Zhou Kun, Cheng Qiang, Song Jinlin, Lu Lu, Jia Zhihao, Li Junwei
Appl Opt. 2018 Jan 1;57(1):102-111. doi: 10.1364/AO.57.000102.
We numerically investigate the broadband perfect infrared absorption by tuning epsilon-near-zero (ENZ) and epsilon-near-pole (ENP) resonances of multilayer indium tin oxide nanowires (ITO NWs). The monolayer ITO NWs array shows intensive absorption at ENZ and ENP wavelengths for p polarization, while only at the ENP wavelength for s polarization. Moreover, the ENP resonances are almost omnidirectional and the ENZ resonances are angularly dependent. Therefore, the absorption bandwidth is broader for p polarization than that for s polarization when polarized waves are incident obliquely. The ENZ resonances can be tuned by altering the doping concentration and volume filling factor of ITO NWs. However, the ENP resonances only can be tuned by changing the doping concentration of ITO NWs, and volume filling factor impacts little on the ENP resonances. Based on the strong absorption properties of each layer at their own ENP and ENZ resonances, the tuned absorption of the bilayer ITO NWs with the different doping concentrations can be broader and stronger. Furthermore, multilayer ITO NWs can achieve broadband perfect absorption by controlling the doping concentration, volume filling factor, and length of the NWs in each layer. This study has the potential to apply to applications requiring efficient absorption and energy conversion.
我们通过调节多层铟锡氧化物纳米线（ITO NWs）的近零介电常数（ENZ）和近极点介电常数（ENP）共振，对宽带完美红外吸收进行了数值研究。单层ITO NWs阵列对于p偏振在ENZ和ENP波长处表现出强烈吸收，而对于s偏振仅在ENP波长处有吸收。此外，ENP共振几乎是全向的，而ENZ共振与角度有关。因此，当偏振波斜入射时，p偏振的吸收带宽比s偏振的更宽。ENZ共振可以通过改变ITO NWs的掺杂浓度和体积填充因子来调节。然而，ENP共振只能通过改变ITO NWs的掺杂浓度来调节，体积填充因子对ENP共振影响很小。基于每层在其自身的ENP和ENZ共振处的强吸收特性，具有不同掺杂浓度的双层ITO NWs的可调吸收可以更宽且更强。此外，多层ITO NWs可以通过控制每层NWs的掺杂浓度、体积填充因子和长度来实现宽带完美吸收。这项研究有潜力应用于需要高效吸收和能量转换的应用中。
