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JOINT STUDY ON OPTICS OF EXCITONS IN QUANTUM CONFINED SYSTEMS

量子约束系统中激子光学的联合研究

基本信息

批准号：
05044028
负责人：
INOUE Kuon
金额：
$ 3.84万
依托单位：
RESEARCH INSTITUTE FOR ELECTRONIC SCIENCE
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
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

The purpose is to investigate the properties of exciton in quantum confined systems and to develop novel nonlinear-optical phenomena related to the excitons.1. The band-offsets in a thin ZnSe/ZnS quantum well (QW) were first determined with combined use of two-photon (TPA) and one-photon absorptions. Furthermore, a prominent enhancement of the exciton binding energy (Ex) due to confinement effect is found. Then, we have found the existence of biexciton for the first time in a II-VI QW by direct TPA,together with manifestation of a new luminescence (PL) line and the PLE spectrum. As a result, the biexcitonic binding energy (Exx) for 20 * well thickness is found to be 7 times as large as that of bulk ZnSe.2. Two novel nonlinear-optical phenomena, i.e., the "forbidden" second-harmonic generation (SHG) and hyper-Raman scattering by LO phonon both in two-photon resonance with 2P exciton are found in ZnSe/ZnS QWs. The fundamental aspects are experimentally clarified, enabling us to interpret the microscopic mechanisms.3. The properties of exciton and biexciton are experimentally studied in ZnSe/ZnSxSel-x QWs (x=0.18), epitaxially-grown on a GaAs substrate with latticematching. In addition to PL and PLE,novel methods newly-developed have been employed ; those are spectroscopies of cw Brewster-angle (BR) reflection, femtosecond transient BR reflection reflecting only free-induction decay and fourwave mixing (FWM) in the BR geometry. First, one-monolayr-terraced structure is found to be formed with each excitonic spectral width dominated by homogeneous brodening. A biexciton is found to stably exist, which is evidenced by the existence of the FWM signal in the negative delay of second pulse. It is found that Exx is almost twice enhanced as compared to that of bulk ZnSe, in contrast to that of exciton.13EA05 : 4. Novel resonant SHG and HR scattering phenomena are also found in CdS and CuBr quantum dots embedded in glasses.

目的是研究量子受限系统中激子的性质，并发展与激子相关的新的非线性光学现象.首次采用双光子和单光子激发相结合的方法测量了ZnSe/ZnS薄量子阱中的带阶。此外，还发现了由于限制效应，激子结合能（Ex）显著增强，并首次在II-VI量子阱中发现了双激子的存在，同时还发现了新的发光线和PLE谱。结果，发现20 * 阱厚度的双激子结合能（Exx）是体ZnSe的7倍大。两个新的非线性光学现象，即，在ZnSe/ZnS量子阱中发现了LO声子与2 P激子双光子共振时的“禁戒”二次谐波产生（SHG）和超拉曼散射。基本方面的实验澄清，使我们能够解释的微观机制。实验研究了在GaAs衬底上外延生长的ZnSe/ZnSxSel-x（x=0.18）量子阱的激子和双激子特性。除了PL和PLE，新开发的方法已被采用，这些是连续波布鲁斯特角（BR）反射，飞秒瞬态BR反射只反映自由感应衰减和四波混频（FWM）在BR几何光谱。首先，单单层阶梯结构被发现形成与每个激子的光谱宽度由均匀加宽占主导地位。发现双激子稳定存在，这一点可以从第二脉冲负延迟中四波混频信号的存在得到证实。据发现，Exx是几乎两倍的增强相比，散装硒化锌，在相反的激子。13 EA 05：4。在CdS和CuBr量子点中也发现了新的共振SHG和HR散射现象。