirokazu Tsunetsugu, Eiichi Hanamura

Several nonlinear optical phenomena are described exactly for two-level electronic systems with a Gaussian frequency modulation under a pump field of arbitrary strength. We discuss the emission spectrum and the absorption spectrum of weak probe field under pumping in the frequency region, and the free induction decay (FID) and the optical nutation (ON) as examples of the coherent optical transients in the time region. It is shown that the relaxation behavior depends upon the pumping field intensity, i.e., the effect of the frequency modulations is reduced when the Rabi frequency increases beyond the amplitude or the inverse correlation time of the frequency modulation. We further show that the relaxation behavior depends upon the particular nonlinear optical phenomena, i.e., the vertex correction due to the frequency modulation works in the FID but does not in the ON.

Jing Huang, Mingxiang Gui

The normalized phase-amplitude representation and the Darboux figure are first defined. Then as an example, we establish the quantum optics description for the field in photonic crystal fibers in the defined representation. The field is evolved from one Darboux state to another state in the Darboux figure. By the continuous inputting (pump) of light, the waves induced by nonlinear effects become stronger (the wave frequency number remains constant at the same distance, and their intensities accumulate). The blueshifted waves induced by the third-order resonant susceptibility are not strong enough to cover other nonlinear effect and turn weak along the length (pump turns weak).

Claude N. Cohen-Tannoudji

Alexander A. Balandin, Supriyo Bandyopadhyay

The magnetic-field dependence of the third-order excitonic nonlinear susceptibility ${\mathrm{\ensuremath{\chi}}}^{(3)}$ in a quantum wire is explored within the rotating wave approximation. Both the real and imaginary parts of ${\mathrm{\ensuremath{\chi}}}^{(3)}$, arising from population saturation of the excitonic state under optical pumping, are calculated for a GaAs wire as a function of magnetic field and pump-probe detuning frequencies. The imaginary part of ${\mathrm{\ensuremath{\chi}}}^{(3)}$ exhibits a negative peak associated with the bleaching of the excitonic resonance and a positive, broad, off-resonance absorption peak associated with biexciton formation. The amplitude, line shape, and spectral frequency of both these peaks can be modulated by a magnetic field which indicates the possibility of using such a field to probe the mechanism underlying optical nonlinearity in a quantum wire. Furthermore, the field can also be used to tune the optical nonlinearity over a range of frequencies which has device applications. \textcopyright{} 1996 The American Physical Society.