Schmidt S, Mascheck M, Silies M, Yatsui T, Kitamura K, Ohtsu M, Lienau C
Institut für Physik Carl von Ossietzky Universität, 26129 Oldenburg, Germany.
Opt Express. 2010 Nov 22;18(24):25016-28. doi: 10.1364/OE.18.025016.
The nonlinear optical properties of thin ZnO film are studied using interferometric autocorrelation (IFRAC) microscopy. Ultrafast, below-bandgap excitation with 6-fs laser pulses at 800 nm focused to a spot size of 1 µm results in two emission bands in the blue and blue-green spectral region with distinctly different coherence properties. We show that an analysis of the wavelength-dependence of the interference fringes in the IFRAC signal allows for an unambiguous assignment of these bands as coherent second harmonic emission and incoherent, multiphoton-induced photoluminescence, respectively. More generally our analysis shows that IFRAC allows for a complete characterization of the coherence properties of the nonlinear optical emission from nanostructures in a single-beam experiment. Since this technique combines a very high temporal and spatial resolution we anticipate broad applications in nonlinear nano-optics.
利用干涉自相关（IFRAC）显微镜研究了ZnO薄膜的非线性光学特性。采用800 nm的6飞秒激光脉冲进行超快、低于带隙激发，聚焦光斑尺寸为1 µm，结果在蓝光谱区和蓝绿光谱区产生了两个发射带，其相干特性明显不同。我们表明，对IFRAC信号中干涉条纹的波长依赖性进行分析，可以明确地将这些发射带分别归属为相干二次谐波发射和非相干多光子诱导光致发光。更一般地说，我们的分析表明，IFRAC能够在单光束实验中对纳米结构非线性光发射的相干特性进行完整表征。由于该技术结合了非常高的时间和空间分辨率，我们预计它将在非线性纳米光学中得到广泛应用。
