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Novel two-photon reasonant nonlinear-optical phenomena and their application for exploring electronic structures in solids

新型双光子推理非线性光学现象及其在探索固体电子结构中的应用

基本信息

批准号：
05452035
负责人：
INOUE Kuon
金额：
$ 4.74万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

A few novel nonlinear-optical phenomena due to two-photon resonance with excited state in condensed matters are found. Those phenomena are 1) resonant second-harmonic generation in the fogeometry forbidden in the usual dipole approximation, 2) resonant hyper-Raman scattering by LO phonon, and 3) four-wave mixing phenomenon in the Brewster-angle configuration. Their profiles were experimentally studied in detail, and thereby the mechanisms have been clarified. By using these phenomena as novel spectroscopic tools, the electronic structures including biexciton in several quantum-confined semiconductors such as II-VI compound quantum wells (QWs) and quantum dots (QDs) are clarified. In particular, the band-offsets and the excitonic binding energy EX in an ultra-thin ZnSe/ZnS QW have been for the first time determined ; a prominent enhancement of Ex due to confinement is found. The existence of a biexciton is evidenced for the first time in both ZnSe/ZnS and ZnS/ZnSSe QWs. As a result, striking enhancement of the biexciton binding energies are also observed. For these purposes, new-types of spectroscopic techniques, i.e., two-photon absorption, cw Brewster-angle reflection, and transient (time-resolved) reflection of a femtosecond pulse in the Brewster-angle geometry, which dominantly reflects free-induction decay of coherent excitation, have also been developed.Thus, all those phenomena newly developed have been demonstrated to provide useful tools for exploring electronic structures, particularly in quantum-confined systems. The present outcomes have been or will be published in 8 to 10 papers.

在凝聚态物质中发现了一些新的由激发态双光子共振引起的非线性光学现象。这些现象是：1)在通常偶极近似中禁止的fogeometry中共振二次谐波的产生，2)LO声子的共振超拉曼散射，以及3)在Brewster-angle构型中的四波混频现象。通过实验对它们的分布进行了详细的研究，从而阐明了它们的作用机理。利用这些现象作为新的光谱学工具，阐明了II-VI复合量子阱（QWs）和量子点（QDs）等几种量子受限半导体中包括双激子在内的电子结构。特别是，首次确定了超薄ZnSe/ZnS量子阱中的能带偏移量和激子结合能EX；由于约束，Ex有明显的增强。在ZnSe/ZnS和ZnS/ZnSSe量子阱中首次证实了双激子的存在。结果还观察到双激子结合能显著增强。为此，新型的光谱技术，即双光子吸收、连续波布鲁斯特角反射和飞秒脉冲在布鲁斯特角几何结构中的瞬态（时间分辨）反射也得到了发展，这些技术主要反映了相干激发的自由感应衰减。因此，所有这些新发展的现象都被证明为探索电子结构提供了有用的工具，特别是在量子受限系统中。目前的研究成果已发表或将发表8 - 10篇论文。