Reversible Optical Switching of Infrared Antenna Resonances with Ultrathin Phase-Change Layers Using Femtosecond Laser Pulses
Reversible Optical Switching of Infrared Antenna Resonances with Ultrathin Phase-Change Layers Using Femtosecond Laser Pulses
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DOI：
10.1021/ph500121d
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发表时间：
2014-09-01
期刊：
影响因子：
7
通讯作者：
Taubner, Thomas
中科院分区：
文献类型：
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作者：
Michel, Ann-Katrin U.;Zalden, Peter;Taubner, Thomas
近年来，相变材料由于具有可切换的光学性质，在活性超材料和等离子体材料领域引起了人们的极大兴趣。在红外光谱范围内，非晶相和晶相之间的巨大折射率对比度可用于纳米天线或亚表面共振的非挥发性调谐。为了在器件中使用这些概念，必须实现活性材料的可逆切换。在这里，我们通过施加来自钛宝石激光器的飞秒脉冲来演示这种可逆循环。这些光脉冲触发了覆盖在红外纳米天线上的PCM薄膜的相变。选择Ge3Sb2Te6作为相变调制器，是因为它在红外光谱范围内具有很低的损耗。呈现的层几何形状非常薄(类似于工作波长的1/50)，并且设计故意避免了有损的盖层。红外反射率测量证实了等离子体纳米天线阵列的激光诱导共振漂移。这种切换机制开启了以光学方式执行变形表面的主动、可逆和非易失性调谐的可能性。
Recently, phase-change materials (PCMs) have gained a lot of interest in the field of active metamaterials and plasmonics due to their switchable optical properties. In the infrared spectral range the huge contrast in the refractive index between an amorphous and a crystalline phase can be employed for nonvolatile tuning of nanoantenna or metasurface resonances. To make use of such concepts in devices, the reversible switching of the active material has to be realized. Here we demonstrate such reversible cycling by applying femtosecond pulses from a Ti:sapphire laser. These optical pulses trigger the phase transitions of the PCM thin film, which is covering infrared nanoantennas. Ge3Sb2Te6 is chosen as the PCM, since it offers very low losses in the infrared spectral range. The layer geometry presented is exceptionally thin (similar to 1/50 of the operating wavelength) and the design intentionally avoids lossy capping layers. Infrared reflectivity measurements verify the laser-induced resonance shifts of the plasmonic nanoantenna arrays. This switching mechanism opens the possibility to optically perform active, reversible, and nonvolatile tuning of metasurfaces.