Anisotropic mirrors are used to form a laser resonator exhibiting non-hermitian, parity-time (PT) symmetric, polarization states. The relative angle of the two mirrors’ principal axes is used to control the degree of non-hermiticity. A sharp symmetry-breaking transition is observed at a specific angle, called the exceptional point, where the two states coalesce into a single polarization state and the interference pattern produced by counter-propagating (CP) waves vanishes. At a smaller angle, in the unbroken PT symmetry regime, the polarization state experiencing higher losses is suppressed. In the broken symmetry regime, the two polarization states coexist, but the orthogonality of the CP waves promotes single longitudinal mode emission by suppressing the interference pattern of the standing wave. The two regimes meet at the exceptional point, where a unique polarization state exists in a resonator free from axial intensity modulation. Microchip PT-symmetric lasers operating at the exceptional point are thus an attractive solution to achieve single mode operation from a miniature monolithic device without any intra-cavity element.

中文翻译：

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使用奇偶时间对称偏振本征态的单模激光器

各向异性反射镜用于形成激光谐振器，该谐振器表现出非埃尔米特，奇偶时间（PT）对称的偏振态。两个反射镜主轴的相对角度用于控制非辐射度。在一个称为异常点的特定角度观察到了一个尖锐的对称破坏跃迁，在该异常点处，两个状态合并为一个极化状态，并且由反向传播（CP）波产生的干涉图消失了。在较小的角度下，在不间断的PT对称状态下，受到较高损耗的偏振态受到抑制。在破坏对称状态下，两个极化状态共存，但是CP波的正交性通过抑制驻波的干涉图样而促进了单纵模发射。两种政权在一个特殊的时刻相遇，谐振器中存在唯一的极化状态，没有轴向强度调制。因此，工作在最佳点的Microchip PT对称激光器是一种吸引人的解决方案，可通过无腔内元件的微型单片器件实现单模工作。