Su Xinzhou, Zou Kaiheng, Zhou Huibin, Song Hao, Wang Yingning, Zeng Ruoyu, Jiang Zile, Duan Yuxiang, Karpov Maxim, Kippenberg Tobias J, Tur Moshe, Christodoulides Demetrios N, Willner Alan E
Opt Express. 2024 Jul 15;32(15):26653-26666. doi: 10.1364/OE.527713.
In general, space-time wave packets with correlations between transverse spatial fields and temporal frequency spectra can lead to unique spatiotemporal dynamics, thus enabling control of the instantaneous light properties. However, spatiotemporal dynamics generated in previous approaches manifest themselves at a given propagation distance yet are not arbitrarily tailored longitudinally. Here, we propose and demonstrate a new versatile class of judiciously synthesized wave packets whose spatiotemporal evolution can be arbitrarily engineered to take place at various predesigned distances along the longitudinal propagation path. Spatiotemporal synthesis is achieved by introducing a 2-dimensional spectrum comprising both temporal and longitudinal wavenumbers associated with specific transverse Bessel-Gaussian fields. The resulting spectra are then employed to produce wave packets evolving in both time and axial distance - in full accord with the theoretical analysis. In this respect, various light degrees of freedom can be independently manipulated, such as intensity, polarization, and transverse spatial distribution (e.g., orbital angular momentum). Through a temporal-longitudinal frequency comb spectrum, we simulate the synthesis of the aforementioned wave packet properties, indicating a decrease in relative error compared to the desired phenomena as more spectral components are incorporated. Additionally, we experimentally demonstrate tailorable spatiotemporal fields carrying time- and longitudinal-varying orbital angular momentum, such that the local topological charge evolves every ∼1 ps in the time domain and 10 cm axially. We believe our space-time wave packets can significantly expand the exploration of spatiotemporal dynamics in the longitudinal dimension. Such wave packets might potentially enable novel applications in light-matter interactions and nonlinear optics.
一般来说，横向空间场与时间频谱之间具有相关性的时空波包能够导致独特的时空动力学，从而实现对瞬时光特性的控制。然而，先前方法中产生的时空动力学在给定的传播距离处表现出来，但在纵向不能进行任意调整。在此，我们提出并展示了一类新的通用的经过精心合成的波包，其时空演化可以被任意设计，使其在沿着纵向传播路径的各种预先设计的距离处发生。时空合成是通过引入一个二维频谱来实现的，该频谱包含与特定横向贝塞尔 - 高斯场相关的时间和纵向波数。然后利用所得频谱来产生在时间和轴向距离上都演化的波包——这与理论分析完全一致。在这方面，可以独立操纵各种光自由度，例如强度、偏振和横向空间分布（例如，轨道角动量）。通过时间 - 纵向频率梳频谱，我们模拟了上述波包特性的合成，结果表明，随着纳入更多频谱分量，与期望现象相比相对误差减小。此外，我们通过实验证明了携带随时间和纵向变化的轨道角动量的可定制时空场，使得局部拓扑电荷在时域中每约1皮秒变化一次，在轴向上每10厘米变化一次。我们相信我们的时空波包能够显著扩展在纵向维度上对时空动力学的探索。这样的波包可能会在光与物质相互作用和非线性光学中实现新的应用。
