We analyze experimentally and theoretically the chaotic dynamics generated by a laser diode subjected to phase-conjugate feedback. Phase conjugation is obtained from four-wave mixing in a ${\mathrm{BaTiO}}_3$ photorefractive crystal. We demonstrate that the chaos bandwidth first increases linearly with feedback ratio but then saturates to relatively high values. With a single optical feedback, a chaos bandwidth up to about 18 GHz is achieved, which is about five times as large as the free-running laser diode relaxation oscillation frequency. Numerical simulations confirm our experimental observations and unveil that the finite depth penetration into the crystal is responsible for the observed saturation.

中文翻译：

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具有相位共轭反馈的激光二极管引起的宽带混乱

我们从实验和理论上分析激光二极管受到相位共轭反馈产生的混沌动力学。相位共轭是通过四波混频获得的。${\mathrm{钛酸钡}}_3$光折射晶体。我们证明，混沌带宽首先随反馈比线性增加，然后饱和到相对较高的值。通过单个光反馈，可获得高达约18 GHz的混沌带宽，约为自由运行的激光二极管弛豫振荡频率的五倍。数值模拟证实了我们的实验观察结果，并揭示了进入晶体的有限深度渗透是观察到的饱和的原因。