Magnetically controllable slow light based on magnetostrictive forces.

The magnetostrictive effect provides an opportunity for exploring fundamental phenomena related to the phonon-magnon interaction. Here we show a tunable slow light in a cavity magnetomechanical system consisting of photon, magnon and phonon modes with a nonlinear phonon-magnon interaction, which originates from magnetostrictive forces. For a strong photon-magnon coupling strength, we can observe a transparency (absorption) window for the probe by placing a strong control field on the red (blue) detuned sideband of the hybridized modes, which are comprised of photons and magnons. In this work, we mainly show the characteristic changes in dispersion in the range of the transparency window. The value of group delay can be continuously adjusted by using different frequencies of magnon, which are determined by the external bias magnetic field and therefore can be conveniently tuned in a broad range. Both the intensity and the frequency of the control field have an influence on the transformation from subluminal to superluminal propagation and vice versa. Furthermore, one may achieve long-lived slow light (group delay of millisecond order) by enlarging the pump power. These results may find applications in information interconversion based on coherent coupling among photons, phonons and magnons.