The large dispersive properties of wave mixing in liquid crystal light-valves allow obtaining fast and slow light with tunable group velocities. A slow light interferometer is shown by using this interaction.
We present the nonlinear optical properties of liquid crystal light-valves and wave-mixing experiments from which slow-light effects are obtained. Group velocities as low as fractions of mm/s are achieved, the corresponding group index becoming very large. We show how this property that can be exploited to realize interferometric systems, for instance, an enhanced sensitivity Mach-Zehnder interferometer containing the light-valve as a slowlight medium is shown. Then, we present a common-path polarization interferometer based on the anisotropic character of the slow-light process occurring in the light-valve. Finally, we present a nonlinear optical cavity where a Doppler shift is introduced by the controlled displacement of one of the mirrors. Self-pulsing is obtained in the cavity due to the strongly dispersive response of the light-valve.
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.
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.