In cutting-edge optical technologies, polarization is a key for encoding and transmitting vast information, highlighting the importance of selectively switching and modulating polarized light. Recently, anisotropic two-dimensional materials have emerged for ultrafast switching of polarization-multiplexed optical signals, but face challenges with low polarization ratios and limited spectral ranges. Here, we apply strain to quasi-one-dimensional layered ZrSe₃ to enhance polarization selectivity and tune operational energies in ultrafast all-optical switching. Initially, transient absorption on unstrained ZrSe₃ reveals a sub-picosecond switching response in polarization along a specific crystal axis, attributed to shifting-recovery dynamics of an anisotropic exciton. However, its polarization selectivity is weakened by a slow non-excitonic response in the perpendicular polarization. To overcome this limitation, we apply strain to ZrSe₃ by bending its flexible substrate. The compressive strain spectrally decouples the excitonic and non-excitonic components, doubling the polarization selectivity of the sub-picosecond switching and tripling it compared to that in the tensile-strained ZrSe₃. It also effectively tunes the switching energy at a shift rate of ~93 meV %^-1. This strain-tunable switching is repeatable, reversible, and robustly maintains the sub-picosecond operation. First-principles calculations reveal that the strain control is enabled by momentum- and band-dependent modulations of the electronic band structure, causing opposite shifts in the excitonic and non-excitonic transitions. Our findings offer a novel approach for high-performance, wavelength-tunable, polarization-selective ultrafast optical switching.

在尖端光学技术中，偏振是编码和传输大量信息的关键，凸显了选择性切换和调制偏振光的重要性。最近，出现了用于偏振复用光信号超快切换的各向异性二维材料，但面临着低偏振比和有限光谱范围的挑战。在这里，我们对准一维层状 ZrSe ₃施加应变，以增强偏振选择性并调整超快全光开关中的操作能量。最初，无应变 ZrSe ₃上的瞬态吸收揭示了沿特定晶轴偏振的亚皮秒切换响应，这归因于各向异性激子的位移恢复动力学。然而，其偏振选择性因垂直偏振中的缓慢非激子响应而减弱。为了克服这一限制，我们通过弯曲 ZrSe ₃的柔性基板对其施加应变。压缩应变在光谱上解耦激子和非激子分量，使亚皮秒切换的偏振选择性加倍，并且与拉伸应变 ZrSe ₃相比增加了三倍。它还以~93 meV % ^-1的转换率有效地调节开关能量。这种应变可调的切换是可重复的、可逆的，并且能够稳定地维持亚皮秒操作。第一性原理计算表明，应变控制是通过电子能带结构的动量和能带相关调制实现的，从而导致激子和非激子跃迁发生相反的变化。 我们的研究结果为高性能、波长可调、偏振选择性超快光开关提供了一种新颖的方法。