Cross Gain Modulation (XGM) is a well-established nonlinear optical technique for all-optical interactions between a modulated beam and a CW one.  As a result of this interaction, the modulation is copied from the modulated input onto the CW beam. We have developed a new type of interaction between pump and Stokes beams in a Brillouin medium, where both input beams are modulated.  Among the prominent features of this effect, which we call Mutually-Modulated Cross-Gain Modulation (MMXGM), we have demonstrated an extremely small group velocity of 10 m/s and nonlinear modulation phase shifts.

MMXGM is a new all-optical nonlinear technique for controlling the modulated waveform of a light beam using another modulated light beam.  Previous work and new results show that with this method it is possible to carry out important RF-photonic processing tasks, such as group velocity and modulation-phase control, slow pulsed light, sum and difference modulation-frequency generation and modulation frequency filtering.  The SBS fiber medium is ideal for distributive sensing applications with this effect, for example we predict sub-nanostrain sensitivity to be easily achieved with MMXGM-induced slow light.  On the other hand, extending this effect to the gigahertz regime with a semiconductor optical amplifier will open up applications in gigahertz photonic processing.