Resonant optical nonlinearities and related many-body effects

Bo Fang, Lei Xu, Jie Wang +2 more

In this paper, we reviewed the theoretical and experimental studies on the manipulation of the group delay of light based on the transverse phase modulation effect induced by a Gaussian beam. We introduced the basic theory of slow and fast lights in a thin nonlinear material based on the transverse phase modulation effect. We introduced a simple but effective technique to actively and chromatically control the group velocity of light at arbitrary wavelength, therefore, eliminating the requirements on the optical nonlinearity and the photonic resonance at the signal wavelength. Furthermore, a technique to improve the transverse-modulation-induced relative delay of light in nonlinear media through the combination of an optical nonlinearity and a resonant Fabry-Perot cavity was introduced and theoretically demonstrated in ruby as an example. The introduction of a resonant Fabry-Perot cavity can improve the relative delay by orders of magnitude. The techniques of active chromatic manipulation and resonant improvement of the group delay of light may have potential applications in optical information processing and optical communication network.

Tao Wang, An Li, Zheyuan Tan

Exciton saturation and optical nonlinearities in multiple quantum wells due to many body interactions consisting of phase-space filling and Coulomb screening are investigated. We have made a theoretical model to compare the different effects induced by the two many-body interactions. We focus our calculations on the shift of the exciton absorption resonance at highly excited carrier densities in MQW which can be obtained through femtosecond pump-probe technique. We find that the blue shift of the exciton absorption resonance wavelength caused by the phase-space filling effects is about equivalent to the red shift of Coulomb screening effects in same circular polarization, while in contrary the red shift is much lager than the blue shift in opposite circular polarization. This phenomenon happens within optical switching timescale.

Valerii S. Butylkin, Yury G. Khronopulo, A. E. Kaplan +1 more

H. Haug

The optical spectra of laser-excited semiconductors change with varying laser intensity. Close to exciton or biexciton resonances these optical nonlinearities are, e.g., large enough to obtain optical bistability. The cause for these large nonlinearities are many-body effects in the system of the electron-hole pair excitation. The use of nonequilibrium Green’s functions, or if a quasi-equilibrium exists of thermal Green’s functions, makes it possible to take radiative and Coulomb interactions consistently into account.