Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4A, Aalborg Øst DK-9220, Denmark.
Nat Commun. 2012 Jul 24;3:969. doi: 10.1038/ncomms1976.
Excitation of localized and delocalized surface plasmon resonances can be used for turning excellent reflectors of visible light, such as gold and silver, into efficient absorbers, whose wavelength, polarization or angular bandwidths are however necessarily limited owing to the resonant nature of surface plasmon excitations involved. Nonresonant absorption has so far been achieved by using combined nano- and micro-structural surface modifications and with composite materials involving metal nanoparticles embedded in dielectric layers. Here we realize nonresonant light absorption in a well-defined geometry by using ultra-sharp convex metal grooves via adiabatic nanofocusing of gap surface plasmon modes excited by scattering off subwavelength-sized wedges. We demonstrate experimentally that two-dimensional arrays of sharp convex grooves in gold ensure efficient (>87%) broadband (450-850 nm) absorption of unpolarized light, reaching an average level of 96%. Efficient absorption of visible light by nanostructured metal surfaces open new exciting perspectives within plasmonics, especially for thermophotovoltaics.
局部和非局域表面等离激元共振的激发可将金、银等可见光的优良反射体变成高效吸收体，但由于涉及的表面等离激元激发的共振性质，其波长、偏振或角带宽必然受到限制。到目前为止，非共振吸收是通过使用组合的纳米和微结构表面修饰和涉及金属纳米粒子嵌入介电层的复合材料来实现的。在这里，我们通过使用超锐利的凸金属槽通过亚波长楔形散射激发的间隙表面等离激元模式的绝热纳米聚焦来在明确定义的几何形状中实现非共振光吸收。我们通过实验证明，金的二维尖锐凸槽阵列可确保高效（>87％）宽带（450-850nm）吸收非偏振光，达到 96％的平均水平。纳米结构金属表面对可见光的高效吸收为等离子体学开辟了新的令人兴奋的前景，特别是对于热光伏。
