Observation of Ultrabroadband Striped Space-Time Surface Plasmon Polaritons
Observation of Ultrabroadband Striped Space-Time Surface Plasmon Polaritons
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DOI：
10.1021/acsphotonics.2c00296
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发表时间：
2022-02
期刊：
影响因子：
7
通讯作者：
Naoki Ichiji;Hibiki Kikuchi;M. Yessenov;K. Schepler;A. Abouraddy;A. Kubo
中科院分区：
文献类型：
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作者：
Naoki Ichiji;Hibiki Kikuchi;M. Yessenov;K. Schepler;A. Abouraddy;A. Kubo
由于表面等离子激元（SPPs）是具有一个自由横向维的表面波，因此SPPs的单色无衍射空间剖面只有余弦波和艾里波。脉冲SPP波包是传播不变的，并且由于其空间和时间频率之间的紧密频谱关联而定位于平面维度，因此被称为“时空”（ST） SPP。由于ST-SPPs独特的时空光谱结构，这种新型等离子体场构型的最佳发射策略仍然是一个悬而未决的问题。我们在这里提出了实现ST-SPPs的关键一步，报告了超宽带条纹ST-SPPs的观测结果。这些是spp，其中每个波长以相对于传播轴的规定角度传播，以产生无衍射的周期性（条纹）横向空间剖面。我们从一个与金介电界面上的ST- spp耦合的自由空间ST波包开始，并通过在由入射ST波包和激发的表面束缚ST- spp叠加产生的双光子荧光中检测到的轴向跳动来明确识别ST- spp。这些结果强调了与ST-SPPs高效可靠耦合的可行方法，从而代表了实现ST-SPPs在等离子体传感和成像方面的全部潜力的关键的第一步。
Because surface plasmon polaritons (SPPs) are surface waves characterized by one free transverse dimension, the only monochromatic diffraction-free spatial profiles for SPPs are cosine and Airy waves. Pulsed SPP wave packets have been recently formulated that are propagation-invariant and localized in the in-plane dimensions by virtue of a tight spectral association between their spatial and temporal frequencies, which have thus been dubbed `space-time' (ST) SPPs. Because of the spatio-temporal spectral structure unique to ST-SPPs, the optimal launching strategy of such novel plasmonic field configurations remains an open question. We present here a critical step towards realizing ST-SPPs by reporting observations of ultrabroadband striped ST-SPPs. These are SPPs in which each wavelength travels at a prescribed angle with respect to the propagation axis to produce a periodic (striped) transverse spatial profile that is diffraction-free. We start with a free-space ST wave packet that is coupled to a ST-SPP at a gold-dielectric interface, and unambiguously identify the ST-SPP via an axial beating detected in two-photon fluorescence produced by the superposition of incident ST wave packet and the excited surface-bound ST-SPP. These results highlight a viable approach for efficient and reliable coupling to ST-SPPs, and thus represent the first crucial step towards realization of the full potential of ST-SPPs for plasmonic sensing and imaging.