We show that fast and slow-light result from non-degenerate two-wave mixing in a liquid crystal light-valve. The large response time of the liquid crystals allows obtaining group velocities as slow as 0.13 mm/s.
Two-wave mixing experiments performed in a liquid crystal light-valve leads to optical amplification in the Raman-Nath regime of diffraction. By exploiting the dispersion properties associated with the two-wave mixing gain, we demonstrate slow and fast light effects, with the output signal pulse either delayed or anticipated with respect to the input light field. Group velocity as slow as a 0.2 mm/s are obtained, and a large tunability of the group delay is achieved thanks to the ability of controlling the liquid crystal nonlinear response through the main experimental parameters. A theoretical model based on the Kerr-like response of the liquid crystal light-valve accounts for the experimental results and allows us to calculate the group delays for the different output orders. We show that the large group delay obtained in the slow light regime can be exploited to enhance the spectral sensitivity of a Mach-Zehnder interferometer and, on the other side, the narrow frequency bandwidth of the two-wave mixing gain can be used to realize an adaptive holographic system that achieves picometer detection.
Slow-light is obtained through nonlinear wave-mixing in a liquid crystal light-valve. A deceleration of light pulses down to group velocities as small as 0.2 mm/s is achieved when two-wave-mixing is performed with a continuous pump and a time modulated signal. A model accounts for the observations in the general framework of nonlinear wave-mixing in thin media. The large group delay provided by the light-valve is exploited to enhance the spectral sensitivity of an interferometer, whereas the narrow frequency bandwidth of the two-wave-mixing gain is used to realize an adaptive holographic system that allows achieving subpicometer detection.
Abstract After a review of the basic concepts of slow and fast light, recent advancements based on nonlinear wave‐mixing processes are described. As a nonlinear medium, the authors focus on a liquid crystal light valve showing that it allows obtaining a large control of the group delay, with a maximum fractional delay of 1, and a deceleration of light pulses down to group velocities as small as 0.2 mm/s. A theoretical model accompanies the observations and accounts for them in the general framework of two‐wave mixing in the light valve. At the end, a high‐sensitivity interferometer is presented as an example of slow light applications.