Chen Ziyu, Dai Hongwei, Liu Jiaming, Xu Hui, Li Zixuan, Zhou Zhang-Kai, Han Jun-Bo
Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China.
Opt Express. 2013 Jul 29;21(15):17568-75. doi: 10.1364/OE.21.017568.
Au triangular nanoprisms with strong dipole plasmon absorption peak at 1240 nm were prepared by wet chemical methods. Both numerical calculations and experiments were carried out to investigate the optical properties of the samples. Finite difference time domain (FDTD) and Local Density of States (LDOS) calculations demonstrate that strong electric field enhancement and large LDOS can be obtained at tip areas of the Au triangular nanoprisms. Z scan techniques were used to characterize the nonlinear absorption, nonlinear refraction, as well as one- and two-photon figures of merit (W and T, respectively) of the sample. The results show that maximum nonlinear refractive index can be obtained around the resonance absorption wavelength of 1240 nm, detuning the wavelength from the absorption peak will lead to the decrease of the nonlinear refractive index n(2), while the nonlinear absorption coefficient β doesn't change much with the wavelength. This large wavelength dependence of n(2) and small change of β enable the sample to satisfy the all-optical switching demand of W> 1 and T< 1 easily in a large wavelength range of 1200-1300 nm. These significant nonlinear properties of the sample imply that Au triangular nanoprism is a good candidate for future optical switches in infrared optical communication wavelength region.
通过湿化学方法制备了在1240nm处具有强偶极子等离子体吸收峰的金三角形纳米棱镜。进行了数值计算和实验以研究样品的光学性质。有限时域差分（FDTD）和局域态密度（LDOS）计算表明，在金三角形纳米棱镜的尖端区域可获得强电场增强和大的LDOS。采用Z扫描技术表征样品的非线性吸收、非线性折射以及单光子和双光子品质因数（分别为W和T）。结果表明，在1240nm的共振吸收波长附近可获得最大非线性折射率，使波长偏离吸收峰会导致非线性折射率n(2)降低，而非线性吸收系数β随波长变化不大。n(2)的这种大波长依赖性和β的小变化使得样品能够在1200 - 1300nm的大波长范围内轻松满足W>1和T<1的全光开关需求。样品的这些显著非线性特性表明，金三角形纳米棱镜是未来红外光通信波长区域光开关的良好候选材料。
