Slow and Fast Lights in Photorefractive Materials

Bo Fang, Ze Liu, Feng Gao +2 more

We show theoretically that, based on the dispersive phase coupling effect during the wave mixing process, both slow and fast light can be achieved in GaAs–AlGaAs photorefractive multiple quantum wells (PRMQWs) films applied with a transverse direct-current electric field. The general formula for the group velocity of the diffracted beams in the Raman–Nath regime during the wave mixing process in a nonlinear thin film is derived and is then applied to the case of the PRMQWs films in the transverse geometry. The simulation results in the transverse-geometry PRMQWs films show that the group velocity and bandwidth of slow light can be on the order of centimeter per second and 100 kHz, respectively. The extremely low group velocity and the relatively broad bandwidth are mainly originated from the strong quadratic electro-optic effect and the fast response rate of the PRMQWs films, respectively. Our results show that the delay-bandwidth product of slow light can be significantly improved in PRMQWs films as compared to the reported results in other photorefractive materials.

Wies aw Kr�likowski

Partha Pratim Banerjee, Georges T. Nehmetallah, Rola Aylo +1 more

In this work we theoretically model continuous and pulse wave propagation using the underlying dispersion relations. We also derive the dispersion relations of the underlying wave equations based on the real and imaginary parts of the propagation constant which are related through Hilbert transformation to ensure causality. Also, in this paper we show that by using a model of photorefractive two wave coupling, we can derive the dispersion relation for pulsed propagation and coupling in a diffusion dominated photorefractive material. We note that the dispersion relation we have found in photorefractive material also obeys the Hilbert transform property. Finally, we show that the group velocity of light can be slowed down by means of phase coupling in the photorefractive two-wave mixing process.

Wolfgang Horn, Jan v Bassewitz, Cornelia Denz

We demonstrate slow and fast light by dispersive phase-coupling in a SBN:60 crystal. The gain spectrum is modulated by using multiple frequency shifted pumping beams and the complete dispersion is measured by the phase-modulation technique.

Klaus H. Ringhofer, LASZLO SOLYMAR