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Enhanced Two-Photon Photochromism in Metasurface Perfect Absorbers
Nano Letters ( IF 10.8 ) Pub Date : 2018-09-11 00:00:00 , DOI: 10.1021/acs.nanolett.8b02042
Xiaojun Liu 1 , Xiaomeng Jia 2 , Martin Fischer 2, 3 , Zhiqin Huang 1 , David R. Smith 1, 2
Affiliation  

Light switchable materials are essential to optoelectronic applications in photovoltaics, memories, sensors, and communications. Natural switchable materials suffer from weak absorption and slow response times, preventing their use in low-power, ultrafast applications. Integrating light switchable materials with metasurface perfect absorbers offers an innovative route to achieving desirable features for nanophotonic devices, such as directional emission, low-power and broadband operation, high radiative quantum efficiency, and large spontaneous emission rates. Here we show an enhanced two-photon photochromism based on a metasurface perfect absorber: film-coupled colloidal silver nanocubes. The photochromic molecules, spiropyrans, are sandwiched between the silver nanocubes and the gold substrate. With nearly 100% absorption and an accompanying large field enhancement in the molecular junction, the transformation of spiropyrans to merocyanines is observed under excitation with 792 nm laser light. Fluorescence lifetime measurements on the merocyanine form reveal that large Purcell enhancement in the film-coupled nanocubes leads to large enhancements of the spontaneous emission rate and a high quantum efficiency. An averaged incident power as low as 10 μW is enough to initiate the two-photon isomerization of spiropyran in the film-coupled nanocubes, and a power of 100nW is able to excite the merocyanines to emit fluorescence. The power consumption is orders of magnitude lower than bare spiropyran thin films on silicon and gold, which is highly desirable for the writing and reading processes relevant to optical data storage. By sweeping the plasmonic resonance of the film-coupled nanocubes, wavelength specificity is demonstrated, which opens up new possibilities for minimizing the cross talk between adjacent bits in nanophotonic devices.

中文翻译:

超表面完美吸收体中增强的两光子光致变色

光可切换材料对于光伏,存储器,传感器和通信中的光电应用必不可少。天然的可开关材料吸收能力弱,响应时间慢,因此无法在低功率,超快速的应用中使用。将可转换光的材料与超表面完美吸收体集成在一起,为实现纳米光子器件的理想功能提供了一条创新途径,例如定向发射,低功率和宽带运行,高辐射量子效率和较大的自发发射率。在这里,我们显示了基于超表面完美吸收体的增强型两光子光致变色:薄膜耦合胶体银纳米立方体。光致变色分子螺吡喃被夹在银纳米立方体和金基底之间。由于在分子连接处具有近100%的吸收和随之而来的大场增强,在792 nm激光激发下,可以观察到螺吡喃向花青的转化。对部花菁形式的荧光寿命测量表明,膜偶联纳米立方体中的赛尔(Purcell)增强很大,导致自发发射速率和高量子效率得到极大增强。平均低至10μW的入射功率足以在膜耦合纳米立方体中引发螺吡喃的双光子异构化,而100nW的功率能够激发花青素发出荧光。功耗比硅和金上的裸螺螺吡喃薄膜低几个数量级,这对于与光学数据存储相关的写入和读取过程是非常需要的。
更新日期:2018-09-11
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