Parshani Idan, Bello Leon, Meller Mallachi-Elia, Pe'er Avi
Department of Physics and BINA Institute of Nanotechnology, Bar-Ilan University, Ramat-Gan, 52900, Israel.
Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ, USA.
Sci Rep. 2022 Sep 1;12(1):14874. doi: 10.1038/s41598-022-19098-4.
Dissipative solitons are fundamental wave-pulses that preserve their form in the presence of periodic loss and gain. The canonical realization of dissipative solitons is Kerr-lens mode locking in lasers, which delicately balance nonlinear and linear propagation in both time and space to generate ultrashort optical pulses. This linear-nonlinear balance dictates a unique pulse energy, which cannot be increased (say by elevated pumping), indicating that excess energy is expected to be radiated in the form of dispersive or diffractive waves. Here we show that Kerr-lens mode-locked lasers can overcome this expectation. Specifically, by breaking the spatial symmetry between the forward and backward halves of the round-trip in a linear cavity, the laser can modify the soliton in space to incorporate the excess energy. Increasing the pump power leads therefore to a different soliton solution, rather than to dispersive/diffractive loss. We predict this symmetry breaking by a complete numerical simulation of the spatio-temporal dynamics in the cavity, and confirm it experimentally in a Kerr-lens mode-locked Ti:Sapphire laser with quantitative agreement to the simulation. The simulation opens a window to directly observe the nonlinear space-time dynamics that molds the soliton pulse, and possibly to optimize it.
耗散孤子是在存在周期性损耗和增益的情况下仍能保持其形态的基本波脉冲。耗散孤子的典型实例是激光中的克尔透镜锁模，它在时间和空间上巧妙地平衡非线性和线性传播，以产生超短光脉冲。这种线性 - 非线性平衡决定了一个独特的脉冲能量，该能量无法增加（例如通过提高泵浦功率），这表明多余的能量预计会以色散波或衍射波的形式辐射出去。在此我们表明，克尔透镜锁模激光器可以克服这一预期。具体而言，通过打破线性腔往返过程中前向和后向两半部分之间的空间对称性，激光器可以在空间上对孤子进行修改，以纳入多余的能量。因此，增加泵浦功率会导致不同的孤子解，而不是色散/衍射损耗。我们通过对腔内时空动力学进行完整的数值模拟预测了这种对称性破缺，并在一台克尔透镜锁模钛宝石激光器中通过实验证实了这一点，实验结果与模拟结果在定量上吻合。该模拟为直接观察塑造孤子脉冲的非线性时空动力学打开了一扇窗口，并且可能有助于对其进行优化。
