Tunable Rotation-Associated Slow-to-Fast Light Conversion via Optomagnonic Coupling

Abstract

Cavity optomechanics has enabled slow-to-fast light conversion, but traditional optomechanic systems suffer from limited tunability due to fixed mechanical frequencies. To address this constraint, we introduce a magnon degree of freedom into an optomechanical system, constructing a system that integrates photons, phonons, and magnons. We establish the theoretical model of the optomagnonic-Laguerre-Gaussian rotational system, and present numerical simulations of Fano resonances and group delay. By manipulating the magnon degree of freedom, we not only achieve slow-to-fast light conversion associated with magnons but also successfully realize such conversion effects associated with mechanical rotation-this achievement effectively overcomes the inherent tunability limitations of pure optomechanical systems and expands the frequency coverage of light conversion effects. Notably, we numerically demonstrate bidirectional light speed conversion (slow-to-fast and fast-to-slow) via continuous control field frequency modulation to tune cavity mode detuning. Additionally, our results show that adjusting optomagnonic parameters enables dynamic switching between slow light and fast light at multiple frequencies. This work provides a flexible platform for multi-frequency light speed control, with potential applications in all-optical networks and quantum communications.

Figures (5)

• Figure 1: Schematic of the optorotational-optomagnonic hybrid model. The incident light is a circularly polarized Gaussian beam: the beam’s orbital angular momentum is transferred to the RM’s rotational angular momentum.
• Figure 2: Comparison of the optorotational system with magnons (red solid line) and without magnons (blue dashed line). Panels (a)–(d) show the influence of magnon introduction on the absorption ($\text{Re}[\varepsilon_{\text{out}}]$), dispersion ($\text{Im}[\varepsilon_{\text{out}}]$), phase ($\phi_t = \arg(t_p)$), and group delay ($\tau_g$) of the probe field, respectively.
• Figure 3: Slow-to-fast light conversion diagrams. Conversion between slow and fast light is achieved by tuning the intensity (a) and frequency (b) of the control field, the magnetic field strength (c), and the optomagnonic coupling (d).
• Figure 4: Slow-to-fast light conversion via continuous parameter tuning. Conversion between slow and fast light is achieved by continuous adjustment of the control field intensity and frequency, the magnetic field strength, and the optomagnonic coupling. The values of the colorbar denote the group delay $\tau_g$ (ms).
• Figure 5: (a) and (b) denote the maximum and minimum group delays associated with the rotational mode; (c) and (d) denote those associated with the magnon mode. For each pair of optomagnonic coupling strength $g_m$ and magnon frequency $\omega_m$, the maximum and minimum group delays ($\tau_g$) presented in the figures are obtained by continuously sweeping the detuning $\delta$ spanning the rotational and magnon frequencies, followed by extracting the extreme values of $\tau_g$ within each respective frequency regime. The values of the colorbar denote the group delay $\tau_g$ (ms).