CIC nanoGUNE, 20018, Donostia-San Sebastián, Spain.
Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, 50009, Zaragoza, Spain.
Nat Commun. 2019 Jan 3;10(1):42. doi: 10.1038/s41467-018-07795-6.
Photonic crystals (PCs) are periodically patterned dielectrics providing opportunities to shape and slow down the light for processing of optical signals, lasing and spontaneous emission control. Unit cells of conventional PCs are comparable to the wavelength of light and are not suitable for subwavelength scale applications. We engineer a nanoscale hole array in a van der Waals material (h-BN) supporting ultra-confined phonon polaritons (PhPs)-atomic lattice vibrations coupled to electromagnetic fields. Such a hole array represents a polaritonic crystal for mid-infrared frequencies having a unit cell volume of [Formula: see text] (with λ being the free-space wavelength), where PhPs form ultra-confined Bloch modes with a remarkably flat dispersion band. The latter leads to both angle- and polarization-independent sharp Bragg resonances, as verified by far-field spectroscopy and near-field optical microscopy. Our findings could lead to novel miniaturized angle- and polarization-independent infrared narrow-band couplers, absorbers and thermal emitters based on van der Waals materials and other thin polar materials.
光子晶体（PCs）是周期性图案化的电介质，为处理光学信号、激光和自发辐射控制提供了控制和减缓光的机会。传统 PC 的单元晶格与光的波长相当，不适合亚波长尺度的应用。我们在范德华材料（h-BN）中设计了纳米级孔阵列，该材料支持超限制的声子极化激元（PhPs）-与电磁场耦合的原子晶格振动。这种孔阵列代表了具有单元晶格体积 [Formula: see text] 的中红外频率的极化晶体（其中 λ 是自由空间波长），其中 PhPs 形成具有非常平坦的色散带的超限制 Bloch 模式。后者导致角度和偏振无关的尖锐布拉格共振，这已通过远场光谱和近场光学显微镜得到验证。我们的研究结果可能会导致基于范德华材料和其他薄极性材料的新型小型化、角度和偏振无关的红外窄带耦合器、吸收器和热发射器。
