Sergeyev Anton, Geiss Reinhard, Solntsev Alexander S, Steinbrück Andrea, Schrempel Frank, Kley Ernst-Bernhard, Pertsch Thomas, Grange Rachel
Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University, Max-Wien Platz 1, 07743 Jena, Germany.
Opt Express. 2013 Aug 12;21(16):19012-21. doi: 10.1364/OE.21.019012.
We study the nonlinear optical properties of lithium niobate (LiNbO(3)) nanowires (NWs) fabricated by a top-down ion beam enhanced etching method. First, we demonstrate generation and propagation of the second-harmonic (SH) light in LiNbO(3) NWs of typical rectangular cross-sections of 400 x 600 nm(2) and length from 10 to 50 μm. Then, we show local fluorescent excitation of 4',6-diamidino-2-phenylindole (DAPI) dye with the propagated SH signal in standard concentrations as for biological applications. By measuring the detected average power of the propagated fundamental harmonic (FH) and the SH signal at the output of the NWs, we directly prove the dominating role of the SH signal over possible two-photon excitation processes with the FH in the DAPI dye. We estimate that 63 ± 6 pW of the propagated SH average power is required for detectable dye excitation. Finally, we model the waveguiding of the SH light to determine the smallest NW cross-section (around 40x60 nm(2)) which is potentially able to excite fluorescence with a FH intensity below the cell damage threshold.
我们研究了通过自上而下的离子束增强蚀刻法制备的铌酸锂（LiNbO₃）纳米线（NWs）的非线性光学特性。首先，我们展示了在典型矩形横截面为400×600 nm²且长度为10至50μm的LiNbO₃纳米线中二次谐波（SH）光的产生和传播。然后，我们展示了在生物应用标准浓度下，利用传播的SH信号对4',6-二脒基-2-苯基吲哚（DAPI）染料进行局部荧光激发。通过测量在纳米线输出端传播的基波（FH）和谐波（SH）信号的检测平均功率，我们直接证明了在DAPI染料中，SH信号相对于FH可能的双光子激发过程起主导作用。我们估计，可检测的染料激发需要63±6 pW的传播SH平均功率。最后，我们对SH光的波导进行建模，以确定最小的纳米线横截面（约40×60 nm²），该横截面有可能在FH强度低于细胞损伤阈值的情况下激发荧光。
