Ultraslow Gaussian pulse propagation induced by a dispersive phase coupling in photorefractive bismuth silicon oxide crystals at room temperature

By use of the highly dispersive phase coupling effect in a photorefractive wave mixing process, we have observed ultraslow propagation of a single Gaussian light pulse with a group velocity ∼0.5 m/s in a photorefractive Bi₁₂SiO₂₀ crystal at room temperature. The ultraslow Gaussian pulse is amplified due to an intensity coupling effect but keeping its Gaussian profile with high fidelity. The group velocity of the Gaussian pulse can be controlled to a large extent. This technique is useful for controllable optical delay lines.