Research data supporting "Raman-probing the local ultrastrong coupling of vibrational plasmon-polaritons on metallic gratings"

Datasets required to plot figures in main manuscript in Physical Review Letters.

Figure 1. Strong coupling in open gratings. (a) Raman microscopy (pump 532 nm) of grating (period \Lambda=4.7 µm, slot width 1 µm, height h=0.1 µm, with 1 µm thick PMMA layer). (b) Grating IR reflectance spectra in experiment (expt, left) and theory (RCWA, right). (c) Raman scattering from ground state \left.\left|g\right.\right\rangle to excited state \left.\left|e\right.\right\rangle or VibPERS to lower \left.\left|LP\right.\right\rangle and upper \left.\left|UP\right.\right\rangle polariton states. (d) VibPERS spectra of slot and mesa in grating compared to flat regions. Left: Optical image of grating. Middle: Background-corrected Raman spectra. Right: Raman spectra of slot and mesa after subtracting flat spectrum.

Figure 2. Lower polariton enhanced Raman and localization in grating slots. (a) Raman maps acquired at two different heights above the grating surface. (b) Raman map at PMMA surface (z=1 µm) showing integrated peak area of lower polariton (A_{LP}). (c,d) Raman maps at grating surface (z=0 µm) for (c) LP (A_{LP}) and (d) PMMA (A_{PMMA}) modes with shared spectrally-integrated intensity scale. White scale bars are 2µm. (e-h) Laterally averaged A_{LP} and \omega_{LP}-\omega_0 across the grating for (e,f) z=1 µm and (g,h) z=0 µm.

Figure 3. Detuning of grating modes. (a) VibPERS spectra of lower polariton mode for different grating periods (\Lambda). (b) Laterally-averaged lower polariton mode (integrated area) vs x-position, which is localised at the grating slots (vertical bar is 100 cts\cdotcm-1mW-1s-1). Horizontal gray bars indicate slot positions.

Figure 4. Polariton-enhanced Raman scattering in gratings. (a) Field distribution (E_x/E_0) for the lower polariton under near-normal incidence (\theta=0.1°) transverse-magnetic (TM) excitation perpendicular to the grating grooves (dashed). Gold’s permittivity from Ref.25. (b) Coupled oscillator fit to RCWA simulations of grating scattering for upper and lower polariton modes vs momentum (k_x). Colours show vibrational Hopfield coefficient fraction (SI Section S2). (c) Molecular density-of-states (corrected and angle-averaged) showing asymmetric broadening of LP peak (grey bar indicating extinction of 0.1). (d) Polariton states showing scattering from ground state to bright (strongly coupled) and dark states, labelling Raman scattering (\omega) and infrared absorption (\nu). (e) Plasmon-vibration coupling strength g vs normalised position x/\Lambda, with red points from Fig. 2. (f) Map of spatial plasmon-vibration coupling strength g along the \Lambda=4.7 µm grating (modelled surface profile in white).

物理评论快报主论文中绘制图表所需的数据集。

图1. 开放光栅中的强耦合。
(a) 光栅的拉曼显微镜成像（泵浦光波长为532 nm，周期(Lambda=4.7 mu m)，槽宽1 mu m，高度(h=0.1 mu m)，覆盖1 mu m厚的PMMA层）。
(b) 实验中光栅的IR反射光谱（左侧）与理论（RCWA，右侧）。
(c) 从基态(left.left|g
ight.
ight
angle)散射到激发态(left.left|e
ight.
ight
angle)或VibPERS到较低的(left.left|LP
ight.
ight
angle)和较高的(left.left|UP
ight.
ight
angle)极化激元状态。
(d) 与平面区域相比，光栅槽和台地的VibPERS光谱。左侧：光栅的光学图像。中间：背景校正后的拉曼光谱。右侧：减去平面光谱后的槽和台地的拉曼光谱。

图2. 光栅槽中极化激元增强的拉曼散射和局域化。
(a) 在两个不同的高度上获取的拉曼图。
(b) 在PMMA表面（(z=1 mu m)）的拉曼图，显示极化激元（(A_{LP})）的积分峰面积。
(c,d) 光栅表面（(z=0 mu m)）的拉曼图，用于(c) LP（(A_{LP})）和(d) PMMA（(A_{PMMA})）模式，具有共享的光谱积分强度比例。白色刻度尺为2 mu m。
(e-h) 横向平均的(A_{LP})和(omega_{LP}-omega_0)穿过光栅，对于(e,f) (z=1 mu m)和(g,h) (z=0 mu m)。

图3. 光栅模式的失谐。
(a) 不同光栅周期((Lambda))的极化激元模式的VibPERS光谱。
(b) 横向平均的极化激元模式（积分面积）与x位置的关系，该位置位于光栅槽中（垂直条是100 ctscdotcm(^{-1})mW(^{-1})s(^{-1})）。水平灰色条表示槽的位置。

图4. 光栅中的极化激元增强拉曼散射。
(a) 在近垂直入射（( heta=0.1°)）横向磁（TM）激发垂直于光栅刻纹的情况下，下极化激元的场分布（(E_x/E_0)）（虚线）。金介电常数来自参考文献25。
(b) 对上极化激元和下极化激元模式与动量（(k_x)）的RCWA模拟光栅散射进行耦合振荡器拟合。
颜色显示振动Hopfield系数分数（见附录S2）。
(c) 分子态密度（校正并角度平均）显示LP峰的对称性展宽（灰色条表示0.1的消光）。
(d) 极化激元状态显示从基态散射到明（强耦合）和暗状态的拉曼散射（(omega)）和红外吸收（(
u)）。
(e) 表面等离子体振动耦合强度(g)与归一化位置(x/Lambda)的关系，红色点来自图2。
(f) (Lambda=4.7 mu m)光栅沿空间方向上的表面等离子体振动耦合强度(g)的映射（白色表示模拟的表面轮廓）。