Deeply subwavelength phonon-polaritonic crystal made of a van der Waals material
Deeply subwavelength phonon-polaritonic crystal made of a van der Waals material
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DOI：
10.1038/s41467-018-07795-6
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发表时间：
2019-01-03
影响因子：
16.6
通讯作者：
Nikitin, A. Y.
中科院分区：
文献类型：
--
作者：
Alfaro-Mozaz, F. J.;Rodrigo, S. G.;Nikitin, A. Y.
光子晶体（PC）是周期性图案化的，它提供了整形和减慢光的机会，用于光信号的处理、激光发射和自发发射控制。传统PC的单位单元与光的波长相当，不适合亚波长尺度的应用。我们在货车德瓦尔斯材料（h-BN）中设计了一个纳米级孔阵列，支持超限制声子极化激元（PhPs）-耦合到电磁场的原子晶格振动。这样的孔阵列表示用于中红外频率的极化激元晶体，其具有10（-5）λ（3）（0）的晶胞体积（λ（0）是自由空间波长），其中PhP形成具有非常平坦的色散带的超受限布洛赫模式。后者导致角度和偏振无关的尖锐布拉格共振，验证了远场光谱和近场光学显微镜。我们的研究结果可能会导致新的小型化的角度和偏振无关的红外窄带耦合器，吸收器和热发射器的基础上货车德瓦尔斯材料和其他薄极性材料。
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 10(-5)lambda(3)(0) (with lambda(0) 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.